UNCORRECTED TRANSCRIPT OF ORAL EVIDENCE To be published as HC 616-ii

House of COMMONS

MINUTES OF EVIDENCE

TAKEN BEFORE

ENVIRONMENTAL AUDIT COMMITTEE

 

 

CARBON BUDGETS

 

 

Tuesday 23 June 2009

PROFESSOR KEVIN ANDERSON

PROFESSOR JOHN MITCHELL OBE FRS and DR JASON LOWE

Evidence heard in Public Questions 65 - 153

 

 

USE OF THE TRANSCRIPT

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Oral Evidence

Taken before the Environmental Audit Committee

on Tuesday 23 June 2009

Members present

Mr Tim Yeo, in the Chair

Mr Martin Caton

Colin Challen

Mr David Chaytor

Joan Walley

________________

Witness: Professor Kevin Anderson, Director, Tyndall Centre for Climate Change Research, gave evidence.

Q65 Chairman: Good morning and welcome back to the Committee; nice to see you again.

Professor Anderson: Thank you very much.

Q66 Chairman: We are all familiar with your work and judgments. Can I kick off by asking why you think that the recommendations of the Committee on Climate Change, who have already given evidence to this inquiry, on targets and budgets are not consistent with the level of cuts needed to keep the rise in temperatures below 2^oC^?

Professor Anderson: The first point, which is not a point perhaps directly for the Committee, is that if we are to avoid dangerous climate change and if that is characterised as 2^oC (and that is a social or a political decision), then to avoid something that is dangerous would you think a 50:50 view of that is reasonable? For you to avoid a dangerous something do you think a 50:50 chance is an appropriate percentage, which is broadly what the committee used? I would suggest if it is a dangerous something that you are trying to avoid five per cent is still too high and one per cent might be about reasonable. That is, I think, a fundamental issue that the committee has to grapple with: why would it choose 50:50 to avoid something that is dangerous? There are some reasons, I think, why they might choose 50:50, because one per cent gives you a much more demanding target so they choose an overshoot. There are other people later who can comment as to how viable they think that is. I think it is fair to say that the scientific understanding of "overshoot" is not as robust as it is if we do not go up and then drop to a ppmv. There are some uncertainties around what that might trigger and we have to be quite optimistic that that will not trigger unforeseen circumstances that we know are out there but we do not quite know where they are, and they hold that overshoot, which I think Brian Hoskins referred to as a slight overshoot. I think 50ppmv is quite a large overshoot, and for it to be held for I cannot remember exactly what but something bordering on a century seems quite a long time and to hope that you do not trigger something else. That seems, as I say, quite optimistic. My understanding is that they use a single climate sensitivity distribution. I do not know whether that is an appropriate route to go down but again the later witnesses can explain why they did that and whether they feel it is appropriate or not, but certainly some of the work that is out there tends to use a range of climate sensitivity distributions. I understand they use a single cumulative value. We have recently discussed it outside, actually. An important point is that if you look in IPCC AR4 they generally get a wide range of emission cumulative values, a fairly specific concentration, and they have 450 parts per million, arguably CO₂ but I think it is not unreasonable to think that it is also CO₂e if you are going to link it to temperature. They have a big range of what the emissions are, how much we can dump into the atmosphere over 100 years. The bottom end of that range I understand came from the Habi Centre, and they have robustly defended the bottom end of that range, being that their model embodied a lot of carbon cycle feedback, which is a better way than lots of other people's models, and that significantly reduced the total emissions by, I think, about 27 per cent; yet the Committee on Climate Change's cumulative value is much higher. I think it is outside of the upper end of the AR4 values. You could make the argument that one is CO₂ and one is CO₂e, and that is an issue that needs to be debated. I do not think there is a simple correct response to that, but certainly it seemed a very high value used and it was a single value and I would question why would they be using a single value. Why would you not use a range for that? Turning to deforestation and food, deforestation could be as high as 25 per cent of total emissions. That was not taken into account by the committee as far as I am aware, which you could argue implicitly suggests that deforestation is the responsibility of the countries that deforest. Given that we have already deforested in Annex 1 nations, I think that is possibly not a fair allocation of those emissions, so I think for countries that do deforest (and that will undoubtedly go on) some of those emissions are the burden of Annex 1 nations and that significantly changes the budgets. They did not consider food emissions, and indeed many people have not considered food emissions, which are again very significant. Emissions from agriculture overall are a very significant proportion of emissions. They did not include aviation up to 2022 and then it was pretty much a fudge after 2022. If you add deforestation, food, aviation and shipping you significantly reduce the energy space, so when they talk about things like decarbonising by 2050 the electricity system they are not clear as to whether the rest of the system is fully decarbonised or not. I would argue that you cannot wait that long if you factor in deforestation, food, aviation and shipping emissions. I think there is a large hole in that part of the analysis which needs tightening up. The peak year we again discussed briefly outside. If I asked you when you thought global emissions were going to peak I think it is very unlikely that any of you would choose 2016 or Stern's 2015 or Paul Bear's work, 2012-2014. If the economy bounces back, as everyone apparently hopes it does, emissions will continue to rise and I think it is unrealistic, possibly naïvely optimistic, and misleading to do the analysis around 2016 as a peaking year. Many people do not think of that. They do not take account of the fact that the peaking is that early. Do we really think this country is going to peak in 2016? In the States Obama said they might get emissions down by four per cent by 2020 compared with 1990; yet they might fail so they may get nowhere on that. Generally most people miss their targets. The Japanese have said something like eight per cent, so you would expect the non-Annex 1 countries' emissions to be going up well beyond 2020, and therefore I think a peak of 2020 is still highly optimistic and fundamentally changes the results for the political world in terms of the rates of reduction that are necessary. I think 2016 is a dangerously misleading peak. It would be lovely if we could achieve it. Remember that in the UK emissions are going up and are going up very significantly. They are not going up in terms of our immediate national budget, and that is because we are buying more goods from elsewhere. If you look at the consumer index budget for the UK, published by Defra, you will see that emissions in the UK are rising, and rising very rapidly indeed, whereby a lot of those emissions are effectively in the goods we buy from countries that do not have caps. For the UK, which is probably one of the leading countries in terms of climate change, our emissions are rapidly going up because we are consuming more and more goods, so the best example out there is still going up. The other part which is important in this is the CDM. They said in the evidence (I looked through it briefly on the train this morning) that under the interim budget there is no CDM (Clean Development Mechanism). I do not think that is true because under the Emissions Trading Scheme there will be some CDM. If you look at the latest EU energy and climate change package and ally that with the Committee on Climate Change's report, under the interim budget 17 per cent of emissions we have bought from Ghana, Nigeria and other countries that have no targets. Under the intended budget 27 per cent of the UK's effort can be bought. If you add to that the rest of the EU ETS that we can buy, and everyone, of course, wants to buy out of the EU ETS, you can effectively can buy out under the interim budget 67 per cent of the UK's effort and 75 per cent for the intended budget. To me that does not seem a responsible way to go for a country that is trying to lead on climate change, that ability to buy out significantly from other poorer parts of the world that have no caps, so there is no guarantee of any emission reductions there. In fact, you might get an emissions increase, and on top of that to be able to buy from the EU ETS I think is probably irresponsible. You can already see that with Geoff Hoon announcing the third runway, for instance, and saying that emissions in 2050 from aviation will be the same as they were in 2005. On the same day his own department published a report that said there would be a 60 per cent increase in emissions, and the smoke and mirrors that allows that to occur is the buying from the EU ETS. Everyone is doing that with their airports. Everyone is doing it with all of their expansion. Everyone expects to buy in the future to allow them to build high carbon infrastructure now. There is a range of things there. Is 50 per cent fair and appropriate for something dangerous? Overshoot I do not think is necessarily the most scientifically robust route to go down. Is the single climate sensitivity distribution correct? Is the single cumulative value correct? If it is, is the high one correct? Ignoring deforestation, food, aviation and shipping - is that appropriate? Then should we be allowed to buy either the small amount you have left to do from CDM and the Emissions Trading Scheme? If you put all of those together what tends to be the case is that in everything we do we try to choose the most optimistic end of the science or the policy. If, every time you go to the supermarket and they overcharge you, eventually you start to think there must be something systematic in the fact that they always overcharge and never undercharge. If, every time we choose a number that knocks the amount we have to do politically down, I start to wonder how close plausibility or practicality is sailing to political expediency, and I am uncertain as to how much the committee, and I have a lot of time for what they have done, have been driven by what they think the political orthodoxy is prepared to face. I do not think as an independent committee that is their responsibility.

Q67 Chairman: You have raised plenty of issues in that answer. Just picking out one or two things, first of all on the point about the 2^oC, given all that you have said, what level of cuts would we require to make to keep the temperature rise to 2^oC?

Professor Anderson: For the UK or globally?

Q68 Chairman: The UK to start off with.

Professor Anderson: For the UK it would depend on how you apportioned emissions. At the event I was at last week with some of the facilitators from the less developed countries they suggested that we should have cut to zero emissions a few years ago because they would say there is a massive burden historically. We already have a debt to them of what we have emitted, so it depends enormously on what apportionment regime you go for. I know a lot of the LDCs now are saying that we should pay for historical emissions. If that is the case you will have to find some form of sequestration or you buy enormous amounts of emissions from them at some very high carbon price, I would say, to make it fair. I do not think there is an easy answer to that. If you believe in historical emissions and our responsibility for those then we have to cut immediately to zero. If you think, "Let us forget historical emissions; that is the past", if you take from 1992, from Rio, we knew from there, or if you take from 2000, you can then do some apportionment regime, and, depending what apportionment regime you do, you will get different reduction rates. One of the papers we have produced would say six to nine per cent would be reasonable for the UK if we peaked in the next few years, say, 2012, 2014. Six to nine per cent per annum reductions from energy would be about right because remember we have to factor in food and you have to say what do we do about deforestation. I do not think the committee took those into account. They have 2.8 per cent reduction, I believe. If they took deforestation and food into that and then said what is left for energy, even for them there would be a much tighter reduction rate than that.

Q69 Chairman: That would be quite challenging. Is there any point in our doing that unilaterally?

