To be published as HC 1739-ii

House of COMMONS



Environmental Audit Committee

Protecting the Arctic

Tuesday 21 February 2012

Professor Tim Lenton, Professor Peter Wadhams and John Nissen

Evidence heard in Public Questions 15-50



This is a corrected transcript of evidence taken in public and reported to the House. The transcript has been placed on the internet on the authority of the Committee, and copies have been made available by the Vote Office for the use of Members and others.


The transcript is an approved formal record of these proceedings. It will be printed in due course.

Oral Evidence

Taken before the Environmental Audit Committee

on Tuesday 21 February 2012

Members present:

Joan Walley (Chair)

Peter Aldous

Katy Clark

Zac Goldsmith

Mark Lazarowicz

Caroline Lucas

Sheryll Murray

Paul Uppal

Dr Alan Whitehead


Examination of Witnesses

Witnesses: Professor Tim Lenton, Professor of Earth System Science, University of Exeter, Professor PeterWadhams, Professor of Ocean Physics, University of Cambridge, and John Nissen, Chair, Arctic Methane Emergency Working Group, gave evidence.

Q15 Chair: I welcome you all to the Committee. I think we are all looking forward to getting our inquiry on the Arctic properly under way. I understand that you would each like to make a short statement to the Committee, which I think might help us get some kind of perspective on the different issues. Perhaps, Professor Lenton, if we could start with you that would be very helpful.

Professor Lenton: Thanks, Joan. The first thing to say, I guess, is that I think the Arctic might be the first region of the planet on a largish scale that may be experiencing dangerous climate change. The United Nations Framework Convention on Climate Change is all about trying to prevent dangerous anthropogenic interference in the climate system. We have spent a couple of decades debating how to define "dangerous change", but the Intergovernmental Panel on Climate Change actually has what it calls five reasons for concern, which are all fulfilled, I would say, in the Arctic region. These are risks to unique and threatened systems, in this case ecosystems and you could say Inuit cultures; risks of extreme weather events, which I could elaborate on but are increasing; an uneven distribution of the impacts of climate change there; aggregate damages becoming quite significant; and the thing I am particularly working on is what IPCC call "risk of large-scale discontinuities", which in my language is climate tipping points.

Just to highlight a few of those, I think the thing that is changing most abruptly and most surprisingly recently has been the Arctic sea ice cover. We are certainly trying to do some work that might suggest it has already passed some kind of tipping point. Nearby, if you like, the Greenland Ice Sheet, because it holds ultimately 7 metres of global sea level rise and is estimated to have a potentially near threshold in terms of global warming, possibly requiring only one or two more degrees of warming before you commit it to an irreversible retreat, is clearly a big concern.

The third tipping element, as I call it, would be thinking about the Atlantic overturning circulation and its regions of deepwater formation on either side of Greenland. Recent work is suggesting our models have been biased in a stable direction for that system and that we might revisit the possibility that there are multiple states for the Atlantic circulation and the threshold may be closer than the last generation of models suggested.

Then, on the land surface, we are seeing dieback of the boreal forests, certainly in parts of Canada, quite strikingly. This can be tied back to a warming signal and the spread and flourishing of bark beetles that are essentially killing the trees. In terms of the permafrost, I think there is one particular region in Siberia-they call it locally Yedoma-where you have very rich frozen reservoirs of carbon. Once they start melting and bugs start eating the carbon, this actually releases heat just like any metabolic reaction and that could trigger further melting. You could potentially see some irreversible loss of the carbon in that particular region.

Those are quite physical and ecological things in the climate. I would also say we have been doing some work thinking about the possibility of tipping points from the perspective of societies in a region as well, and that is in this special issue of the journal AMBIO that I just helped edit. I want to say a word about what the causes are, then, if there is dangerous change. What do we know about what is causing it in the Arctic? Then perhaps the most unusual message there-it is not clearly dominated by carbon dioxide, the warming signals so far. There is a strong contribution from methane and other greenhouse gas and low-level or tropospheric ozone that is produced related to the methane emissions. There is a contribution from a decline in cooling sulphate aerosols that we used to pollute the lower atmosphere with and we have been busy cleaning up. That loss of the cooling aerosols, being quite significant, contributed to Arctic warming, and so has the addition of more soot, basically, which we call black carbon aerosols. You can imagine when black particles land on the snow and ice they can accelerate melting, essentially.

It is an interesting story there. It is what we call short-lived forcing agents or warming agents that are playing a disproportionate role, but the good news is those are ones that can be mitigated more rapidly. You can have an impact on their concentrations and their effects much more quickly than you can by reducing carbon dioxide emissions. I would say they are the obvious thing to think about and to tackle in terms of mitigation.

My final word is just on the idea of early warning for these abrupt changes. Maybe you would say it is a little late now, but in my group we are working quite hard on; are there generic early warning signals for abrupt climate changes? We are using the Arctic sea ice as a test case. We have found some evidence that we have seen a switch from what used to be just the normal mean seasonal cycle of sea ice variability. We think since 2007 we have seen a second lower ice cover state, and each of the last five summers are the five lowest on record. We have seen the amplitude of the seasonal cycle of sea ice variability step up since 2007. You can view that perhaps as passing some kind of tipping point or threshold.

If you wanted to do real early warning for this suite of changes in the Arctic, you have a big problem that there is poor monitoring or sparse monitoring, especially on land and more broadly of ecosystems, including marine ones. Sea ice is easy; it is done relatively more easily, although imperfectly. We have some information from the satellites, and I am sure Peter can talk more about what we can see from underneath. That is all I wanted to say.

Q16 Chair: Thank you very much for keeping to the time limit. I will move on, if I may, to Peter Wadhams. Thank you, and your colleague as well, for coming along. Are you absolutely in agreement or are there lines of disagreement? It would be just useful to have your introductory contribution, please.

Professor Wadhams: No, I agree with everything that Tim said. Perhaps I can just expand a bit on some of the aspects that-

Mark Lazarowicz: You do agree with what he says?

Professor Wadhams: Yes, I do. I would like to expand on some of the aspects that he has mentioned, especially in relation to sea ice retreat. This is probably the feature of the earth’s surface that is most readily observable as changing, because in the summer now there is such a large area of open water that satellite pictures of the earth show it as blue at the top end, whereas in the past it was always white all the year round. The retreat of sea ice in summer from its winter maximum always used to be quite modest. There would be a narrow slot around the north of Canada and Russia, giving a Northern Sea Route and a Northwest Passage that you could get through, if you were lucky, with a big icebreaker. Today, however, the summer sea ice has retreated to the point where it forms only a limited mass in the middle of the Arctic Ocean with a lot of open water all the way around it. This is already having big impacts.

First of all, we can map the retreat quite easily from satellites because most satellites can see the difference between ice and open water. The thinning of the sea ice, however, is a much more difficult aspect to measure because you cannot easily observe that from satellites. We have been able to measure it for the last 40 years from British submarines, and also it has been measured from American submarines, so I would really like to pay tribute to the Ministry of Defence here for allowing scientists to go on board nuclear submarines and use them at every opportunity. Each time that a submarine goes to the Arctic, we go along and collect ice thickness data. This has been going on for 40 years and it is what has enabled us to spot the thinning of the ice. In fact, it was 20 years ago that we first detected from 1970s data versus 1980s data that the ice had thinned by about 15%. Now, looking at the latest data, it has thinned by more than 40%, about 45%. That is perhaps even more serious than the shrinkage so far, because what we have now in the Arctic sea ice cover is a cap over the top end of the earth that is shrinking slowly but thinning rapidly. The next stage will be a collapse, where the winter growth is more than offset by the summer melt. If we look at the volume of ice that is present in the summer, the trend is so rapidly downwards that this collapse might happen within three or four years. There is a range of predictions about how long it will take, but if we simply extrapolate from quantities that we can measure-the fact that we can measure thickness as well as area-the volume trend will result in the summer ice substantially disappearing very soon. Of course, there will always be sea ice in the winter, but it will be thinner sea ice because the ice that disappears in the summer will have to re-grow in the winter but it will all be less than one year old, called first-year ice. This ice is easy to get through with a ship and is not really a big obstacle to navigation. The way the Antarctic is now is the way that the Arctic will be in the future, a seasonal ice cover.

Q17 Chair: Is that really as catastrophic and doom-ridden as your objective evidence suggests?

Professor Wadhams: Well, it has good and bad aspects. The good, I suppose, depending on how you view it, is easier access to the Arctic for offshore drilling and transport across the Arctic. It will be possible to have trans-Arctic shipping, not even going through the Northern Sea Route or the Northwest Passage. It will be straight across the North Pole, so that will really reduce the distances, at least in summer, between Europe and the Far East.

The bad are some of the implications that Tim has mentioned. One is that the retreat of the summer sea ice from around Greenland warms up Greenland and means that the Greenland Ice Sheet melts more rapidly. That is already making a significant contribution to global sea level rise. The contribution now is about as great as all the rest of the retreating glaciers in the world put together, and that will mean that over the next century the rise in global sea levels will probably be greater than predicted by IPCC. One can expect quite a lot more than 1 metre instead of less than 70 centimetres, which was the 2007 IPCC prediction. That is one thing.

The other thing is something that John is going to talk more about, which is the fact that, when the sea ice retreats in summer from the continental shelves, the sea bed warms up over this very large shelf area. About a third of the area of the Arctic Ocean is continental shelf, mostly very shallow (about 100 metres deep). The shallow water column warms up easily if the ice cover is removed, and the warming extends to the seabed. The seabed warming means that offshore permafrost is retreating and melting-permafrost that is left over from the last Ice Age and attached to the permafrost on land. That is shrinking back because the sea bed is warming now to about 5°C in the summer, much more than in the past. This is releasing methane, and in the last couple of years there have been expeditions to the East Siberian Sea that have been showing very large emissions of methane, with huge plumes bubbling up, and the instruments detecting methane levels in the atmosphere have been showing a new rise after the methane level had flattened off in the last decade.

The fear here is that, if all of the methane trapped under offshore permafrost is released within a few years, this will give a very big boost to global warming. Released methane exerts a climatic influence over only a limited period, about seven to 10 years, but during that time it really will hit the climate in a pretty serious way if it all comes out quickly, i.e. if all that offshore permafrost melts. That is another implication of the retreat of the sea ice. It is yet another positive feedback and unfortunately the world seems to be full of such positive feedback mechanisms where one aspect of global warming leads on to something else that is even worse. We do not seem to find any negative feedbacks that buffer everything back. It is always that one change stimulates another that is even nastier. That unfortunately seems to be the experience at the moment.

Q18 Chair: Thank you. Mr Nissen, did you wish to add to your two colleagues?

John Nissen: Yes. I would just like to point out something. If you multiply the thickness of the sea ice by its area, you get a volume, and the volume decline is 75%. The projection of the best available data on one type of extrapolation gets you 2014 or 2015. If you try a different algorithm for your extrapolation, it is this year or next year.

Q19 Mark Lazarowicz: What happens this year?

John Nissen: A collapse of sea ice, indicated by extrapolation to zero on the sea ice volume trend, could happen this year. In fact, for practical purposes we are just worried about a collapse of sea ice extent down to 10% or 20% level.

Q20 Chair: Thank you. I think we wish to move on to some perhaps specific questions, so I will turn first of all to Peter Aldous.

John Nissen: Sorry, I thought I was going to have five minutes.

Chair: Oh, sorry, okay.

John Nissen: Yes, you were asking me for a response to Peter so I was putting that in because I do not have that in my-

Chair: Sorry, apologies.

John Nissen: Thank you, anyhow, for giving me the opportunity. I am presenting this evidence on behalf of a group that I founded called the Arctic Methane Emergency Group. It is a collaboration of scientists, engineers and communicators, so that includes journalists. We have a documentary in the pipeline about the Arctic emergency because we think it is extremely serious and needs to be drawn to the attention of the public.

As you have just heard from Peter here, the imminent collapse of Arctic sea ice poses a new emergency situation. We think that it threatens an irreversible transition towards abrupt and catastrophic climate change, so these positive feedbacks accelerating things are just making matters worse and worse. There is no sign of anything corrective in nature that is naturally going to come to our help, so effectively, once the sea ice has gone for any appreciable time in the year, like September, this could prove to be a point of no return because the forces are building up. There could be twice as much forcing going on if this collapse occurs, when it occurs. This is really a national or, you could say, international security alert.

From the sea ice going we have a possibility of ocean circulation changing, floods and so on, weather patterns changing, but I am addressing mainly methane. Now, some facts about the methane. Methane is the main constituent of natural gas so that is what I am talking about: natural gas. It has a fantastically potent global warming effect. The IPCC reckoned it is 72 times more than CO2 over 20 years. More recent evidence suggests it is over 100 times. The Arctic has a potential to produce a staggering amount of this methane; I have calculated it is about triple the weight of all the CO2 that we put up in the atmosphere. Because of its potency as a greenhouse gas, we only need release of 1% of the Arctic methane or the Arctic potential methane-that is about 35 billion tonnes, or gigatonnes as scientists call it-and that would triple the current rate of global warming. Then, of course, all our efforts to reduce CO2 would be small in comparison with that and all our attempts to keep to targets like 2°C would be out of the window, so we are in a real mess.

So, what is going on? It is very simple, really. The methane is contained in the ice or under the ice, and as the ice thaws the methane is released. It is very simple, the problem. Half of this Arctic methane is held in this shallow area that Peter talked about, on the continental shelf, and it all appears to be in a critical condition. The sea bed is warming and there is enough methane there-you (Tim Lenton) were considering "If it all comes out" – there is enough methane that we only need 1% of it to come out and we are in real trouble. It is difficult to see how civilisation could survive such a thing. This devastation that is possible has long been recognised. It is the sheer speed of events has taken everybody by surprise and, I may say, disbelief. A lot of people are just denying that this could possibly happen. That is a lot of people among the scientific community and the journalists and so on. But we are seeing now the clear evidence, and I have been to international conferences of geosciences to check with the scientists if it is really as bad as that, and I have not found any contradiction. There is no good news, I am afraid, apart from what we can do about it. I will come to that.

The Arctic is warming. The convention is to say it is twice the rate of global warming, but actually it is four times or more in the Arctic than it is globally. The sea-bed temperature is rising, as you (Peter Wadhams) said, by 5°C. Peter mentioned reports of expeditions to the shallow areas of the Arctic Ocean, seeing enormous plumes a kilometre across erupting from the ocean floor and the methane from those plumes is beginning to be felt in the atmosphere now. I had an email this morning saying that the latest readings from the measurements are consistent with the estimates of the Russian scientists who have been there concerning the current rate of release, which they would expect to escalate as the sea bed is warming, and with the rivers flowing into the Arctic warming as well. The thing that really struck me and caused me to convene a workshop on this whole subject was their estimate that there are 50 billion tonnes-that is 50 gigatonnes-of methane that could be released at any time from the sea bed. That is more than this 1% that I talked about. That would cause global warming to speed up by four or five times and it would overwhelm all our efforts to keep under 2°C very quickly.

Methane is a real problem and it is never really addressed. The scientists who are doing forecasting for the future and the oil companies drilling, they are never really told how dangerous it is that any methane escapes from their drilling. Drilling for either oil or gas is very dangerous-and there is a particular danger of drilling into methane hydrate because that contains very concentrated methane. It is almost explosive when it decomposes and you could set off a tsunami if you were drilling carelessly and did not have precautions. I think Peter may come back to that in talking about the oil later.

Professor Wadhams: I can say something later about that.

John Nissen: Thank you (Peter Wadhams). I am now coming to the good news. We have some excellent engineers in this country. In particular, I might like to name Professor Stephen Salter from the University of Edinburgh, who is-I am allowed to say this-a genius, I think. He has invented ways to cool the Arctic through cooling the currents flowing into the Arctic. He has a method of spraying salt water from the sea and it wafts up into clouds and it brightens clouds. He can produce enough warming but the trouble is he cannot do this immediately-he cannot get this up to scratch straight away. He has to do development of two or three years, so we have to do something in the meantime. We also have to explore other things. That is an absolute priority. We have the possibility of something dreadful happening to the sea ice this summer. We have absolutely no time to lose. Our message is, to protect the Arctic, we have to cool it and we have to do it quickly. It is so urgent that we implore you-our group (AMEG) implores you-to take this to the highest level in Government to get action. As I say, we are going public on this so the public will expect you to do something, so this is your warning.

Chair: I am sure our Committee will end up with a report and recommendations, which we will be making to Government as parliamentarians. Some of these issues we want to look at in a bit more detail, and I think one has been mentioned.

Q21 Mark Lazarowicz: Very briefly, is the time scale for ice melt that has been just outlined by Mr Nissen in general terms accepted by Professors Lenton and Wadhams? I know we can have too much to and fro, but I would be interested in very briefly knowing how you react to the urgency suggested by Mr Nissen.