Professor Anderson: It depends on your moral framework, really. Do you want to show leadership or do you want to go down with the Titanic? That is purely a political decision. I know where my views on that are. I think the climate change community has not served the policy makers well, either in terms of demonstrating leadership or often in terms of directly giving their message to policy makers. I think it has often been softened, to be honest. I think we have all chosen to go down the route of least resistance and I think that if we are going to show leadership we have to move away from that, both in the scientific community and the political community. I see no evidence of that at the moment.

Q70 Chairman: The Committee on Climate Change has to operate in the real world, the political world and so on. Is it more realistic to talk in terms of trying to reduce the risk of a rise of temperature of 4^oC to very low levels? Is that a more realistic and meaningful aim than for the Government to continue talking about keeping the rise to 2^oC, which seems now very unlikely to be achieved?

Professor Anderson: I take the view, and I have done for several years, and I know that Bob Watson from Defra now takes this view, that we should all-out aim for 2^oC in terms of mitigation but we should adapt for something considerably higher. At 4^oC, as I understand it, and again some of the later witnesses are more expert on this than I am, you do not stabilise, so you have got to see ongoing increases from there. I do not think we can survive in any social form that we recognise globally at 4^oC. A one metre sea level rise takes out about a third of Bangladesh; 35 million people live there. It takes out all of Orkney pretty much and lots of the low-lying parts of the world. We would all be impacted by that one way or another. I think if we go down the 4^oC route it is completely morally irresponsible and I think we would rue the day but we would be able to do nothing about it because we will set that in train over the next few decades. That is why it is absolutely essential we make the right decisions now. I do not think 4^oC is the right route to go down. However, I do think we have to do adaptation, particularly for poorer parts of the world, at 4^oC. Do not build any city below a 10-metre sea level rise.

Q71 Chairman: We are happy to address adaptation issues in the autumn. Just finally on this section, you characterised a 50 per cent likelihood of exceeding 2^oC, if we think that is dangerous, as a pretty hefty percentage. Do you therefore regard it as really necessary that we should aim for a much lower concentration of greenhouse gases in the atmosphere in order to reduce that 50 per cent likelihood of exceeding 2^oC?

Professor Anderson: Yes, I do. In the same way that the Committee looks at these things in a practical way as well, I see no evidence that we are prepared to make those changes to our lifestyles, but yes, I think we should be aiming for something much lower, and certainly 400 would be to me to be the upper end of what we should be aiming for, but that would mean absolutely fundamental changes to our lives this afternoon and we are not prepared to make any of those changes; I see no evidence of any of us doing that, so, yes, I do think 400 would be a far more appropriate target to aim for.

Q72 Joan Walley: You say you see no evidence of people making changes to their lives this afternoon. That really brings it home, does it not, and yet we are talking about a trajectory that is taking us with budgets up to 2022?

Professor Anderson: Yes.

Q73 Joan Walley: How would you reconcile this really complicated five-yearly budget set 15 years in advance between now and 2050 and the immediacy that we need to make changes this afternoon?

Professor Anderson: At the moment I do not think they can be reconciled. In terms of the budget approach, and again all credit to the Committee here and indeed to the whole parliamentary process, it has shifted away from the scientifically illiterate view of long-term targets to a scientifically robust view of cumulative emissions; at least it has significantly embraced that approach, not fully but significantly, and I think that is a real improvement, so the budgets are a real way forward. However, I do think that the policy framework, the social framework, to bring about what has been put into the budgets laid out by the committee is completely lacking. For instance, I was at the Climate Change Conference in Copenhagen this year where 2,500 of the world's scientists flew to Copenhagen to tell the rest of the world about how urgent climate change is. These are the people who are fully informed who are making no changes to their lives on average. In fact, I would think almost certainly their emissions will have gone up every year for the last ten years. The people who know the most about it, with the most amount of information, somehow think they are the group that should not respond. The civil aviation industry thinks that, the shipping industry thinks that, the car industry thinks that. Every sector thinks it is the unique sector. Every individual thinks they are the unique individual that should be the exception and everyone else should make the changes. Whilst the budgets are there, there is no political structure to make those significant changes from all of us. We think that we are the reasonable person and everyone else is not.

Q74 Joan Walley: But we need to be confident that there is an agreed level of effort that fits into that public framework and into that social framework, and I do not see how we can be confident that that is going to be there to get us on to the emissions pathway, given the complete lack of interest and awareness that there is about this one core issue.

Professor Anderson: I would agree but do we despair or do we say --- that is the reason we have meetings like this. That is the reason people are engaged in this process, trying to drive the whole process forward. It is not in my view going in the right direction in any way, shape or form yet but there is a thin hope that we can get some conversion there. I think it will require really dramatic political leadership, way beyond what currently we have been discussing. It is all very well putting the budgets in place but the mechanisms to bring about those changes simply are not there. I do not think the public will is there either. Actually, I think the politicians are way ahead of the journalists and well ahead of the public on this, so I think some credit should be given to the politicians that have been engaged in all of this process, particularly for the UK here. However, still I see no real drive towards this. The only hope we have at the moment is that bankers have really screwed up our economy, because growth globally is now down 2.9 per cent over this year. Emissions will have come down. The only time emissions come down is when you have a hit on growth, so after September 11 you saw emissions globally come down. Now you are about to see emissions come down. Until we are prepared to accept the fact that you cannot reconcile the rates of reduction we now require with economic growth in the short to medium term whilst you put low carbon supplies in place we will not get the rates down to levels that match the budgets that move us towards 2^oC.

Q75 Joan Walley: And you are saying that we should have a continuous trajectory all the way up to 2050?

Professor Anderson: Yes, but, obviously, the further out you go the more you hope to be able to understand. Yes, broadly the committee had that. They drew it out to 2022 and then they drew a vague dotted line out to some 80 per cent reduction by 2050 and some sort of discussion about aviation and shipping. It was certainly a start but, as I say, it did not take account of food or deforestation. Those issues were not considered and aviation and shipping are a fudge at best. They have made a very good start but there is a long way to go to make that more robust. However, I still think it gives a really clear political signal about what we need to do now.

Q76 Joan Walley: You mentioned just now about the political orthodoxy of the Climate Change Committee. Do you feel that it is limiting its recommendations in terms of what will be accepted by governments or do you think that it is showing the leadership that it should be showing?

Professor Anderson: It is showing some really important leadership on the emissions issue. Moving away from long term targets (at least to some extent) towards cumulative emissions is a big improvement, but, reading through the evidence that was given here from the committee, the words "practical" and "plausible" kept coming up all the time. I get this everywhere I go - "That's politically unacceptable". My guess is that living under a metre sea level rise is politically unacceptable. There is an assumption that because the orthodoxy will not allow us to mitigate to a certain level so that is unacceptable then there is no cost to that. If we are not prepared to accept that we are inherently then accepting the high level adaptation or complete displacement of some economies. The future is unacceptable and there is no acceptable route out of that. In fact, if anything looks politically acceptable at the moment it is unlikely to work. One of the metrics of political unacceptability is a requirement of whatever future we go down, and we have got ourselves into that position. We are in 2009 and our emissions in the UK and globally continue to rise. We have known about this since 1992 at best. We have been talking about it ad infinitum since 2000 and we have done absolutely nothing. We have got ourselves into the position knowingly and now we are faced with really difficult choices because it is cumulative emissions approach, not a long term target approach. We have no-one to blame but ourselves for this.

Q77 Joan Walley: Just finally from me in this series, do you believe that the work that the Climate Change Committee is doing in terms of that trajectory is now sufficiently factored into the work that is being done to overcome the difficulties because of the recession?

Professor Anderson: I think the answer to that is no, and I do not blame the committee or anyone else. We do not know how to bring these things together as yet but I think it is really important we start to link them together. I think there are some interesting lessons from what we call a recession. Unfortunately, I do not see how the Annex 1 countries can continue to see economic growth and reconcile that with the rates of reduction necessary for anything like 2^oC. I think we have to learn lessons from how to distribute the pain and suffering of a recession more fairly because I think we have to go through that, particularly in the Annex 1 wealthy countries, in the interim period over the next ten or 20 years for us to have any hope of the sorts of reduction rates that are necessary.

Q78 Mr Caton: You have already mentioned the Committee on Climate Change's interim budget which the Government has decided to follow until there is a global deal when the EU moves to a target of a 30 per cent cut by 2020. What are the risks associated with following an interim pathway rather than the intended pathway?

Professor Anderson: Quantitatively I think it is very difficult to work out exactly what that would mean because the risks relate to the global budget and that does not say anything necessarily about the global budget but I think there is a significant risk in terms of leadership. I did not quite understand the first response from David Kennedy on this. If you claim to have a view as to where we need to go for 2^oC you cannot say that if the rest of the world does less we will do less as well. That is not coherent. If the rest of the world does less you have to do more to move you to towards 2^oC, so they are not being driven by that; they are being driven by what they claim to be the political realities of the world around them. There is therefore a danger for the interim route. It is an easier route and it again sends a message to everyone else that we are not prepared to demonstrate the leadership that the intended budget would have shown, so I think there is a risk there in that we should have shown that leadership, though I have to point out that a 27 per cent buy-out for the CDM significantly reduces the benefit of having an intended pathway.

Q79 Mr Caton: If we end up keeping the interim budget right the way through to 2022 how much steeper will we have to cut UK emissions after that date?

Professor Anderson: The difference between the intended and the interim is very small. We produced a report which, if the Committee has not had it, I am happy to pass on to you, which shows that difference. It plots the graphs out to 2050. The difference between the intended and the interim is not particularly large in terms of the cumulative emissions. It is a matter of just a few per cent difference, so it is not that significant.

Q80 Mr Caton: So we need a tougher budget than either the interim or the intended?