Professor Lenton: I personally think it highly unlikely that we would lose the ice in the next few summers. My best guess is sometime in the 2030s, maybe 2040s roughly, there will be an ice-free summer. I personally would put quite a lot of clear blue ice-free water between my own position and John’s about how strong the feedback from the methane release is. It is not fair to say it is never really addressed. My colleagues down the road in the Hadley Centre in Exeter have permafrost in the latest state-of-the-art model being run at the moment for the next round of IPCC projections. I know they are coming to talk to you later in the month. At the moment, their best estimate is we may get 0.1°C of extra warming at the end of the century from the loss of methane from the northern high latitudes. It is a positive feedback-it is an amplifier-but it is not a very, very strong one in my personal view. I certainly would not advocate abrupt geoengineering intervention to try to counter such a threat. I think it is much more defensible to tackle some of these short-lived forcing agents.

Chair: I am sure we will get into looking at the different options in terms of solutions and the cases for and against with different evidence that we take. We just wanted to look at some specific questions, so I will move first of all again, if I may, to Peter Aldous.

Q22 Peter Aldous: I think most of the questions I was going to ask you have already covered in those fairly extensive and full introductions, which is most helpful in that you have addressed the tipping points that have come and gone and those that we face in the immediate future. What I would just like to do is go forward 20 years. If we carry on as we have been going, what does the Arctic look like in 20 years and, probably, what does Britain look like?

Professor Wadhams: Firstly, I should say I do not agree with Tim about the rate at which the summer ice is going to disappear. If you extrapolate the existing rate of retreat it might take 20 to 30 years for the ice to disappear in summer, but if you add in the effect of the thinning it is very much quicker, perhaps needing only 4 years. My feeling is that it will be so quick that, if we look 20 to 30 years ahead, we will have an open Arctic that is ice-free in summer. There may be a fringe of older ice just around the north of Greenland and Ellesmere Island. Those are places which are a kind of "Alamo" where the summer ice makes its last stand, but nearly all the rest will be blue water. This means that you will have shipping routes across the Arctic through Fram Strait (between Spitsbergen and Greenland) right across the North Pole to the Far East. You will have radically changed climate patterns around the northern hemisphere because of having so much open water present in summer with the additional evaporation that is involved as well as other factors.

Q23 Peter Aldous: How would we notice that in this country?

Professor Wadhams: Not much as far as circulation is concerned but as far as the temperature of Britain is concerned, there is a counter-intuitive factor that I was going to mention in my earlier presentation, which is that we are actually being cooled, or rather we are warming more slowly, because of the decrease in the strength in the thermohaline circulation. This is itself, weirdly enough, due to global warming. The sea ice is retreating in the Greenland Sea, and this means that the central Greenland Sea, which used to experience intensive sinking, or vertical convection, in winter, has stopped performing. It has stopped producing the "chimneys", big rotating columns, by which water was sinking from the surface to 2500 metres. Ice production was needed to enhance the density of the surface water so that it sank. This is slowing down the entire Atlantic thermohaline circulation-also called the overturning circulation-and bringing less heat in the Gulf Stream to Britain. Predictions from the European Environment Agency, which is applying the IPCC model, is that, looking further ahead, by the end of this century on a "business as usual" emissions scenario, continental Europe will have warmed by about 4°C on average. This is in the interior of Europe, and especially the Mediterranean region, which is going to become like North Africa. However, Britain and Ireland and western Norway and the Atlantic seaboard of France, because of this oceanic cooling effect, will warm by only about 2°C. It is unfair that we only get half as much warming as the others, but of course it is paid for upstream since the tropics will warm more rapidly because they are not sending as much heat up to our latitudes. Thus we can say that Britain will be warming but more slowly than the continent of Europe.

Q24 Chair: Professor Lenton, you wanted to come in, didn’t you?

Professor Lenton: Just one concrete example because I think it is already being discussed as an observed correlation, but the loss of the ice around the north of Norway and Finland in the Barents and Kara Seas in winter in particular is being correlated with so-called blocking events and the extreme cold winters in Europe. There is a mechanistic connection one can make there.

There are many factors. It is a fiendishly hard problem, blocking, and many factors can contribute to giving you persistent blocking high pressures in winter, but this is one that sea-ice loss has been tied to, for example-well, a few weeks ago it was doing it, but it was more extreme the previous winter. As we uncover the Arctic of its ice cover then the broader picture is one where you can get these blocking scenarios where essentially the jet stream spirals the planet rather than swallowing its own tail and making a ring. You already see observationally a shift in one of the centres of action of what is called the North Atlantic Oscillation, but the famous difference in pressure in between the Azores high and the Icelandic low, it is no longer so often the Icelandic low. It has moved up into that Barents/Kara Seas region. What this is broadly saying is movements of the storm tracks, movements of the jets, possible changes in blocking-those are the things we see on a seasonal time scale and can have quite big impacts.

Q25 Peter Aldous: Mr Nissen?

John Nissen: Following on from Tim, I think we are going to see enormous development of extreme weather patterns and the kind of events we have already seen with lots of snow in China and then heat waves in Siberia. This is all due to a decrease in stability as the Arctic warms relative to the rest of the planet, because the old situation was stable with a very cold Arctic and warm mid-belt of the planet. As the Arctic warms, that differential becomes smaller and then everything becomes unstable, and that is what we are seeing. That is one of the big effects.

The Arctic warming is going to be terrific. It is already about one or two degrees per decade, which is up to 10 times faster than global warming. When the sea ice goes, that Arctic warming rate is going to double again or triple or quadruple, so the temperature in the Arctic is going to go shooting up. The methane could follow that. Nobody knows how quickly the methane will escalate-the point is we are reaching a point of no return. That is the thing we have to stop. Historically, you wait until some disaster happens and then you act. For once, we have a chance of anticipating the ghastly thing and acting. It is unique. It is a unique situation we have and it is our responsibility to do something about it.

Chair: We will move on, I think.

Q26 Paul Uppal: Tim, originally you were talking about the issue of global warming in the Arctic being less driven by CO2 than elsewhere. In particular, you touched base on black carbon. I know we are going to be pursuing this line of questioning next week. I was interested in where the current research is on that, particularly specifically at the moment, and how that relates into whether that is pivotal in terms of tipping points, really. That is generally to you, but whether Peter and John would like to come in-

Professor Lenton: Black carbon becomes particularly interesting when you are talking about snow or ice melt. It is a simple idea of depositing these dark particles in the snow or ice and they absorb more sunlight, so they have a disproportionate warming effect when deposited on a snow or ice surface. They also, as black particles in the atmosphere, are having some warming effect but it is less potent.

Where the research is at at the moment is trying to tie down the sources of the soot that is getting entrained up into the Arctic. There is some clear evidence that there is quite a bit coming from China, and possibly India as well-certainly from China, the more northerly parts of China. They are somewhat related to a rush back to not entirely clean coal burning and some other sources. There has been some debate and discussion about fires in the boreal forest region, which have increased in frequency and, of course, are producing some soot in the smoke. How important is that contribution? That argument has played out with maybe not a huge contribution. We still probably lack a lot of evidence base to tie down how strong the black carbon warming effects in the Arctic region are, for example, but I think saying it is a significant contribution is reasonable. Quantitatively tying it down, there would need to be more observational work. I am more familiar with studies in the Himalayas where you have actually had direct measurements of the soot in the ice and correlated with some glacier melt. It is typically information that has come from a broader context of seeing observational links between soot deposition and ice melt that is then applied in the Arctic, but getting reliable numbers on the soot supply there and where it is coming from and how much, I think there is still some significant error bias there. We can say it looks like a significant contribution. We need a bit more research to tie that down.

Chair: Professor Wadhams, you wanted to come in as well.

Professor Wadhams: I agree with Tim-there is a lot more research to be done on this, but black carbon is reckoned to be probably the third contributor to warming in the Arctic. Carbon dioxide is the most important, methane is coming second and black carbon is third. The estimates at the moment are that it is making a contribution of about 0.3 of a watt per square metre. Everything that man is doing is contributing about two watts per square metre to the extra heat that we are receiving, and thus maybe a seventh of that is black carbon, put very crudely.

Regarding the point that John made about temperature, when I said that Britain is warming even more slowly than Europe, I should have added, of course, that the Arctic is warming much more rapidly than either of them and at a rate of at least two to three times the warming rate of lower latitudes. This has been measured over the last 50 years, so we know that the Arctic is warming faster than Europe as a whole. The impact of something like black carbon might be greater in the Arctic because of its impact on both the high albedo snow and ice and also because of the warming rate there. The further ahead we look, the greater this warming difference is between the temperature changes experienced by the rest of the earth and the temperature rises experienced in the Arctic.