Professor Anderson: Oh, yes. I think the EU should be going for something like a 40 per cent reduction by 2020, and I am not even sure whether we should take that on a consumer basis rather than a producer basis. If we keep exporting our emissions to China and elsewhere that have no caps I do not think that is necessarily appropriate so I think we should consider taking a consumer basis for our emissions from the OECD countries, from the EU, and we should look at a 40 per cent real reduction by 2020. It will do two things. It will send a far clearer signal to the LDCs to sign up to something significant in Copenhagen, which they will not do unless the Annex 1 countries show real leadership, which we are not going to show, I think, so we would have to make those sorts of levels of reduction, and we cannot keep assuming that we only look at our immediate at-home emissions. We have to take account of the fact that a large proportion of our emissions come from other parts of the world.

Q81 Colin Challen: Can I come back to the question of aviation and shipping and ask whether there is a logic in including them in the targets but not in the budgets?

Professor Anderson: There is a logic to some extent with shipping. I do not think there is for aviation. We know everything we need to know about aviation in terms of CO₂ emissions. It is robustly quantified, we know all of that data, we know where the airport is setting off. We have a reasonable way of apportioning emissions 50:50.

Q82 Colin Challen: But there is no agreed way of apportioning emissions.

Professor Anderson: The UK broadly accepted that when it worked out its aviation emissions. It works them out. It already has ways of quantifying these numbers. The EU is very likely to accept exactly that particular route of 50:50. If you take all landings, all takings off or half of all return flights and add that cumulatively round the globe that works, it adds up to the full number, so we all accept that. There are big issues about uplifts, the other factors of aviation which we can come back to if you want to discuss that, but I think aviation could have been factored into the budgets from now, and I think should have been factored into the budgets.

Q83 Colin Challen: Has it been factored into the budgets?

Professor Anderson: Yes.

Q84 Colin Challen: What difference has it made? Is it significant?

Professor Anderson: For the UK aviation is just under seven per cent of UK emissions and growing. Aviation and shipping, if you add them together, have roughly the same emissions as private cars. It is like saying let us ignore private cars. I think most of us would suggest that that is not a reasonable approach when we look at CO₂ emissions, to ignore all cars. It is a very nice proportion for the UK, very different from the numbers globally. As I say, it is a little under seven per cent. Given that that is a sector that is growing very rapidly and, you could argue, is being promoted to grow by certain planning rules that allow expansion of airports and so forth, and given that the emissions from aviation are looking to grow significantly whilst at the same time we are supposedly going to reduce emissions from elsewhere, they very rapidly become an even more significant proportion of the emissions. I think to ignore aviation therefore is again a dangerous omission that we knew about. We did not have to do that. Often people say aviation and shipping are the same thing. They are not. First, the shipping data is all over the place whereas the aviation data is not. Secondly, it is really hard to know how you apportion shipping emissions. If a ship brings apples from New Zealand to the UK but on the way runs off to Venezuela and picks up chickens to drop off in Holland, how do you apportion those emissions? These are things that are not well understood. Some of the emissions data estimates on shipping are twice some of the other estimates, so there is a huge discrepancy in shipping emissions and we do not know how to apportion routes that are not clear. Ships bunker fuel. They go to a particular port just to put on lots of fuel because it is cheaper and they can carry it round at no real energy penalty. Aviation cannot do that. Shipping is more complicated so we definitely should have included aviation. I think it would be reasonable to make a fudged guess as to what shipping might be and have it there as a proxy number.

Q85 Colin Challen: How long do you expect it to be before the shipping problem has been resolved? Which carbon budget should we be aiming to include shipping in?

Professor Anderson: There is quite a lot of discussion about whether shipping should be a country in itself, and I think there is some logic to that, to say that it is such an awkward, difficult sector that perhaps it should just trade within its own boundaries. I would suggest, if we do that, that it is not allowed to buy emissions from anywhere else and we give it a very stringent emission reduction pathway. It will want to buy out from elsewhere; everyone wants to buy from elsewhere. I think there is some argument to be said for shipping being its own country and that it has to reduce its emissions at whatever, six per cent per annum, and let it do it however it feels fit. Let the market for shipping determine how to do that, but I am very reluctant to say that it should be allowed to buy from other parts of the world or from other sectors.

Q86 Joan Walley: Given the importance that you are adding to shipping, have you engaged in discussion at all with the Chamber of Shipping or with Lloyd's List?

Professor Anderson: Yes.

Q87 Joan Walley: What response have you had?

Professor Anderson: I have had some engagement with them myself, not a lot. I should express an interest. I served my time as a marine engineer in the Merchant Navy so I am responsible for a lot of the emissions from these ships that bring our goods over here. One of my colleagues in particular has been discussing things with the various shipping organisations for quite some time. They are quite keen on the idea of there being a separate sectoral emissions budget for shipping. They want to be able to buy from elsewhere though. That is where we would probably to some extent differ from their view, but they think there is some merit to be had from being separate. I think at the moment we may broadly hold with that because it looks very difficult to know how you add it to a national emissions budget. Myself and my colleagues, who have been looking at shipping for some time now, would probably agree with their view but you cannot buy out from that cap.

Q88 Joan Walley: The reason for my question is that there has been some concern expressed within the shipping industry about a recent report of this Committee and I just wonder where the informed debate is within the shipping community that could bring forward the leadership that is required at all kinds of different levels, including within the shipping sector.

Professor Anderson: I think it is still an uninformed debate at the moment across the board on shipping. We do not know the data. The raw data is missing. We have not as yet been able to track the routes particularly well. We know what happens in ports but we do not know the routes by which ships come here. We know that ships bunker fuel all over the place. We do not really understand that, so at the moment we do not have a lot of data, but I do think, as I said before, that we are in a position now where we could start to set up a mechanism for shipping to work within its own remits whilst we tighten up the data side.

Q89 Joan Walley: And that would include the IMO, would it?

Professor Anderson: Oh, yes.

Q90 Colin Challen: I have been listening to your evidence. It feels to me like, whilst you say you respect the Climate Change Committee and give it due credit, nevertheless what it is recommending is complacent, or is it worse than complacent?

Professor Anderson: As I said, I think they are being too much influenced by immediate plausibility and political realities.

Q91 Colin Challen: That is part of their remit, is it not?

Professor Anderson: It is, but it is also to be informed by the science. If immediate political realities cannot be reconciled with the science which side do you come down on? The role of the committee in my view is to be an independent committee that is significantly influenced by the science and less by the political realities. That is the role of politicians; that is what we appoint them for. If the committee ends up being another filter between the science and the politicians that is completely inappropriate because there are far too many filters between the science and the policy makers already. I think the role of the committee is principally to be driven by the science with some awareness of some of the broader political issues that are there. I personally would like to have seen the committee being a scientific committee. I wish it had not got any economists on it. I do not think that is the role of the committee; that is the role of economists and the Government, to deal with those issues. I think they should have been given as impartial summaries of the science as possible, and I do not feel that is what the committee has done. It has looked at what is politically acceptable. Maybe I am wrong on this but it does seem to me that every time they choose something that is at the much more optimistic end of science you add all these together and you come up with a result that says, "Hey, this is just about doable within the political orthodoxy, a bit challenging but we can do it". That just feels a little bit too convenient.

Q92 Colin Challen: So you are saying that the Tyndall Centre's approach and their approach are using the same figures but they are simply taking a more generous view of what those figures might permit?

Professor Anderson: Yes. Somebody might say we have taken the opposite end of the spectrum. I hope we have not, and I would be pleased if people could point out where we have. I hope what we have generally tried to do is take almost like the orthodoxy in terms of the science. For instance, we take no account of tipping point issues. We have not factored in aerosols. We have also not factored in uplift issues from aviation which would be very significant for the UK. We have taken almost the most conventional form of the science and the results are still politically very demanding. I do not think the rest of the nuanced issues around it are very important for the policy debate. I think we are very clear which route we should be going down, and yes, taking the sort of approach we have taken, taking the orthodox data that is out there across the full range and allying that with things that most people ignore, like deforestation, food, peaking after 2016, are absolutely central issues. You come up with very different results, but if the committee had done their analysis with a peaking of 2020 their results would not be hugely different from ours, I do not think. They would be very similar. That peaking date is absolutely essential to understand how important that is, and whether you think 2016 is an appropriate peaking date. The other bit they did not do any real work on, they say they did not even consider it particularly, I saw in the responses, is about apportionment. They must have used some form of apportionment of global emissions to the UK to develop any UK budgets but they certainly did not take account of any historical emissions in there, so that apportionment issue is another one that the committee have glossed over and it needs to be more thoroughly investigated.

Q93 Colin Challen: On that point they have said that they have used a C&C approach, sort of; they do not actually use contract and converge as contract and converge. This peaking date is clearly important for future emissions, say, after 2020, because it is bound to have a significant impact. What difference does it make to the post-2020 trajectory, having these different dates between 2015 and 2020 itself, and could you perhaps also say something about the impact of the recession on the peaking date because I have read that the recession would have a six per cent reduction impact on global emissions. Maybe that will impact on when we should have the peak year for emissions.

Professor Anderson: I will comment on the last point first, the recession. I think it is very difficult to say. The estimate is now that growth will drop by 2.9 per cent. You would expect emissions reduction to be a little bit less than that over a year, not more, but, of course, everyone is trying to push the economy back up. There is a bit of rhetoric about this, about some green growth, and particularly OECD countries, in terms of their reflation packages, are putting virtually nothing into green growth. The places that are leading on that are places like South Korea and China. They are putting about a third of their reflation packages into meaningful green growth. We are doing nothing, the rest of Europe is doing nothing and the States are doing nothing. It does appear that everyone is trying to drive forward out of the recession as quickly as possible to get back to the old pathway, so, yes, this will be a step. You will go up, emissions will stabilise or maybe drop a little bit for a couple of years or so, and if we can actually drag ourselves out of recession, which is the goal of all these economic reflationary packages, we will go back on the old pathway as quickly as we possibly can and then we will start to think about climate change and the environment again, probably. Arguably, if we have a stabilisation of emissions for two years, we have reached the peak and then we go back up again, that will adjust when you might think that peak should be. I would still suggest that we should not move 2020 out to 2022. I still hold to the view that we should go for 2014, we should go for this afternoon as the peak. The sooner the peak the easier it is for us to achieve. I just think it is unrealistic to keep doing the analysis on 2015 and 2016 when almost all of us accept that that is so unlikely to occur because 53 or 57 per cent of global emissions come from the non-Annex 1 countries and those emissions, quite rightly, are going up very rapidly because that is a sign of their improved welfare and development. Our emissions are also going up, so everyone's emissions are going up. There is no sign of any sense of urgency towards 2016, so I think it is more realistic to choose 2020. I would not want to see that pushed back to 2022 because of the recession. I think 2020 is just about doable. I did not quite get your first point on that. You said if we peaked in 2020 what would be the emissions reductions afterwards.

Q94 Colin Challen: If we delay the peak it is bound to have an effect on the cumulative total in the atmosphere by that point. Therefore, we would have to have more severe reductions following 2020. It leads on to my next question, which is about our annual reductions pathway. If we peaked this afternoon at two o'clock what would be our annual reductions target, do you think, from such an early peak? If it were to be delayed until 2020, from that year on what impact would that have on the annual reductions that we would have to make, if you have done that calculation?

Professor Anderson: Not without a computer in front of me. If we could peak now or in the next few years the reduction rates are going to look not too dissimilar from the ones outlined by the committee, probably a bit steeper than that. This is looking at it from the UK perspective. If the whole globe peaked and you attributed the emissions to the UK in the way that the committee have done, then a two or three per cent per annum reduction rate would seem not unreasonable, but remember that that is for all emissions. That includes food, if it is not taken out of it, and they have not included deforestation which I think should be factored in there. Therefore, on any view it would still be somewhat steeper than that. It is probably reasonable to say three to five per cent for energy if we could peak now. If we go to 2020, and then if we take out food and deforestation out of 2020, basically the rate of reduction is double figures. You decarbonise almost immediately. The difference is an infinite reduction rate pretty much after 2020 for energy, if you want to hold any reasonable chance of 2^oC, because the rest of your emissions that you will be permitted after that would have to go into food and would be taken out also by deforestation. I think if we leave it to 2020, and we tried to show this with some energy curves in the paper, you would have to completely decarbonise the global system, even if you were really optimistic, by about 2035, 2045. That is assuming the upper end of the cumulative values for 2^oC. If you think it is reasonable to assume that the non-Annex 1 countries would be allowed to use energy after us, fossil fuel based energy, and I think that was a reasonable assumption in the past, then we would have to decarbonise well in advance of 2035, so 2020, 2025. As I say, it is almost a vertical drop if we globally peak in 2020 for Annex 1 countries or you fail to meet 2^oC or any reasonable chance of it, which I think is far more likely.

Q95 Mr Chaytor: The revised EU ETS Directive for Phase III weakens the cap quite significantly. I am interested in what you feel about the balance between allowing Member States to purchase allowances within the trading system as against the proportion of their reductions that could be achieved by purchasing offset credits using CDM.

Professor Anderson: I think CDM should not be allowed. I completely disagree with any CDM.

Q96 Mr Chaytor: Why?

Professor Anderson: First, if the CDM countries have caps, that is fine and if it is a cap structure that is apportioned around the globe based on some underlying premise like a certain Community value for 2^oC and you apportion that out in a way that everyone accepts, then fine, you can have CDM, but that is not what CDM is about. CDM is buying emissions from countries that have no caps.

Q97 Mr Chaytor: But, following Copenhagen, there may well be the possibility of some caps being agreed by non-Annex 1 countries. If there were a deal that led to that then that would change the situation over CDM.

Professor Anderson: Yes. There is a slightly more nuanced point in this, but if there were a deal that led to emissions caps for all nations around the globe, and if those emissions caps were all premised on the same underlying scientific approach and the same target, 2^oC or whatever that target might be, then I think you could argue that CDM is a workable mechanism, because if we buy a tonne off them they cannot emit that tonne. However, if there is no cap and we buy a tonne off them the important thing to remember is that CO₂ is in the atmosphere for a long period of time. We keep hearing about this additionality thing, "We can guarantee the additionality". Over 100 years? That is how long the CO₂ is in the atmosphere for. You get these sorts of things, "We will put some wind turbines up and displace something else", but those wind turbines will give access to electricity that gives access to a television that gives access to adverts that sell small scooters and then some entrepreneur sets up a small petrol depot for the small scooters and another entrepreneur buys some wagons instead of using oxen and the whole thing builds up over the next 20 or 30 years, so it is the same thing. The additionality test would be, if you can imagine Marconi and the Wright brothers getting together to discuss where they will be in 2009, easyJet and the internet will be facilitating each other through internet booking. That is the level of additionality certainty you would have to have over that period. You cannot have that. Society is inherently complex. The CO₂ is there for that long, so additionality is a meaningless concept in a complex system, which society is over that sort of time frame, so CDM has no validity as a mechanism for reducing CO₂ emissions in the absence of caps. It may have validity as a mechanism for providing funding to other countries that deserve that funding, in my view as reparation because we have stopped them going down the fossil fuel route and we have also imposed very significant climate change impacts on them, so it is not aid; it is reparation, but if that is used as a way to allow us to do the things we want to carry on doing then that is completely inappropriate. That is why I am fundamentally opposed to CDM in the absence of caps. When it comes to the EU ETS, it is okay if you buy off that but you have to think that, if everyone is going to buy off it, like you are using the reason for why you build the third runway: you buy it off the EU ETS, and no doubt every other airport is doing the same thing, how viable is that as the caps tighten up in the future? Are we locking ourselves into high emission infrastructures we cannot get out of?

Q98 Mr Chaytor: Is that not the purpose, to encourage more people to buy through the allowances so the price of allowances will go up, which is the biggest incentive for them to invest in low carbon infrastructures?

Professor Anderson: Within the EU?

Q99 Mr Chaytor: Within the EU.

Professor Anderson: Yes, the price will go up but -----

Q100 Mr Chaytor: But the consequence of more people buying the allowances will drive the price up.

Professor Anderson: You are quite right, so every nation invests in massive airports, buys all the new A380s and the new Dreamliners when they come out, and then turns round and says, "Actually, we have bought all of these things. We cannot fly them any more because we cannot, unfortunately, switch them over to hydrogen". There are biofuels but there are massive concerns about biofuels and they also wax at altitude so it is difficult to fly with biofuels, so we will have built all of this high carbon infrastructure and then somehow we are going to have a political system to say, "That is perfectly okay. We will just leave that to one side. We do not mind having spent all this money on it. We are not going to use it". As soon as we have built these things we will find every mechanism out there to allow ourselves to be able to use them and show no leadership. The idea that we are going to deliberately set up a high carbon infrastructure because we can buy out elsewhere and then in the future somehow we are going to make that redundant well within its lifetime is a complete waste of capital expense when we could be improving the tram systems and lots of other things in our countries that we are lacking. I think it is an irresponsible route to go down. I think Hoon's comment is a really good example of exactly what all the countries will be trying to do. They will be gaining the whole system to allow them to carry on doing what they historically have done. They appear in discussions about we can have power stations without CCFs, the idea that they might retrofit in the future. All of these sorts of things and the emissions that come from that allow us to buy out of the EU ETS. Germany will be saying that, Poland will be saying that, everyone will be saying that, and all that will happen is that you will weaken the national allocation plans so the emissions will get weaker and weaker because every country will be arguing as to why they cannot make the changes.

Q101 Mr Chaytor: So you are not opposed to the trading scheme itself but should there be a cap on the amount that individual countries can buy through the trading scheme?

Professor Anderson: There is a cap now. Obviously, it is only the traded sector. I do not have a problem if the cap is tight and we had a very clear of where that cap is going, because then we would know, if we built these things, to some extent what the prices might be. We have no idea what the cap is because it is a horse trading process; we all know that. They are all horse traders, so the more high carbon infrastructure every country puts in there the more they are all horse trading, the weaker the caps will turn out to be and we will end up with the pretty meaningless system that we have got now. I like the EU ETS as a mechanism within the EU; I do not think it would work globally, but it is fundamentally flawed and it is far too weak. The other thing, and this is an important point that needs some more research, is that the assumption at the moment is that a tonne is a tonne is a tonne. I think buying a tonne from CDM is not a tonne at all; it is nothing to do with climate change, but buying a tonne from the ETS is still assumed to be, "We buy a tonne from there; it is the same as us emitting a tonne here". I do not think that necessarily holds. If the UK has a very strong view that 2^oC has a certain probability as the way it should go and it works out its own pathways, the EU does not have that as its premise. At the moment it has a traded sector and some ad hoc policies for the non-traded sector, so the overarching structure of the science and the regime within the EU is not as robust as that for the UK. For a robust regime to go to a non-robust regime and claim that a tonne is a tonne seems to me not appropriate. If you imagine a country that really believed in 2^oC and another country that really believed in a 6^oC future, is it appropriate for the 2^oC country to buy a tonne out of the 6^oC country? They are not the same thing. This country would have to make no changes. I think that if the UK wants to show some leadership, which it claims it does and I would argue it is doing, it should not buy it out of the EU ETS on a tonne-by-tonne basis. There should be some proportionate cap so that every time we buy it there is only 0.8 of a tonne or 0.7 of a tonne.

Q102 Mr Chaytor: Just on this method of accounting within the carbon budgets, what is the significance of us using the allowances as the means of accounting for progress rather than the actual emissions? Is there a significant difference between allowances and emissions?

Professor Anderson: I do not know the answer to that one. My view is that we should take the emissions as what we should be assessing our progress against, not just home emissions but emissions that relate to consumption as much as production, the emissions data Defra has had produced for itself already. It is public if you go and search for it but it does not make it openly public that UK emissions are basically doing that. It always tries and says they are going down a bit, so I think we should take the consumption emissions as well as production emissions but it should be the emissions that matter.

Q103 Colin Challen: Do you think there have been any major scientific developments which perhaps the Climate Change Committee has not taken into account? I am thinking particularly of the IARU Conference in Copenhagen in March and its conclusions which have just been published.