Q27 Mark Lazarowicz: Can I ask something about this issue of the thermohaline circulation event, linked back to a bigger issue about tipping points and how we approach it? On the possible termination of thermohaline circulation, just to be clear, Professor Lenton, you list five major features of warming in your evidence. You mentioned something to do with the water masses off Greenland in particular. Is that what we are talking about in thermohaline circulation-

Professor Lenton: Yes, just in basic terms. You have northward flowing waters-

Mark Lazarowicz: I understand what the issue is, but that was the same point about the water masses-

Professor Lenton: You have two regions of forming deep water, North Atlantic deep water-one to the left of Greenland or the west, one to the right. To the left is the Labrador Sea, a region where this so-called deep convection has been quite temperamental and switched on and off, certainly in recent decades. To the right, in the Greenland, Iceland, Norwegian Seas, there is a somewhat more stable picture of deep convection there. It would appear that, as hinted at in the run-in, the Labrador Sea convection is the more vulnerable. Without having an overall collapse of the so-called conveyor belt circulation, this thermohaline circulation, you can have a smaller scale but perhaps still significant tipping point where you would shut off the Labrador Sea convection altogether and it would only switch over to the east side of Greenland. That is beginning to be seen in some of the models and might be encouraged somewhat by ice melt that is happening quite a lot up the west flank of Greenland and adding fresh water to the surface there, although it is not the only contribution.

I would say it is not the scenario we have been sold of a total collapse, but the thing that is more likely in the shorter term would be a shut-off for that region of deep convection. That would be some overall weakening and perhaps a step weakening in the overall overturning circulation, which we would see the impacts of, but they would obviously be less than if there was a total collapse and we lost both regions of sinking. Does that help, Mark?

Mark Lazarowicz: Yes. I will maybe come back, but Professor Wadhams obviously has a view as well.

Professor Wadhams: Yes, I spent a decade running a series of winter experiments in the central Greenland Sea on a European Union project, which was called Convection. We were measuring the deep convection going on there and found that it was reducing quite significantly, in fact, both in depth and in volume The sinking in the Greenland Sea and the sinking in the Labrador Sea form the vertical components of the conveyor belt. The Greenland Sea sinking has diminished very significantly because ice formation has ceased within that region in the last 10 years. There used to be a lot of pancake ice forming there in the winter. That rejected salt into the water , which made the surface water more dense and made it sink. You were getting an extraordinary phenomenon called chimneys, which we were investigating and detecting, where a mass of water sinks down close to the ocean bed-about 2,500 metres sinking in a narrow column-and that is one of the ways in which the circulation maintains itself. The volume of convection and the depth of convection in the Greenland Sea have diminished and are not likely to be restored unless the ice starts to form again. What used to happen was a seesaw-that if the Labrador Sea convection got weaker, the Greenland Sea convection got stronger and vice versa-but what we are now getting is a weakening of both of them so the whole circulation is weakening. This has already been detected by a reduction in the strength of deep currents. The circulation is weakening and will probably continue to weaken, but it is a slow process. It is not going to change things rapidly.

Q28 Mark Lazarowicz: Before you come back, Professor Lenton, just on that point, clearly you cannot predict what is going to happen with any degree of certainty, but it is clear there is a consensus, certainly among yourselves, including Mr Nissen, that this is a process that is clearly happening and that the difference may be with the speed and the extent of the change, but as long as warming continues there is no doubt in your mind that this will happen sooner or later. Then I was going to ask you-Professor Wadhams talked about possibly at the end of the century; Mr Nissen talks about years, perhaps-Professor Lenton, what was your time scale?

Professor Lenton: I think there is consensus that some abrupt changes appear to be starting to happen and that certainly ongoing climate forcing is going to trigger certain tipping point changes in the region within this century. On the convection I am agreeing with Peter’s story. Some of the impacts are that, if you have a shut-off of, say, the convection in the Labrador Sea, this adjusts sea level heights and would have measurable impacts, potentially up to 20 centimetres sea level rise along Boston, New York, the north-eastern seaboard of the US, just to inform you on those things having quite concrete impacts.

With regard to the timing, it is one of the reasons I try to work on these specific early warning methods to try to get a better handle on when particular thresholds might be approached. As I have said at the outset, we are starting to see some abrupt changes unfold now and we cannot rule out, for example, that we are already seeing the Greenland Ice Sheet retreat up on to land and take its icy fingers out of the ocean, if you like. The hope is that, if it does retreat up on to land, it would restabilise when it can no longer calve off icebergs into the ocean, but I would say we cannot honestly rule out that some thresholds like that one perhaps are already passed.

Q29 Mark Lazarowicz: Just to be clear, finally, on the question of the process, and the phrase "tipping point" has been used, in this case in particular it must be the case surely that when the circulation stops it is at the end of a process. It is not a gradual process where it slightly gets warmer or the UK cooler, relatively speaking, over a longer period of time. That may be the initial consequence, but eventually, if it stops, it is more likely to happen very quickly when a tipping point is finally reached. Is that a fair conclusion to reach or not?

Professor Lenton: It actually depends on the system, I am afraid. Although the language might lend itself to thinking of always rapid change, it really crucially depends on the internal dynamics of your system. An ice sheet will take, by human time scales, a long time to melt. We are not sure how long but it is determined by its own physics. Sea ice loss, on the other hand, as we are hearing, could be an issue in decades. It can respond much quicker. As for ocean circulation, the deep convection can shut off potentially from one year to the next, but to truly see the consequences climatically play out, you are tying that then to an ocean circulation that has much longer time scales involved, up to centuries. You see the effects unfold over that longer time scale.

Mark Lazarowicz: Longer-so centuries, as it were?

Professor Lenton: Well, a mixture, to be frank. You see some immediate effects from the fact that the ocean surface is coupled, quite interestingly, to the atmosphere in the Atlantic region, so you see coupled ocean atmosphere responses that can be quite fast. To get the full signal of reorganising the overturning of circulation of the Atlantic, I would talk more in terms of a century, I would say.

Mark Lazarowicz: I do not know if our other witnesses have anything to say.

Professor Wadhams: I think it is more rapid regionally. We have seen big changes in the Greenland Sea region and the northern North Atlantic, within a very few years of convection ceasing in the central Greenland Sea. Oceanic changes can have regional impacts fairly rapidly. If you look at the Atlantic as a whole the changes are taking decades, but regionally-and regionally is often what you are interested in, somewhere the size of a country-it can happen within a very few years for the ocean, and for sea ice I would say quicker than that-within a year or two sometimes.

Mark Lazarowicz: Mr Nissen, I think you think it will happen faster.

John Nissen: I am ambivalent about overturning the circulation. It could, in fact, help us in what it would produce, a shutting off of the Gulf Stream, and stop so much heat going into the Arctic and allow the sea ice to reform. It is just possible it could save us but we obviously could not depend on that. If we cool the Arctic, we can probably stop the overturning circulation shutting down and we can also stop the methane.

The thing that really I want to concentrate on, and want you to concentrate on, is this point of no return. It was Peter who said to me that he thought it was a point of no return once we lose the sea ice, and attempting to do geoengineering after the sea ice has gone is going to be impossible, meaning it is just impossible to get the sea ice back. I know that at the moment the heat that is going into the Arctic and the extra heat from global warming in the Arctic is melting the ice. To freeze the ice effectively and reverse this retreat process is going to be unimaginable. We are faced with a point of no return and we could be at it now, effectively. When so much is at stake, we have to assume the worst and act according to precautionary principle.

Q30 Zac Goldsmith: There seems to be a lot of disagreement in the research in terms of the pace of change. Could you say with confidence that there is a genuine scientific consensus of the basic premise that you are all deciding not the speed, but the direction of travel? Is there any doubt on the science?

Professor Wadhams: Yes, there are no doubts. There are disagreements about the speed at which changes are happening and will happen, but the direction of them I think everybody is agreed on. Really, we can see that happening in all the trends that we are measuring. All the environmental trends of air temperatures, changes in the ocean, and changes in the sea ice are in the same direction. It is simply how you extrapolate those changes into the future and predict, either through trends or by modelling, what is going to happen and how fast it will happen. The direction is very clear. We are going to get into a ghastly situation for the planet at some point and whether it is happening next year or it is going to take a few decades is the only question.

Zac Goldsmith: Does everyone on the panel agree with that?

Professor Lenton: I would say that I think there is a general agreement that we are losing the summer sea ice, for example, as a concrete example. There is plenty of argument about when. There is also plenty of argument about whether there is really a tipping point underlying that, which in the scientific literature is really an argument about whether the loss of the summer ice has carried some irreversibilities and difficulty to reverse. The question is maybe if one thinks about it from the impacts perspective rather than that esoteric scientific side.

Q31 Zac Goldsmith: In popular discussion, for instance, in everything from the blogs and internet to the journalists and some of the newspapers, there is a thread-there is a narrative there-that says that this particular example we are talking about today, this example of climate change, the thinning or disappearance of the ice during the summer in the Arctic region, is a myth. You have apparently very serious journalists like Christopher Booker, who is a well-known climate scientist-I use the term very loosely, but nevertheless; however, he has been banging this drum. Are you saying that there is zero credibility in the arguments that he is putting forward and which his supporters enthusiastically lap up? Is it total nonsense, what he said?