Professor Anderson: Undoubtedly the science is changing. Anyone who plots a learning curve, and we have all been plotting these things for years, would be able to tell you that whatever we think was fairly good before becomes bad now. The situation gets worse and worse. There is no learning curve, so what is coming out of Copenhagen is that it looks like the impacts for 2^oC are probably at the worse end, and no doubt they will not be appropriate for 2^oC; they will be appropriate for 1.5^oC. We have not learned from this. All the time we underestimate the scale of the problem and the scale of the adaptation issue and the impacts and the scale of the mitigation issue, and we have no learning curves there at all. We get burned every time and we put our hand back in the fire again and we will no doubt do it again. What is happened is that the science has changed. The science says, yes, things look even more demanding than they were before. Originally people used to talk about 550 for 2^oC and that has gradually moved towards 450 and some people talk about 400 now. You can almost plot that pathway and I think we should be aware of that. This is my concern with the Climate Change Committee. It errs on the side of optimism and yet the learning curves say you should err on the side of pessimism.

Q104 Colin Challen: Should it somehow be more flexible, able to respond more quickly, because I do not think they are going to publish another report on these initial conclusions for quite some time? As I say, they have done their main body of initial work which will carry us through politically for quite a period of time. There seems to be a mismatch there in its ability to quickly update the Government on changes that might be necessary to budgets.

Professor Anderson: I would hold that what it should have done in the first place was take more a pessimistic view than an optimistic view and then it should not have to revisit the science too often. The concern about revisiting the science is that science is inherently an iterative, uncertain process, and that is what is good about science; it is not a black and white view. Therefore, you have to be quite careful of any process that keeps coming back to revisit the latest science because the latest science is likely to be wrong or not quite as it seems in a couple of years' time. I would be a bit cautious about approaches that kept going back to the science and revisiting the budgets, but I think if we had started off in the first place by taking a far more practical view (and they would probably argue that politically it was not very practical), if we had taken a more negative end of the spectrum, I think that would have held us in good stead as the science changes out in the future and it is very likely to carry on down that learning curve as things are going to get worse and worse. If you had done that in the first place you would not have to keep revisiting the science, but it is really important that we do revisit the science. One of the big issues that came out, particularly in terms of the poorer parts of the world, was acidification, that at 400-450ppmvCO₂ you are going to see some very significant acidification issues. We do not know quite what will do to fisheries and things like that, but a lot of the poorer parts of the world are really dependent on things like their local fisheries and those sorts of impacts are potentially catastrophic for some of these economies and societies and I do not think they have been factored in sufficiently well. There are some really important issues we need to think through. For instance, DFID's role might be to think about those sets of issues to do with how the aid budgets reflect the change in acidification; are there issues that need to be thought through there, or the adaptation to the areas that rely very heavily on fishing to other forms of support for their economies? There are issues that come out of that that may affect other things than just mitigation. I think the committee should probably have taken a less optimistic view, possibly a more demanding view, than they did and therefore they would not have to keep revisiting the science so often.

Q105 Colin Challen: But that would require far more demanding budgets and some kind of crash programme of public works, et cetera?

Professor Anderson: It would, yes. We have no problem investing trillions in the banks. You must have heard this over and over again; people go on about this now. We have been arguing for a few billion pounds here, there and everywhere. There is never any money around. As soon as the banks go pear-shaped there is trillions that somebody found, so we can find trillions to deal with things but we cannot find a few measly millions or billions to deal with supposedly one of the greatest threats that we face, so, yes, I think there should be a massive investment programme in all sorts of things to drive things in a different direction, but we have unfortunately spent the money on the banks.

Q106 Mr Caton: You accuse the Climate Change Committee of being over-optimistic. Recent history shows the Government has been even more over-optimistic in its forecasting. What are the main lessons that it needs to learn now for the future of the UK climate change programme, given the disappointing progress towards the 2010 target for a 20 per cent cut in CO₂ emissions?

Professor Anderson: The lessons that we all know. Everyone is always so optimistic. They say it is just a learning curve. We can look at that learning curve. The committee has been far too optimistic, the Government has been far too optimistic, the globe has been far too optimistic. So many people will be relying on Copenhagen as if something worthwhile is going to come out of Copenhagen. I hope something worthwhile comes out of Copenhagen. It looks extremely unlikely that that is going to happen and very few people I know who are senior people involved in the negotiations there think anything significant is going to come out of it, so we need to be thinking a bit more realistically about where things are going, and if you do that you come out with the sorts of things that Colin is talking about here, almost like a Marshall Plan. That is the sort of shift that we are going to have to see but we are not going to do that. We are going to come up with as much optimism as possible that allows us to carry on with the orthodoxy, so until we are prepared to recognise that all we are doing at the moment is preparing to recover the deckchairs on the Titanic in preparation for moving them. We are not even at the moving the deckchairs stage, let alone pointing the ship in a different direction. We are so far removed from the scale of the problem and we are so reluctant, all of us, to address this because it affects us personally, it affects our economy, the way we live our lives, our attitude towards other people, that at every level we try to find anything we can to avoid that, whether scientifically or politically. I do think we are far removed from this, and this is almost an issue of culture and philosophy as much as it is now of science. In some respects the mitigation agenda is well understood from a science perspective. The science has got to tell us a lot more about the adaptation agenda as yet but I think for mitigation we know what we need to do. The problem is not lack of engineering, the problem is not lack of science; it is lack of will. I think it is far more of a cultural, political, philosophical issue now than it is one of science and engineering.

Q107 Joan Walley: You have said what is wrong with how we are going forward but, given the policy framework that we are currently operating in respect of the Climate Change Committee, what do you think the Government should be doing? How should it be addressing the need for a more consistent and regular approach towards evaluation? What would you put in place? What would you advocate? It is all very well to say what should happen but what would you do to evaluate our existing policies on that?

Professor Anderson: They are not going to point us in the right direction and that is principally because they are driven by the price mechanism. The price mechanism for dealing with climate change is just one of a suite of instruments it might use and it is being overly emphasised as to its importance. The price mechanism is a perfectly reasonable route to go down if you have marginal adjustments year-on-year. If you want to reduce emissions by one per cent per year, yes, up the price of carbon, up the price of fossil fuels and you will gradually move in that direction. You will not deal with climate change but you can use the price mechanism. If you want to deal with climate change you are going to have to look at some reductions that are far greater and there are enormous equity implications from doing that, so I think you require far more of a regulatory framework. If Government is going to genuinely be committed to climate change it has to no longer be fearful of very stringent regulation and there should be no get-out clauses in this. For instance, in the legislation that is coming through on cars some time soon I think it is 130 grams per kilometre of CO₂. That is a fleet average. If a car can be made at 130 grams per kilometre, and Audi made the A2, which is a four-seater, with 94 miles per gallon at 100 grams per kilometre about seven or eight years ago, you should be selling no car above 130 grams, not as the fleet average. The regulatory framework should be really clear on this, that in miles per gallon terms no car should be allowed to be sold on a forecourt next year that does less than 50 miles per gallon, and it will be improved at five per cent every single year, year in, year out, to give a real clear market signal. That is no new technology; we do that already for some of our cars. That also affects the role model issue. The Top Gear end becomes about driving the more efficient car rather than the faster car. I think we need to have really clear regulations like that. I would have a moratorium on airport expansion, so no airport expansion until the improvement in efficiency from aviation can be matched to any growth rate. There should be no increase in emissions in aviation.

Q108 Joan Walley: You have just mentioned two things. You have mentioned greater emphasis on and use of regulation and you have mentioned the whole issue towards airports and airport capacity and airport policy, but, given that we have got the Climate Change Committee and we have got DECC, what you have just talked about in terms of trying to change the policy framework links to two different government departments, ie, BERR and the Department for Transport.

Professor Anderson: And Treasury.

Q109 Joan Walley: And Treasury. In terms of what you are saying, how would you reconcile these different government departments with the work of the Climate Change Committee and its policy framework?

Professor Anderson: I assumed that government was completely joined up nowadays so it would automatically transfer between these departments. That is what we have been told for a long time. In reality the Government is like every other part of our own lives - there are all these separate elements where there is no integrated thinking. There is lots of integrated rhetoric, and that is not just in government. I work in the university and the whole university spectrum is like that. It is set up in silos. Our own lives are like this where we do not behave rationally. It is a huge problem. I regard this not just as a government problem; it is a huge problem of our modern society - how do we integrate and think about these sets of issues and sustainability? We have to deal with that across the board of these remits. You have to have far more powerful ministries. At the moment they are little snapping dogs at the ankles of BERR and Transport and Treasury. That is not appropriate. What they are setting in train has to be fundamental in what the Treasury is thinking about and what BERR is thinking about and what Transport is thinking about, so they will have to meet with the goals that have been laid out by the Committee on Climate Change, or, I would suggest, more stringent goals. There is no sign of that occurring yet but there is if you look at places like the Welsh Assembly Government, and arguably it may be occurring in Scotland, where you see more integration. I think the UK Government is a peculiarly English government in that sense in that it maintains this level of fragmentation and hierarchy that is not immediately evident. If you talk to Jane Davidson in Wales, she is driving through all sorts of things in Wales with a peanut budget, and it also gets opposition within the Welsh Assembly Government, that we are just not prepared to do here. There are examples out there of governments even within our own boundaries that are demonstrating greater leadership on integration. I think the UK, as I say, almost a peculiarly English government, is not demonstrating that at the moment and that is another area of leadership where we should be showing that to the rest of the world, that we can actually do that, that Treasury will jump to the tune sometimes of DECC and Defra, which it certainly does not do at the moment.

Q110 Joan Walley: And in this joined-up world that we are talking about how would you make sure that all the changes and advances and greater understanding in respect of scientific awareness is then consistently and periodically factored into this non-silo operation of other government departments?

Professor Anderson: One thing that is happening at the moment, and this is my own experience; I have recently given a number of talks to DFID, is that there has been a whole range of seminars we have set up for DFID and they look to me to be really interesting dialogues. It is very much a two-way dialogue. As academics it is good for us to have some sense of what is going on in the political process. There was a two-day event and they have got some follow-ups to that. I have got some more seminars coming up with DECC, so I think those standard mechanisms can allow us to get the message across to the policy makers, but we do not get asked to go to BERR, Transport or the Treasury. We are there at DECC and Defra. I do not think there is anything particularly difficult about getting the scientific message across; I think we know how to do that, and it is the Committee on Climate Change's responsibility to do that as well. It is the idea that, once you have got the message across, what powers are there to ensure that these ministries match the requirements of what the science has shown, interpreted through the committee and the way it does that?

Q111 Joan Walley: How much would you say that that links back to whether or not there is or is not a sufficiently broad skill-set amongst the professionals and the civil servants in each of the silo departments that you have just referred to?

Professor Anderson: I have met some very good civil servants and some very good MPs, but many of them, I think, still probably struggle with some of the science. I do not know if anyone has got the graphs on this, but my guess is that there are far more people trained in the classics than there are trained in science across the Civil Service and across Parliament, all of the MPs, and the Lords for that matter. I think that is probably not particularly healthy, and I think that is a long-term issue, how you overcome that. I do not think we are going to do that overnight.

Q112 Chairman: Thank you very much. We have covered quite a lot of ground. Your characteristic trenchant views are of interest to the committee and we will be discussing them further, I am sure.

Professor Anderson: I thought they were moderate views!

Chairman: Thank you very much for coming in.

Memorandum submitted by the Met Office

 

Examination of Witnesses

Witnesses: Professor John Mitchell OBE and Dr Jason Lowe, Met Office, gave evidence.

Q113 Chairman: Good morning. Thank you for coming in. Also, I think it is very helpful that you have heard the previous evidence as well. As we go through the points we want to discuss you may wish to comment on what Professor Anderson has said. Could I start with a general question? Do you think that the targets and budgets which the Government are now presenting are actually consistent with limiting the risk of dangerous climate change?

Professor Mitchell: If I can go back a bit, I think one of the big issues is uncertainty in climate sensitivity. One can specify what the emissions are and work out what the concentrations are, but the uncertainty comes when one tries to translate that into a temperature target, and I think, in taking the approach that we have recently, rather than having single values but trying to look at a probability distribution of what that sensitivity is, is a major step forward. It is the first attempt at this and the science may change, but I think it makes a lot more sense than what people have tried to do in the past, taking a single scenario.

Q114 Chairman: Using that approach.

Professor Mitchell: I certainly approve of that approach.

Q115 Chairman: Let us try and look at that now. If we take the scenarios about a range of concentrations and what that means in terms of global average temperature rise, do you think at the moment, when we are talking about aiming for a 50 per cent risk of exceeding two degrees centigrade, that is consistent with the level of concentrations we are likely to achieve given the emissions pathway?

Professor Mitchell: The whole point of having probability distribution is to allow you to look at risk, so it is more a policy issue what level of risk you take, but from the science point of view what we are trying to do is quantify that level of risk to the degree we can given our current understanding of climate, and I think we are satisfied, given the understanding we have at present, that we have specified those levels as well as we can.

Dr Lowe: I would like to add something to that. The risk estimate comes from our uncertainty in this particular quantity of climate sensitivity, but there are different estimates of the uncertainty, so, if you like, there is uncertainty on the uncertainty. What has been done in the Climate Change Committee work is that they have taken the 50:50 value from one particular climate sensitivity distribution and the particular distribution they have chosen is the higher distribution. So they have actually taken a precautionary approach. I prefer to think of the 50:50 as choosing a value from the centre of the distribution, i.e. half the models are above it, have are below it. So it is operating in a region where we have more faith in those models but it has this precautionary point of view that we have taken, this particular estimate of uncertainty.

Q116 Chairman: We are getting into a lot of unknown unknowns! If we wanted to significantly reduce the risk of exceeding two degrees, which is said to be 50:50 - that is the present level - does that imply aiming for a much lower concentration of greenhouse gas in the atmosphere?

Professor Mitchell: Yes, that is the whole ethos behind the approach, that it allows you to say, "Well, we are going to take a 50:50 chance", or, "We think, if we are going to take a precaution principle, we are going to cover a much lower risk of exceeding that value.

Q117 Chairman: Okay. So that is the scientific, reasonably confident conclusion. Is it possible to quantify how much effort we are going to have to make if we want to get that 50 per cent risk of exceeding two degrees to increase.

Professor Mitchell: To reduce the uncertain uncertainty?

Q118 Chairman: Well, yes. Suppose we were to say we only want ten per cent risk of exceeding two degrees? Can we then translate that into a scientific objective as well in terms of greenhouse gas concentration?

Professor Mitchell: I think, in general, as one goes to lower levels of risk, just from a statistical point of view, it becomes more difficult to pinpoint that accurately. I think we actually have looked at one per cent risk, but the uncertainty in the tail of the distribution is much greater than in the centre, and that is one reason for emphasising the centre. In the same way, in the recent adaptation scenarios that have been released, we have not gone beyond ten per cent, because you are starting to get larger uncertainties once you get down to that level.

Q119 Chairman: Looking at the issue of carbon budgeting, which is what is actually scheduled as the aim of this inquiry, we have got budgets set as far as 2022 now and in a couple of years' time the next period up to 2027 will also be set. That is 17, 18 years. Do we need to consider setting budgets any further in advance than that, or is that sufficient?

Professor Mitchell: I think, from a science point of view, if you know where you want to get to, then you probably want to look out further so that you can check that what you are doing you can do continuously. If you are just setting targets over the next 15 years but you are not sure where you are going after that, then I think you are leaving open the case where you may come into a situation where you cannot achieve your longer-term aim. The second comment I would make is that, of course, science does change, and one does need to be aware of being able to update the science as appropriate, and I think that needs to be incorporated in whatever legislation you are putting in place.

Dr Lowe: It is probably worth adding there is a halfway house where, yes, it would be great to specify the entire trajectory of emissions, and that is what we do with the modelling work, but a halfway house is that you specify the emissions for some time into the future, perhaps up to 2030 or 2050, but with that you also have a cumulative total, so a much longer-term time horizon as well, because of the long response times in the system.

Q120 Chairman: One of the powerful points made earlier was that we are investing in infrastructure whose lifespan will go well beyond 2027. When we build a new aircraft now the expectation is that it will be used for probably 30 years. The same might be true of a power station when we have got no date for carbon capture and storage. So we are making decisions which will directly affect emissions well into the 2030s, which would seem to strengthen the case for having budgets which go with that.

Professor Mitchell: That is certainly the case for the longer-term infrastructure as well.

Q121 Colin Challen: I wonder if you have a view on what kinds of developments in the science might take place which would trigger, perhaps, a review of the budgets that the Climate Change Committee has set and whether there has been anything in recent months which, in your view, could actually count as such an important change: because, I think, correct me if I am wrong, we have been told that the Independent Climate Change Committee has based the bulk of its science on the IPCC Fourth Assessment of the science which is a few years old and has been through a peer review process, and so on.

Professor Mitchell: I think it could put things in perspective. I have been involved in this science for about 35 years and in 1978 one of the National Academy of Science committees came out with a range of about one and a half to four and a half degrees for doubling CO₂, and that has not changed that much over that period. There has been a lot of oscillation within it. The second comment I would make is that science progresses regularly; so trying to predict surprises can be difficult. Having said that, I think the assessment made in 2007 was a good and solid assessment. I think the recent meeting in Copenhagen tended to emphasise some of the more speculative aspects of climate change, including the ice sheets and perhaps methane clathrates, and those probably are issues for the longer term and, of course, for mitigation in this committee, but I think one always has a problem as a scientist between giving what is the well-established view but being aware of possible surprises in the future. There were a couple of issues that came up in Copenhagen. One was the rate of rise of sea level - have we underestimated the rate of melting ice sheets - the other is probably what happens to methane which is locked in the tundra, and, again, that is something which is not going to be an issue until you get to the larger increases in temperature.

Q122 Colin Challen: You heard the evidence from our previous witness (which, I have to say, I tend to agree with) that, like engineers, we should perhaps over engineer our structure. If we are going to build a bridge, you try and build it, these days, to withstand totally unlikely events so that it is going to last and do the job. Should not science also be doing that, given that we are discovering all the time and the discoveries tend to go in the wrong direction? I am thinking about things like ocean acidification, and so on, much better understood now than maybe a few years ago, but a lot more to learn, and that applies to a great many of these areas. So should we actually not just say we will fix ourselves on a central band or the more optimistic opinion but to over engineer?

Professor Mitchell: There is a cost that comes with that, and, I think, again coming back to looking at the more populist risk-based approach, that is where the science is going. Take something like the Thames Barrier. You are between two extremes. You do not want to under engineer that and then have a catastrophic flooding event; on the other hand you do not want to over engineering it and spend a huge amount of money for a risk that is very small; and that will depend on the particular case that you are looking at. So the level of risk is different for different applications, and that is why we have taken that approach. In terms of taking a precautionary principle, I think that is very much a political decision and the role as a scientist is to provide the evidence which supports that in the most faithful way possible.

Q123 Colin Challen: I was at the Copenhagen Conference earlier this year. The impression I got was that the error band, if you like, on the models has been consistently optimistic and that the empirical data that is now coming in, in droves, points to a worse picture. Do you think that the Climate Change Committee has the flexibility to handle this and to make recommendations in a timely fashion?

Professor Mitchell: Could I clarify what you mean by "optimistic"?

Q124 Colin Challen: In terms of?

Professor Mitchell: The modelling.

Q125 Colin Challen: If we look at the ice sheet data that has been observed, the trend there has been significantly worse than was predicted. This is going back just a few years, but, all the same, you can see the trend is below the worst model, if you like. I am not a scientist; I am just trying to express the graphs that I have seen based on the empirical data versus the models.

Professor Mitchell: I think one has to be careful looking at observations, because they include both the longer-term trends due to greenhouse gases but also short-term variability. In your example, I am not sure whether you are referring to land ice or sea ice.

Q126 Colin Challen: Sea ice.

Professor Mitchell: Certainly there has been a very marked decrease in sea ice. We know year to year and over a period of several years that can vary a lot, and we have to be careful we do not base policy on what turns out to be a short-term natural event which exaggerates the rate of climate change, but, similarly, not to underestimate the effects due to short-term effects which reduce it. So part of the science is to try and clarify whether that is due to natural variability, and that is one of the things that the probabilistic approach can take into account, because we can look at the observations, we can look at natural variability, we can factor that into the estimates that we make for the future. Again, I think it emphasises the importance of going from single model estimates to looking at what the range of variability is, what the sources of uncertainty are, and it also leads you then into how you much focus efforts to reduce those uncertainties.