Professor Lenton: I have not read his argument, but it sounds-

Zac Goldsmith: He says year-on-year increases in the thickness and width-

Professor Wadhams: It is not only wrong, but it is insulting as well to all the scientists who are doing this work. Four years ago I was up in the Arctic in a submarine and we had an accident and a couple of the sailors were killed. It was very, very nasty and the submarine could have been lost. We were measuring the ice thickness. I have been doing this time after time and other polar scientists are doing the same, risking their lives to do these measurements. It is not just-

Q32 Zac Goldsmith: But are there any scientists doing these measurements-any credible organisations or scientists doing these measurements-who would dispute what you have just collectively told us is a clear trend? Is there no one out there?

Professor Lenton: The only recourse for the sceptic is that it is a point of information that the Arctic has shown abrupt natural climate changes in the past. We would not deny that. Between the 1920s and the 1940s there was quite abrupt Arctic warming that then fell away again. This is a relatively small part of the planet in totality so it can show more volatility in its climate. We know these iconic examples, in fact, of past abrupt climate change were very much Arctic and could have been to the order of 8°C in a decade, as recorded in Greenland ice cores. No one is arguing that humans had any hand in that. If it gets blurred with the broader issue of the anthropogenic cause then, of course, one should not deny that there is a strong role for natural variability as well as human forcing in the region, and maybe people who want to peddle a particular story can perhaps, if they are smart enough, play with that. I think that is only extra reason for concern, to be frank, to know that the regional climate has such a scope for volatility.

Q33 Zac Goldsmith: Just one small question, just to be clear. The sea level rise that will result, it would result not from the sea ice melting but from the Greenland ice melting, just to get that on the-perhaps nobody has said that.

Professor Lenton: The main sea level would come from the land ice melting into the ocean. Now we have to think about readjustment of sea-level height if you change, say, ocean circulation. Some places it goes up, some places it goes down, but those changes could be quite significant.

Q34 Zac Goldsmith: The points I wanted to raise you have covered very, very well so far, but the final point is that there has been a lot of talk about the positive feedbacks. Can you spend a few moments talking about negative? Give us a bit of hope. We want a few negative feedbacks. Are there any promising negative feedbacks?

Professor Lenton: Well, John touched on it a little. I think that if the ice-

Zac Goldsmith: Sorry to interrupt, the feedback you mentioned was the Gulf Stream. That would be a disaster for us. It may help prevent-

John Nissen: Exactly. It is a disaster in a sense but it would amount-

Zac Goldsmith: It is not a negative feedback, it is a disaster for us.

John Nissen: If it allowed the sea ice to re-form, that would rescue the planet in some way.

Zac Goldsmith: A deep ecology lesson; let us embrace that as a-

John Nissen: Incidentally, one very obvious thing that we have not mentioned, if you lose the sea ice, you lose your polar bears and you lose your whole ecosystem. That could impact on the marine food chain and so on because there are algae that grow under the sea ice, which feed into phytoplankton and so on, down the food chain. There is a big ecological impact if we allow the sea ice to disappear.

Professor Wadhams: I have been trying to think of some negative feedbacks but I cannot.

Professor Lenton: One concrete thing we are seeing is shrubs encroaching into the tundra, so we are seeing a low vegetation gain in shrubs and ultimately a northward march of the boreal forests. It may be a moot point whether that really would lock up more carbon, because the danger is it releases it from the frozen soil while gaining it in the biomass, so I do not think I would like to put my hand on my heart and say that would necessarily equate to a net sink. But if you were looking for good news stories, you might look in that direction at the terrestrial.

John Nissen: I have a counterpoint. I just read a paper that suggests that this northward march of forests is decreasing the albedo, so-

Professor Lenton: That is indeed true. The worry then is, if you put a dark tree over snow in the winter, that wipes any of the carbon sink. It is hard to find the good news in the high latitudes. You can clearly say that there are negative feedbacks in the climate system as a whole in that only half of our annual emissions effectively stay in the atmosphere. The land and ocean sinks are mopping up the other half, and those sinks are partly linked to, in the ocean case, CO2 dissolving into the surface waters and being subducted to depth in the North Atlantic region. As long as that circulation stays on and with us, it is a key part of the ocean sink.

Professor Wadhams: Yes, but the fact is that the kinds of regulatory mechanisms that Tim has mentioned, like the absorption of a lot of the emitted carbon dioxide by the ocean, are themselves getting weaker. In a sense, there is a positive feedback going on in that the existing negative controls are getting weaker. For instance, the estimates of what proportion of carbon dioxide that is emitted is actually absorbed in the ocean is that it has gone down from about 43% to about 41% in the last few years. That seems tiny, but it is actually a very large amount of carbon dioxide staying in the atmosphere because the ocean itself is getting less able to absorb it. The carbon dioxide that is absorbed is producing acidification of the oceans, which itself has a positive feedback in that it means that shells of marine organisms that used to sink to the bottom of the ocean after death and be lost to the planet’s climate system by forming part of the ocean bed-do not actually get down to the sea bed now without redissolving. That means that you are buffering back carbon dioxide absorption by the ocean.

I do fear that the feedbacks that one sees are either feedbacks that are reducing the strength of controls or they are entirely new positive factors like release of methane from formerly frozen ground. That is unfortunate but it does seem to be the case that, as you get a certain amount of warming, it activates new processes that act to increase the warming rate, with the possible exception of clouds. There is a lot of disagreement about what the climatic role of clouds is, and certainly if the ice retreats out of the Arctic you are going to have increased cloudiness over the Arctic Ocean from the increased evaporation. That may have a negative effect.

Q35 Dr Whitehead: There is a lot of disagreement about the relative ferocity of the methane effect. There was a paper a little while ago from Shakhova stating that methane release equal to 12 times the current atmospheric levels is "completely at odds with state of the art models and paleoclimatic evidence". Instead, she said, "The most likely scenario is a long-term chronic methane source made up of many small events". That is presumably on the same evidence that you have. Are these just differences of opinion? Are they differences of interpretation or difference of measurement?

John Nissen: Natalia Shakhova has produced these estimates that I mentioned, 50 billion gigatonnes of methane that could be released suddenly because there is a lot of instability in the methane structures in the shallow sea. She has done some extrapolation. They have done seismic measurements that show that the permafrost under the sea is perforated, and 20% of it is covered in these pingos.

Dr Whitehead: Pingos?

John Nissen: Pingo-it is a geological structure where the permafrost is perforated, allowing gases from underneath to vent.

Dr Whitehead: So there are many vents?

John Nissen: Yes. So potentially there is a lot of free methane from underneath coming up, and that is potentially a vast amount, and the warming in the sea is penetrating so rapidly.

Q36 Dr Whitehead: But is it not the case that one of the consequences of global warming is an increase in methane activities generally because of the increased decomposition of organic matter that results from the increase in temperature in general?

John Nissen: Yes.

Dr Whitehead: How different is this from that?

John Nissen: Permafrost on the land is decomposing, but that contains organic material that then decomposes through bacterial action, microbial action. Under the sea, the methane is already there. There is permafrost with this organic material as well, but the methane that is coming out is either from methane hydrate, which is a combination of methane, water and kind of ice structure, or as free methane from underneath the permafrost.

Q37 Dr Whitehead: By the sound of it, that produces a far, far more abrupt-and as you said, potentially very abrupt-release of methane compared with the projected gradual increase in methane activity-

John Nissen: Exactly.

Dr Whitehead: -as a result of overall surface warming in various parts of the world. So it is a very specific, as it were, one-off methane rush in one part of the world that would dwarf the general methane effect around the world in general. Is that fair to say?

John Nissen: Yes. I mean, one of the things that has been recently discovered or worked out is what has caused several of the mass extinctions in the past history of the planet, and one or perhaps two of them they think now have been caused by methane, and this is methane hydrate, which is this ice form of methane at the bottom of the ocean, that has caused it. You have to have quite a lot of global warming to get right to the bottom of the ocean, whereas we have it in a shallow sea warming and the methane is trapped there.

Q38 Dr Whitehead: I understand that, yes.

Professor Lenton: I feel I should comment on that. There was a Palaeocene-Eocene thermal maximum 55 million years ago. It does look like there may have been a large methane release, but it is important to know that that is over time scales of thousands and tens of thousands of years. My personal view on this, having done some work on it and feeling I know the field reasonably well, is that, yes, methane in the long run and methane loss from these frozen reservoirs will be a long-term significant amplifier. It might even double long-term warming, and by long-term I mean thousands and tens of thousands of years from, say, 3 to 6°C, but our current best models are that it is a chronic adding up of lots of small destabilisation events. It plays out slowly, partly because you have to propagate a warming signal not just at the bottom of the shelf or the bottom of the ocean, but through sediments, and that is not inherently a fast process.