Dr Lowe: Can I add to that? With sea ice in particular, yes, there has been a lot of attention to whether the models can actually reproduce the recent rapid declines. What we found in a version of our own model is that, when you include natural variability and you put that on top of the climate signal, then you can get year to year variations as large as some of the recent ones we have seen. Can I just bring in land ice, because there was so much focus on that at Copenhagen? The emphasis there was on evidence that suggested further acceleration of the contribution of land ice to sea level rise, but emerging in the literature there are other counter-arguments. For instance, there was a talk at the AGU late last year that presented evidence of a slow down of some of the outlet glaciers and some modelling work was published in Nature Geoscience on that. So, as part of taking a balanced view, we look at both the studies that are suggesting acceleration and the studies that suggest deceleration.

Q127 Colin Challen: Just to be clear, would you say that the evidence generally points to the models being pretty much correct within their range of uncertainties?

Professor Mitchell: I am not aware of anything which shows a large disagreement. The UKCP scenarios were produced taking a wide range of models but then looking at observational constraints, how well they simulated certain aspects of the present climate, how well they simulated recent trends, to weed out those models which were less credible than the others, and certainly the results we got from that are very consistent with IPCC 2007. There is a dilemma, in that do you, when some new science comes in, latch on to it immediately with meetings like Copenhagen, or do you allow a longer period to assess the science, to weed out things which have not been thought through properly? It is a real dilemma. One of the issues with the IPCC is that it is such a long process that it can leave things out that have happened in the last two or three years.

Q128 Colin Challen: Should the Climate Change Committee that we have set up (and I think the UK is recognised as being a leader in climate change science) have a shorter timescale for reviewing these things than relying on the IPCC's four-year timescale?

Professor Mitchell: I think, in terms of the Climate Change Committee, it is obviously sensible to take into account the latest information. I think they would need to do so in terms of the background of the IPCC assessments but looking carefully at any changes from that, perhaps investigating that and, coming back to Professor Anderson's comment, looking at the science and making sure actually it does stand up to scrutiny and it is not just a single paper which is based on perhaps some short-term evidence.

Dr Lowe: We also have a new project that is funded by DECC and Defra called the AVOID. It used to be Avoiding Dangerous Climate Change but it has been shortened. The entire purpose of that project is to make sure that the mitigation science pulls through to government. So it is in the process of producing a set of scenarios that build on those of the Climate Change Committee, and it is not just a single institute study, it involves the Met Office, the Grantham Institute, the Tyndall Centre, the Walker Institute. So the idea is that we pull through this science on a more rapid basis, and we do have regular contact with staff from the Climate Change Committee.

Q129 Joan Walley: I am not a scientist, so I am getting a little bit confused with all of this modelling and the way in which the modelling is shaping the policy that comes out of it. Previously we had Lord Turner, in his evidence to committee, saying that climate models incorporate carbon cycle feedbacks, and then it turns out that there is a distinction between feedbacks. Then there is the concern about the Global Commons Institute saying that you have got coupled and uncoupled models. I am just wondering if you can explain to me, in layman's language, the way in which the Climate Change Committee has taken its evidence in this coupling, whether or not it has taken all the concerns on board that it should have done and whether or not there is not a sort of faster race where not the whole thing is based on what is actually happening.

Professor Mitchell: In terms of the modelling, I think the first thing to make clear is that it is based on physical, biological and chemical processes which we understand to a greater or lesser extent. So it is not like economic modelling, where you have various empirical models, it is actually based on the laws of physics. In terms of what you include in the model, the earlier models did not include the carbon cycle. Those processes have now been added, so that the carbon concentration depends on how the biosphere changes, how the ocean carbon cycle changes in terms of temperature, circulation and so forth. In adding feedbacks, we do not explicitly add a feedback: we will add the processes that we understand to be important, and, when those work together, the feedback will come from that, so we do not prescribe feedbacks specifically. When we say things are coupled, it means that all those processes are combined together and work together, rather than running one model and then running another model. I am trying to remember the question.

Q130 Joan Walley: The concern that I have is that, in evidence that we have had from the Global Commons Institute from Aubrey Mayer, he has pointed out that the IPCC has specifically said the omission feedbacks from models was an issue and that the real question is whether or not you have coupled or uncoupled feedbacks. Is that something which you have taken into account?

Professor Mitchell: The models will take into account all the feedbacks we are aware of that we think are important, then we can quantify that we understand, and to that extent the Climate Change Committee has obviously done that. Science being science, we uncover new feedbacks and there is a delay in being able to incorporate those in the complex models. One can use simple models to get, if you like, a fast-track estimate of what the effect would be, but one would have to refer to the more complex models to make sure that when you add that additional feedback you are actually taking into account all the processes that are important.

Q131 Joan Walley: Two things on that. The first thing is that Aubrey Meyer said that the models used by the Committee on Climate Change were uncoupled. Therefore, his recommendation was that, because they were uncoupled, they were not suitable. Would you agree with that?

Dr Lowe: I am going to take that one. I had a look at the submission from the Global Commons Institute last night and the figure I think you refer to comes from IPCC in chapter ten and, in this context, "uncoupled" refers to whether temperature feeds back onto the carbon cycle, so where the temperature and rainfall can affect how trees take up carbon, and it has a very particular meaning. The curve in question, basically you run the model without this effective climate back on to trees and the biosphere and you get one number, you run it again with this effect, the coupled version, you get a different number and, if you have got the same emissions going in, the coupled version leads to typically a higher concentration because you are increasing the emissions that come back from the biosphere. The runs that the Climate Change Committee used do include those feedbacks, so in that definition they were described as coupled. The precise values we use to work out the magnitude of the coupling comes from elsewhere in IPCC and from a study referred to as a C4 MIB study, which to date is the most comprehensive analysis of that particular type of feedback onto the carbon cycle.

Q132 Joan Walley: In your written evidence that you have given to us (and, as I say, I am not a scientist, so this is all very difficult for me) you say that the models that were used by the Committee on Climate Change were suitable, but you also go on to say that you would call for further simulations using the Earth System Model. Does that mean that you are not accepting that the data and the assumptions that were taken by the Climate Change Committee were adequate and sufficient, or are you saying that far more needs to be done on this modelling, taking into account coupled and uncoupled versions? If so, can you say why this is necessary, and what would be the costs of doing that and what would be the benefits of doing that work?

Professor Mitchell: I think one of the reasons is that the Earth System Models, which take into account all these feedbacks - they take into account the weather, the oceans, the forests, the effect of the carbon cycle on the oceans - are expensive to run. So what we do is take those models and we run them over a number of scenarios and then we can use that to produce simple models, much in the way that Professor Anderson has used - taking the global models and simplifying them. You can then do a lot of investigations very cheaply.

Q133 Joan Walley: I thought our earlier witness this morning, Professor Anderson, was warning us, that because, for example, food, deforestation, aviation and shipping had not been taken fully into account, that was going to open up massive short-comings in the way in which the whole premise of what was going forward was taking place.

Professor Mitchell: I think that refers to how you control emissions. In the modelling, we take the human induced emissions, and those are prescribed. So I think that was referring more to how you reduce emissions rather than, given an emissions scenario, how then you include that in the model.

Q134 Joan Walley: But the modelling has, somehow or another, to be connected to where the emissions are, does it not, at some stage?

Professor Mitchell: That is more the socio-economic modelling, which the Met Office is not involved with. We will start with a set of emissions which will be tied to some kind of socio-economic scenario, make certain assumptions about aviation, and so forth. As far as the atmosphere is concerned, it does not really matter where the carbon comes from, it gets well mixed, and hence it is not relevant to the science of working out what the climate impacts are given a set of emissions.

Q135 Joan Walley: So why is it necessary to do this Earth System Model?

Professor Mitchell: To know what the effect of carbon dioxide is on climate, taking into account all the different interactions between the atmosphere, the ocean, how the carbon cycle itself responds both to changes in climate and to changes in carbon dioxide, because it will respond to the induced changes of carbon dioxide. So it is to make sure you have got a holistic picture of the whole system of climate and the carbon cycle. To do that properly you need a full three-dimensional model, and, as I say, that is too expensive to run a lot of scenarios.

Q136 Joan Walley: How do you mean too expensive?

Professor Mitchell: In terms of computer time. These things are enormously expensive in terms of computer time, and that is probably one of the main limitations.

Q137 Joan Walley: Are you saying there is not the capacity to actually do this work?

Professor Mitchell: There is not the capacity to do, in detail, all scenarios.

Q138 Joan Walley: If it is needed, why can we not be doing it?

Professor Mitchell: To a first approximation you can take the complex model and look at the results and simplify those to get broad relationships between emissions, temperature and carbon dioxide, and that is what we have done. When we look at those results, we will then come back and check any key results with the global model, but we cannot explore the whole range.

Dr Lowe: The type of models we have used, the simple models, they are simple Earth System Models and they are good at reproducing some of the features of the more complex three-dimensional models that John refers to. So they are good at producing global average temperature, and we have tested them by comparing them with the more complex models over a range of different scenarios. At the moment there are fewer simulations of the type of scenarios we are talking about here, with very strong mitigation. I think part of the suggestion is that it would be nice to do some further testing with this particular type of scenario. As it happens, we have now done some of that very recently and we find a simple model does have some skill even for that type of scenario. The second point, though, is that the complex models do give you something extra. They tell to you what is happening regionally so you can actually go down and look at the process within the model regionally and say, "Is that realistic?"; whereas with the global model you can only look on a global average; you are averaging out some of the information. Also, because it has this more elaborate way of representing processes, if there are any surprises within the system, any local more rapid changes, then you will see them within the three-dimensional model. So we would not run this more elaborate model for the 729 model variants that we ran for every scenario that was used in the Climate Change Committee, what we would suggest doing is maybe picking one, two or three of those across the temperature range, almost as a check, to see what is happening regionally.

Q139 Joan Walley: Is that something you are going to be doing automatically or is that something which somebody somewhere needs to be showing leadership on and pushing for?