As a point of information, it is important to know that these flooded Siberian Shelf permafrosts, which indeed are destabilising and losing their methane, that flooding is partly a relic of the recovery from the last Ice Age, the fact that the flooding there is relatively recent and has flooded the permafrost, so I don’t think it is all anthropogenic. I think we should be clear on that. I do not deny the waters there are warming up for the reasons we have articulated and that will only accelerate the breakdown, but when I have looked at the numbers, I am in the more sceptical camp as to how big the effect is. It is significant. I am not saying we should not research it, but I do not think the alarmist story adds up in what I have seen.

Q39 Dr Whitehead: This is just a personal puzzle. Assuming that the Gulf Stream switches off and therefore, as Zac Goldsmith has mentioned, some sort of deep ecological point of view that saves the poles because the ice starts forming, even though we have a Nova Scotian climate in the UK-presumably, if that starts happening, then that also triggers the recommencement of the current process. That is, it should start recirculating as a result of that ice reforming, at which point the ice will stop forming.

Professor Wadhams: I suspect it will not go that far. The Gulf Stream will not switch off, for a start. It is largely wind-driven and that part will keep going. It is the fraction representing the thermohaline circulation that is diminishing.

Dr Whitehead: It is the deep circulation of the funnel drop of water.

Professor Wadhams: Yes, that part of it is-

Dr Whitehead: That presumably has already recommenced with ice forming.

Professor Wadhams: The thermohaline circulation is composed of water going in the same direction as the wind-driven circulation. The Gulf Stream is largely wind-driven, but the part that sinks at high latitudes and returns southward at great depth, is driven by the temperature and salinity variations - the thermohaline circulation. What is happening is that the Gulf Stream will keep going as far as wind-driven aspects are concerned, but the overall flow will be weaker because of the thermohaline circulation significantly weakening. It is not going to be enough to really cool the climate. It will cool it to offset some of the warming-that is what we will be experiencing-but the Arctic will not be experiencing sufficient change due to that factor alone to bring back the ice.

The tipping point idea is that when you change the conditions acting, you come to a new state where you cannot go back to where you were before. It is a bit like growing old. If the summer sea ice disappears, the ocean will warm up and the structure of the ocean will change to the point where, if you cool the climate again, it will be difficult for that summer sea ice to form again, so you will get into some new kind of climatic situation that is different, and the same applies to the convection in the Greenland Sea.

Dr Whitehead: I understand, but what you are saying, which is what I was in a very simplistic way positing, is you would not get sort of an oscillation effect; you would get a paradigm change?

Professor Wadhams: Yes. I do not think that there is a way in which you will get an oscillation here; it is a one-way street.

Q40 Caroline Lucas: I wanted to come back to the subject of geoengineering. John mentioned it, but also Tim was fairly critical of it. We had an email sent around to the Committee also deeply concerned about it, so I wondered if you could say a little bit more about some of the risks and challenges associated with geoengineering, as well as some of the costs, if anybody wants to start with that.

Chair: I think John Nissen is going to go first.

John Nissen: Yes, okay. I will deal with the simple one, which is the cost, which is very small. We are talking about hundreds of millions rather than many billions per year, but compared to bailing out the banks and things like that, it is peanuts. That is not really an issue.

Chair: Do you want to just come in on the costs? Would you agree with that figure?

Professor Lenton: No, I would not say that it is-okay, some costings have been done for so-called stratospheric aerosol injections, and they have come out relatively low and have been much publicised, but this is the fine art of economic modelling. It is what you are including in your cost estimates. If you included the possible damages or risk factors, that could go up. To be honest, one should take a critical look at those very few existing studies as to whether they have really quantified it. It is fair to say that you can make a case that, compared to the cost of large-scale global mitigation of CO2 emissions, you can call it cheap potentially to put some tiny particles in the stratosphere on a regular basis. But you have to remember that, if you go down that path, you are committing not just the next generation but tens of generations potentially to keep doing that if you want to hold the global temperature steady while you still have the greenhouse gases there. You have to remember that we do not know precisely how much we have to add to counteract the current forcing, so it will never be a perfect cancel-out.

In the case of the Arctic, you can ask some interesting and probing questions as to the possible side-effects of reducing incoming sunlight, which obviously you have to do in the summer season because it is dark there in winter anyway. How will that impact on the ecosystem? I am also troubled when I see my colleagues who are more, shall we say, advocative for geoengineering and they start talking about meddling with Arctic cloud cover, but they do not necessarily realise that during the dark Arctic winter, the clouds are generally a warming thing, so they do not always get it, even the sign of their proposed intervention, the right way round. The precautionary principle would dictate first of all to tackle the causes of the problem, and that in this case happens to include a number of things that, like methane emissions globally, where 40% of the anthropogenic emissions should be able to be eliminated at net zero cost, in fact. The only problem with doing it is the cost of doing it has to be borne by relatively few companies or groups to do that, but the estimates are in the literature that big gains could be made on, say, cutting methane emissions, equally on black carbon emissions. The big issue here is that we are busy cleaning up the troposphere, the lower atmosphere, of our past dirty sulphate aerosol, and I suppose the case the geoengineers would make is to replace all that tropospheric sulphate aerosol with a relatively small amount in the stratosphere where it stays longer, because the stratosphere is stratified; that is why we call it the stratosphere.

I still do not think it is wise to do that on a regional scale, because by definition, if you do a regional geoengineering, you create gradients of forcing in the climate system, and the whole thing that drives the circulation in the atmosphere and the whole fact that we have circulation in the climate system is all about gradients of forcing, more sunlight becoming equated in the pole, so I would never be entirely comfortable with these methods, which are spatially heterogeneous, because by definition they all create gradients and they will surely create some changes associated with those gradients.

Caroline Lucas: I will come back to John in a second because I am sure he has some answers to go back with, but I just wondered, Tim, do you think, having said all of that, that it is still a worthy area of putting resources for more and more research?

Professor Lenton: It is a certainly worthy area for research, and the best possible outcome here may be that it acts as what one of the audience said to me beforehand; it is the opposite of the moral hazard argument. The moral hazard argument was that, once we knew that geoengineering-stratospheric aerosol injection-might be pretty cheap, it would stop us wanting to mitigate CO2 emissions. The limited public surveys that have been done are rather hinting at an opposite moral hazard, that when people see credible scientists talking about needing to research and possibly even deploy geoengineering, it tells you how urgent the problem is and suddenly people think, "Oh, really? We must tackle the root causes," so I don’t think research will hurt, especially not if it sends us down that line of thinking. It certainly is needed, because we are not mapping out and thinking in an earth systems way about what the many consequences would be of this kind of intervention, to be frank.

Q41 Caroline Lucas: You do not see any trade-off in research institutes between- If they are doing that, they are not researching more into the mitigation/adaptation side of it.

Professor Lenton: Not a great trade-off, because some of the research is happening anyway. There are complementarities, because we need to fundamentally understand the role of tiny particles in the climate system. Many of us wrestle with that anyway, especially effects on clouds in the troposphere, but also stratospheric injections of volcanic aerosol. There is an awful lot of complementarity and leverage on trying to get a better understanding of, for example, the Icelandic volcano and its effect on air travel as it happens and so on. It all connects together, so I do not think you will see a huge trade-off there, Caroline.

Caroline Lucas: Okay, thank you. Maybe we will go back to John, or Peter indeed, around those issues of the risk inherent in doing it and how that fits with the principle and issue of regional versus more global.

John Nissen: Yes. You have raised all sorts of things to counter. I completely disagree with you, incidentally, in your laissez-faire attitude towards the methane, because the precautionary principle says that we should not assume it is going to be the best possible situation, which is what you are describing, that the methane will take so long to come out that it will not have any appreciable effect on the temperature, only 0.1°C or so. That is on the methane.

On the geoengineering, if the sea ice goes by 2015 and the methane starts coming up, what else can we do but geoengineering? We have to do something on a large scale. It is intervention, therefore it is geoengineering. Then we say, "Well, what can we do?" Beggars can’t be choosers. When you look at what can be done, they are extremely benign things. Putting up a haze in the stratosphere, it diffuses the sunlight. If you make your particles small enough, you do not have a blanket effect.

Q42 Caroline Lucas: Would you say there are no adverse risks associated with doing this?

John Nissen: I am not saying there are none, but-

Caroline Lucas: You said you have to do something, and one could say the first thing one has to do is not make it worse, and there is concern that it could.

John Nissen: There is a certain man, Alan Robock, who has listed 20 reasons why not to, of the dangers in geoengineering, but I have been through them all and I said, "I don’t think any of your stats stood up," and I put it on the geoengineering list (google group) that he looks at, and he has not come back and said, "No, you are wrong about that and wrong about that." When I have looked at these things, it seems to me that they are not nearly as dangerous as one might think. For example, the danger that you might get the sign wrong, that you put up clouds and they start warming, that will not happen if you keep your particle size down, so you have to make sure you have small particles, so that is something you could do, or you do your warming at lower latitudes where the cloud reflection effect outweighs the warming effect, the cloud cover blanket effect.

Applying a precautionary principle to the geoengineering, what are the risks we are talking about? On one hand, you have the risk of an absolute catastrophe, passing a point of no return, a collapse of civilisation. On the other hand, you have a possible change in the pattern of monsoons, supposedly. I mean, that is one of the things that we are told are extremely dangerous.

Professor Lenton: It is.

Professor Wadhams: They are both dangers.

Professor Lenton: They are both dangers. I think we all agree that there could well be dangerous climate changes under way in the Arctic, but we are maybe disagreeing about what the key factors there are. You are right, Caroline, to ask about risk. We need the information to weigh up the risks of the changes we are seeing unfolding, and we know about the causes of those and we know we could tackle the causal agents of driving those risks and we could get quite a rapid payback if we reduce the short-lived forcing agents. Pretty much that could work as quickly, frankly, as having to develop the technology and deploy geoengineering, in my view, in this region.

Then, on the other hand, I am advocating research on what different geoengineering methods would be capable of in this region, but what is needed is a proper risk assessment of that-not just a cost assessment, but what would its impacts be? Personally, I think the clearest issue with the sunlight reflection geoengineering is that, once you are doing it and you still have the greenhouse gas concentration there and you have the temperature back towards pre-industrial or whatever you decided was the right level, the present temperature or whatever, you have effectively made a commitment. As long as you do not tackle the greenhouse gas concentration underneath, you have a commitment for many centuries to keep doing the geoengineering; otherwise, if you stop and if for some reason you stop the technology, you will get a very rapid warming that is much worse than the steadier one you have been trying to avoid.

Caroline Lucas: But they do not have to be either/or though, do they?

Professor Lenton: They do not, and in fact I am working on complementary approaches. I say mitigate the emissions of greenhouses gases first, then deliver carbon dioxide removal, because we will need that anyway, according to the current policy targets and all our scenarios, and then do the research, because we may collectively decide we need to bring the sunlight reflection methods into the mix later. That would be my hierarchy of priorities.

Q43 Zac Goldsmith: I suppose Tim Lenton just covered some of the points. I was going to ask you the question about the fact that we have never had a static line. It has always been changing, the natural ebbs and flow, and that is accepted. The moment you start trying to manage the planet, you lose sight of what the natural process is, you lose sight of the natural flow. As you have just said, you bind yourself to the process we have been trying to avoid, probably beyond that level, indefinitely, which seems to me to be the absolute height of human madness. In a sense, it is one of the most extraordinary things I have ever heard. I understand the feeling, the need to come to find a quick fix as opposed to dealing with all the political problems inherited, which is greenhouse gas and so on, but the idea that we will ever know enough about these vast biological natural systems to be able to control them without triggering unknown and possibly appalling consequences is to me the very height of madness.

None of you can identify accurately or agree on the positive and negative feedbacks. It has taken years for people to fully understand the impact of CO2, and we still have disagreement even between the three of you in respect to methane. This is a vastly complicated area. I do not believe there is a human mind on the planet capable of fully understanding the true complexity of the natural world. I accept where you are coming from, but to suggest that we can be clever enough to tinker here and tinker there and add a new component to the planet system and know the outcome for me is just moronic. I cannot think of another word for it. It is not a question, it is a statement-sorry.

Chair: Give us a comment in response to it.

Professor Wadhams: I agree with you in principle, because I have come very reluctantly to the view that we do need geoengineering. It is only a sticking plaster, as Tim said, but so long as you are still producing the greenhouse gases, the underlying forcing of the climate is there so you have to try to force it back and you have to keep doing so. But everything we do, so long as we have an industrial civilisation, involves interfering with the climate. That is what we are doing by burning things, by burning a few million years of fossil carbon in a few decades. We are already interfering with the climate in ways that we do not understand, and the more we do understand them, the more serious it looks. If we are causing a climatic change that is accelerating, and quite possibly accelerating faster than we think, and if this Arctic methane effect is giving us a boost that is going to really give a big upward kick to the rate of warming, then we have, at the very least, to research geoengineering methods. Many people say, "Well, let’s do this research as part of a group of strategies," but there is a good case for saying that it should be a crash course of research, that we should be spending a lot of money very quickly on both the science and the technology, especially the technology, of geoengineering, perhaps trying to concentrate on methods that do least harm-for instance, trying to whiten clouds at low level with water vapour rather than adding noxious substances at high level. But we must still act, because of the urgency.

Chair: Okay. I think we just need to move back to Caroline.

Q44 Caroline Lucas: Yes, we should move on. We could spend a lot on time on that, and we have further questions, really. That would be about the fact that we are taking evidence later on from both the Government and the Hadley Centre. Do you have a sense that UK policymaking in regard to the Arctic is well founded on the latest research, particularly in respect to tipping points? What we are trying to do now is gather some policy conclusions from-there is scientific disagreement, so it is a challenge, but I just wonder what your sense is of the UK policymaking to date.

Professor Wadhams: I should put my head above the parapet and say on the whole I think the policymaking and research in the UK are done at a high level, but there are certainly problems in terms of funding of research in climate change and environmental change, especially with respect to the Arctic That is a field where the responsible body is the Natural Environment Research Council, which doesn’t really have an Arctic strategy, in my opinion. It says it has, but it does not, and I personally have found a very negative response when it comes, for instance, to techniques that are very important from a climate change point of view, like measuring ice thickness from submarines. One finds enormous generosity by the Navy in making a nuclear submarine available freely for science, but when one goes to NERC and says, "Well, can you fund us to put sonars on to do these measurements?" they don’t. I get all my support from European Union funding and from the United States Navy and from the British Ministry of Defence, and nothing from NERC.

This is, to me, a staggering, incomprehensible thing. I think it is a function of the structure of NERC, the way it operates and perhaps the fact that it is too small. Perhaps we need a much larger single scientific research council, like the National Science Foundation in the US, which covers every branch of science. Britain, which is maybe a tenth of their scientific size, has a large number of research councils, each of which has parochial interests that affect the way that it does its job, so my personal view is we would get on a lot better if we had a single research council in Britain. We should look afresh at how Arctic research is being supported or not supported or directed. We should also be focusing a lot more on Arctic technology as well as Arctic science. If we are talking, for instance, about oil spills in ice, what we need is to be able to find ways of cleaning up oil blowouts via a very big technology effort. At present this is being done by Canada and Norway using funds redirected from the oil industry to science, and Britain could do a similar thing and that would be very important.

Caroline Lucas: Tim, any thoughts? Do we need a sort of UK strategy on the Arctic that would be a much more coherent set of policies, perhaps, that would be more joined up?

Professor Lenton: It should be clear from the afternoon’s discussions that, although we do not think of ourselves as part of the Arctic, we are close enough that how things unfold in the Arctic is going to have significant knock-on consequences here, so there could certainly be room for getting a slightly better strategic understanding of how the changes are unfolding. I already flagged up that our monitoring is not great and it is almost negligible for some of these systems-good for some, bad for others. We could do a lot more basic research in the kind of framework I guess Peter is talking about to get a better background data set on what is happening.

We have come back repeatedly to this issue-that it is short-lived warming agents that might offer quite a lot of leverage to mitigate the rate of change in the Arctic, and they do not sit currently well within the framework of UNFCCC and the conferences of the parties and the whole machine of trying to tackle CO2 emissions. That is no bad thing, because it offers avenues for policy progress that are not conflicting with that, but complementary. You can make good cases for tackling soot-black carbon emissions-based on health benefits in the regions where those emissions are coming from. We have seen a brilliant report from UNEP last year and several further studies really pinpointing how, making use of existing national and regional policy frameworks and other avenues, we could go to work on some of these short-lived forcing agents.

I would love to see the UK get its head around that and think more strategically on what can be done, because we are all frustrated by the lack of progress on the big CO2 problem, which we have to keep pushing on, but it is good news that we can do something that would make a measurable difference to the risk in the Arctic-that is, going with these other forcing agents.

Q45 Caroline Lucas: Can I just ask you whether you think the Arctic Council is doing enough to take the tipping point seriously in the Arctic?