Dr Lowe: That is something the AVOID project has in mind doing.

Q140 Joan Walley: So it is doing it anyway.

Dr Lowe: We are doing it anyway.

Q141 Joan Walley: To the extent that you need it to be done. It is doing it fully, 100 per cent?

Dr Lowe: It is doing a subset of three-dimensional model runs. I think it is a matter of trying to debate how many you would really want to do.

Q142 Joan Walley: How many would you really want? How many would it be nice to have and how many is it necessary to have?

Professor Mitchell: It depends on the degree to which you want to take out your results. The assumption is that the simple model does a reasonably good job, but, as Jason has alluded, there may be certain regimes where, either locally or even globally, you do see some marked responses, some extreme responses, which are unexpected. So it is a question of how certain you want to be of those results.

Q143 Joan Walley: So that I am clear, is that actually incorporated in this AVOID project that you referred to that, is it, Defra are doing?

Dr Lowe: Defra and DECC are funding this.

Q144 Joan Walley: I just need to know, yes or no, are they covering it in full or does some pressure need to come from somewhere to make sure that it happens?

Dr Lowe: Some of it has already happened (some of it has now been done); some more of it is planned on the work plan, on the timeline of AVOID already.

Q145 Joan Walley: Is that exactly what you want to happen, or are you asking for more than is currently funded or possible?

Professor Mitchell: I think there is always room for improvement. It is not just on the litigation side but also on the adaptation side. In terms of the, modelling, as Jason alluded to, changes regionally in the carbon cycle add up to the global total. Therefore, the more accurately you can do regional climate change, the more accurately you can look at the carbon budgets as well as the climate change to which we are adapting. One of the issues that we have had with the UKCP scenarios is that we are aware that, for example, the modelling of storm tracks, which are particularly important for climate, is poor in models. So one of the things we would like to do is to do that better. For that we need high resolution, for that we need more computing, and that is something that the Met Office is already engaged in working towards. The limitations, perhaps not so for mitigation, except in terms of the scope of things you can cover, but for adaptation being able to model in more detail is important.

Q146 Mr Chaytor: To what extent do you think the Committee on Climate Change has taken on board the scientific evidence and translated it directly into appropriate policy recommendations, or do you think the committee is being too pragmatic in terms of only recommending what it judges to be politically feasible?

Professor Mitchell: What we have done at the Climate Change Committee is they have said these are the scenarios we would like you to look at. We have run those scenarios to see what the effect on climate is and what the effect on the carbon cycle is. Jason probably has had more contact with that. That is work he has been involved in. I have also had contact on the adaptation side, where I have explained what we have done for the UKCP scenarios, so I know they are listening to what the science is and taking it into account. In terms of mitigation scenarios, you have had direct contact with the Climate Change Committee.

Dr Lowe: Yes. This has been quite a long process. We have had numerous discussions on the various uncertainties. So several of the topics like feedbacks that have come up today, there have been numerous discussions behind those. These, again, have not just involved one or two people, they have involved multiple experts coming in. In that way I think there has been a fairly good examination of the available science, that is the available science that is coming through AR4, but also the post AR4 science. For instance, there were staff from the committee at the Copenhagen Climate Change Conference to see what new was coming out of that. That seems pretty current in terms of pulling in new information.

Q147 Mr Chaytor: But in terms of the committee's reports, the committee's recommendations over targets and budgets, do you think that what we now have in respect of targets and budgets accurately reflects the significance of the scientific recommendations, or do you think there is some mediation and some compromise there?

Dr Lowe: When I look in a report I can see how the budget numbers trace through to the climate simulations that we ran. I am not sure if that answers your question directly.

Q148 Mr Chaytor: It answers it indirectly. You mentioned the uncertainties. There are uncertainties over CO₂ emissions but also uncertainties over non CO₂ emissions. Could you say a bit more about that?

Dr Lowe: Yes and no. No, in the sense that for us those emissions are the input, if you like, and then we combine the uncertainty on those scenarios with the climate modelling uncertainty. Yes, in the sense that in both the Climate Change Committee work, and now extending that in the on-going projects, we run a range of different scenarios. These have a range of different CO₂ and non CO₂ gases. One particular uncertainty, in the form of atmospheric aerosols, we have looked at in a lot of detail to see how that moves the temperature probability results around, for instance, so it is in there.

Q149 Mr Chaytor: In terms of what is missing, a lot of the science has progressed rapidly in recent years, and who knows what new insights are going to be developed shortly, but what is the most important missing areas of data now? What knowledge do you need most urgently to increase the level of certainty about your predictions?

Professor Mitchell: There is a lot of uncertainty but of the two main areas, one is probably cloud climate feedbacks. Clouds can either cool the climate, because they reflect the solar radiation back to space, but they also have a very strong greenhouse effect. So very small changes in cloudiness can have quite an effect on the earth's budget and, of course, with a warmer and moister atmosphere, it changes the distribution of clouds and models struggle to agree on what those changes are: so that is one of the biggest sources. We have been looking at different models to understand the key processes in determining that uncertainty, what observations we have to make to increase the physical understanding, to reduce the uncertainty, particularly through things like satellite, through aircraft measurements, and so forth. So that is the one big area. The other area is the carbon cycle, which is relatively new in terms of our system modelling. Jason mentioned the C4 MIB, which is a carbon cycle climate change inter-comparison project. Again, looking at the models, trying to understand why they differ, then relating that to our understanding of the real system and making the measurements that we need to improve it. In terms of the carbon cycle, because it is newer, I think in some ways there is more ground for progress. We know from weather-forecasting the problem of improving cloud simulations is very difficult, but, on the other hand, I have been involved in this 20 or 30 years and we have not reduced cloud uncertainty, but I think we are now getting to the stage where people really are concentrating on the processes rather than just running new simulations for scenarios, and I think there is a need for science to concentrate on that if we are not going to go on with this level of uncertainty.

Q150 Mr Chaytor: Are we dealing here with things on such a gigantic scale and over such a long time-frame that scientists really will have to accept that there will always be massive uncertainties? If we are trying to make scientific assessments to inform public policy in 50 years' time, has this ever been done before? Can you think of analogies of previous projections over such a long period of time?

Professor Mitchell: Not over that period of time, but I think you are right. What we tend to do is prioritise those things where we know we can make a difference quickly, but, on the other hand, if we do not start soon looking at some of these long-term uncertainties, we certainly will not reduce them. To some extent it is an act of faith. With science being science there are some things which we will be able to develop and some things which we will not, but we certainly need to maintain that effort, and I think there is a danger, if we do not do that, we could be five, ten years down the road and find we actually cannot say more than we can at present. So it is maintaining the longer term research to reduce those uncertainties at the same time as making specific efforts to answer the sort of questions that you are asking today.

Q151 Chairman: Your memo to us suggested that the estimate that the Committee on Climate Change have made on the probability of staying below two degrees centigrade represented a precautionary approach. Can you explain exactly what you mean by the phrase "precautionary approach" in this context?

Dr Lowe: That is a much easier one to do with a diagram actually, so we may need to supply that afterwards, but I will have a go first. It comes back to this point that one of the key uncertainties is climate sensitivity, and there are several different estimates of that measure of uncertainty. The Hadley Centre produces one, other climate institutes produce another. There are of the order of 15 of these now, but maybe more, because more are cropping up, and these uncertainty estimates are made in differing ways. If you were to sit down, the simplest thing would be to say, if we are interested in relating the stabilisation concentration of CO₂ that gives a 50 per cent chance of going over two degrees, we would come out with a different number for that CO₂ concentration depending on which of those uncertainty distributions we go for, and what we find is that the Murphy et all distribution that we used in this work tends to give, if you like, the lower chance of staying below two, or it suggests that you need a lower concentration than some of the other versions. Again, this would be much easier with a diagram. I think perhaps a diagram with a couple of arrows may clear up the point very simply.

Q152 Chairman: In that case we will wait for the diagram. There is quite a significant difference between the Committee on Climate Change's work and the work done by Professor Anderson. How do you explain that?

Dr Lowe: Firstly, it is a very different method. We are starting with the emissions: from that we are working forward, calculating the concentration of greenhouse gases, and from that we are calculating the temperature rise. Professor Anderson is working the other way: he is looking at an existing model study that has levelled out CO₂ concentrations at 450 ppm, CO₂ only. That has given him, if you like, a lump of carbon in total. He has then said, okay, if this is our allowable lump that leads to 450, some of that is used up already with what has come to the present day, some of that will be used up with non CO₂ gases and what we have got left we will divide up over the years with a particular shape. So it is working backwards from the target. One thing it assumes is that you can take this lump of CO_2, this cumulative CO₂ amount, and apply it as a cumulative CO₂ equivalent; so you can include the other gases in that. We are not as convinced you can do it in that way, and so to test that Professor Anderson has been kind enough to supply his emissions, and one thing we have been doing very recently is running them forward through the method we use. When we do that we find, if we take a particular case which peaked in 2015, I believe, and run that forward, because of our more precautionary climate sensitivity value, that gives a chance of exceeding two degrees of the order of 65 per cent rather than the 50:50. So it is worse, because we are now running it with our precautionary estimate, but then, when we put in aerosols, we find that pulls the probability down again. So it pulls it down from 65 per cent to a little under 40 per cent. I think the main point there is that it is a different set of assumptions but it is moving the numbers around in terms of probability by several per cent. What I found looking at additional studies - because published recently there was also work by Meinshausen et al, by Miles Allen et al and by Martin Parry et al - is that the studies tend to become quite close in terms of the temperature level they approach within point two, point three degrees, but they disagree more on the probability numbers, and in some ways that suggests that the central estimate of the 50:50 temperature is actually a more robust measure to use when comparing different techniques. We would be more than happy to sit down and take the inter-comparison with Professor Anderson further and really tease out what the difference is between the two studies.

Q153 Chairman: I am sure that will be interesting. Are there any other questions? No. Is there any other burning issue that we should have raised with you but we have failed to do so?

Professor Mitchell: No, I do not think so, thank you.

Chairman: No. Then thank you very much for your time. We are grateful to you.