Professor Lenton: I am not super party to it, but I have seen some of their material and I have seen them beginning to really take it seriously. I have seen at least younger members put forward ideas about the geoengineering issues, so it suggests to me they know urgent changes are happening. Through the Arctic Council is clearly one of the avenues of influence that could be exerted. What we are seeing in the Arctic is not conflict; it is sort of competition at the moment between nations, I would say. Oran Young is doing nice work on that and has a good intellectual understanding of how it is unfolding.

Professor Wadhams: The Chairman of the Arctic Council is at a meeting this afternoon, about 100 yards down the road from here at the Institute for Strategic Studies, on policy in the Arctic, and I think the very positive thing that they have done is to have started a task force on protection of the Arctic and on environmental change and how we deal with it. It is concerned directly with oil issues, but also with oil/climate interaction issues. It would be even more useful is if they became truly international and took advice and input from outside the eight nations of the Arctic, so that the observer nations, or nations that are involved in the Arctic but not Arctic states, could play a role. Britain obviously is one. There are other countries that have oil operations in the Arctic, like Italy, but do not have observer status with the Arctic Council. Work that other countries are doing on climate change in the Arctic and environmental protection in the Arctic should be taken on board more by the Arctic Council. I think they at the moment do slightly limit themselves because of the eight-nation character.

Chair: Yes, you wanted to come in on this, Mr Nissen.

John Nissen: Yes. You were asking whether the research councils and your advisers are giving good advice or whether it could be improved, and I think we really need a proper risk analysis done on what the risks are, as I have been talking about, because they don’t get discussed enough. We hardly ever see any papers that refer to the PIOMAS model of Arctic sea ice volume, which shows this precipitous descent towards the zero mark for the volume; furthermore discussions on the methane do not take into account the rapid disappearance of the sea ice, which acts as a protection on the methane. If you do the risks on the other side, what are the risks to the safe progress of human civilisation? What are the risks to the food supply if our climate warms way beyond 2°C? These risks need to be assessed and balanced, and I think if you do that, you realise that we are in a crisis.

Chair: I am just conscious of time. You wanted to come in?

Mark Lazarowicz: No, I am staying for a little longer. I am staying for a little bit more.

Q46 Chair: Yes, I am just very conscious of time, because we need to keep our quorum.

Just on that issue about whether or not the UK should have some kind of strategy policy direction other than what is there at the moment, I think the issue is whether that policy should be based not so much on exploitation in the area, but the overall concerns that there are for the planet throughout whatever process or so on there is or is not, and where should the leadership for working collaboratively from the UK’s perspective, with the other partners involved, come from?

Professor Lenton: The risk-framing is a good one, and technically, or in the scientific meaning, risk is the product of the likelihood of something happening and the impacts of it happening. There is certainly an awful lot of room for research to unpick the impacts of some of these scenarios we have discussed. We do have something of an intellectual lead in this country in terms of our ability to model and conceptualise on the tipping point issues, state of the art models and Hadley Centre, think about what it would take to give early warnings and get better information on the likelihood axis of the risk matrix. Very little is done internationally on the impacts axis of the risk matrix, so any efforts to tackle mapping out in any detail the impacts of these eventualities would be novel and we could indeed have a good go at that.

Q47 Chair: Okay. I am just conscious of time. I want to just move on very quickly, because we have had quite a detailed report from you, Peter, on oil and oil spills, and I do not think we have time now for you to rehearse the detail of the paper that you have presented us with, but that will be published for our records and as our evidence. I just wonder if you could perhaps just summarise the challenges that there are and the risks that are associated with oil exploration in the Arctic.

Professor Wadhams: Yes, thank you. It is a very serious question and, because of the present Arctic oil rush and the involvement of British companies in it, we do have a stake in what is going on with oil development in the Arctic. As the theme of Committee is protecting the Arctic, we should be thinking about what regulations we should be trying to encourage or initiate ourselves for our national companies who are operating and drilling under ice in the Arctic. Research in this area started about 40 years ago in Canada, and the most basic research was done early on when we were allowed to do scientific oil spills, which are not allowed any more, so progress is slower. Work done in Canada, in Norway and modelling work really have given us a clear picture now. This was discussed at an international conference that I helped organise in September 2011, at Fermo in Italy. The delegates concluded that if you have a blowout under ice, you are going to have something which is as bad as the Deepwater Horizon but in a different way The present plans of most oil companies are for drilling during the summer months in broken-up ice or ice-free water using drill ships. If they have a blowout near the end of summer, this will produce oil and gas coming up together in a bubble plume, and the gas will include methane. If they can’t cap the blowout off or drill a relief well before the winter, the blowout will operate right through the winter months, with oil and gas coming up under the ice.

As the oil-gas plume comes up under ice, the oil coats the bottom of the ice, and if the ice is moving, which is often at about 10 kilometres a day, it acts like a great sheet of moving blotting paper, absorbing the oil coming up under it, and carrying it away downstream. You will have a trail of oiled ice floes1,000 kilometres or more in length covering a whole swathe of the Arctic. The oil disappears into the interior of each floe, because new ice grows underneath it, so you have an "oil sandwich" which lasts all through the winter. Then the oil rises to the top surface of the ice in the spring and summer and retains its toxicity. By now it is spread thinly around such a huge area that it is very, very difficult to burn it by that stage or get rid of it by mechanical removal. The sort of horror story that we would experience if we had a whole winter’s blowout suggests that the biggest efforts should be made to design pre-engineering capping systems that you would design for each well, such that, if you have a blowout at the end of the summer, you can cap it off and prevent the oil from getting to the ice in the first place. You can do that within hopefully a few days, faster than drilling a relief well.

Q48 Chair: What is stopping that being used at the moment?

Professor Wadhams: There isn’t anything to stop it, and in fact, you can divide the oil industry into the serious companies who are there for a long commitment and that are doing the right things and are aware of these problems, and the sort of cowboy companies that want to come in quickly and get out again. The serious companies, which I think are all the Arctic operators except perhaps Cairn Energy, have serious contingency plans that include these capping systems, and in fact we have just seen last week that Shell’s proposals for drilling in the Chukchi Sea include stopping drilling one or two months before the end of the summer season and to have a pre-engineered capping system ready to go if there is a blowout during the last period of the summer. A regulation that the Canadian Government had already imposed in the past is you stop the company from drilling a certain number of weeks before the end of the summer season, such that there is time to either drill a relief well or cap off the well with one of these capping systems that BP eventually developed for the Gulf of Mexico. That would minimise the amount of oil that gets to the ice. Once the oil gets to the ice, the physics is going to spread it all round the Arctic and it will be very, very difficult to get rid of it by any method, so it is basically going to cause a real mess. Shell has these capping plans, and other companies that are working in long-term up there. ConocoPhillips, Chevron and others have these plans, but you have to look at companies that don’t have credible plans, and they are the ones that would need to be very strongly leant on.

Q49 Dr Whitehead: I think you have substantially hinted at what might need to change in terms of oil and gas extraction in the Arctic, but there has been the Fermo conference on this issue. Are the discussions, in your view, on what needs to change limited to discussions just ongoing between academics and oil companies, or would you say it is going further than that? For example, is there any serious sign that any sort of serious protocols that can limit Arctic drilling and, if it is necessary, make it to some extent catastrophe-proof, are taking place?

Professor Wadhams: I hope it is going further than just the academics coming up with things, because the Fermo statement (a statement of research needs produced by a panel at the Fermo conference), for instance, has been taken on board by the Arctic Council, and that has been fed into the work of their taskforce on Arctic protection. The Arctic Council can come up with agreements that have teeth-and they came up with one on search and rescue. Mostly these sorts of organisations are talking shops, but when they came up with an agreement on how to divide up the Arctic responsibility for search and rescue among different nations, they were doing something that was real, and hopefully the same thing will happen with their discussions on environmental protection in the Arctic. They will come up, one hopes, with regulations that will apply to all Arctic operators, no matter which country they are working in, and that might override or complement national regulations that Canada, Denmark, Greenland, Norway and Russia have developed on their own.

They may well focus on some over-arching regulations, like insistence on a capping system to minimise the duration of a blowout, and insistence on having or trying to develop new ways of cleaning up the oil afterwards. At the moment, most of the people who have studied the subject agree that once the oil gets under the ice, there isn’t a good way of getting rid of it, even in the subsequent summer when it comes up through the ice. It is spread around so much that there isn’t any good clean-up technique, but with research you may be able to find some new methods for cleaning up oil that is sitting on or under ice. A big research effort on technical methods would be needed, and, from what we already know, some regulations on the time of year at which drilling must stop, such that there is time to try to recover if they have a real disaster. This could be applied Arctic-wide by an organisation like the Arctic Council, which has international status.

John Nissen: May I just add one thing that Peter hasn’t mentioned? The methane escaping or the natural gas escaping is a major issue that I don’t think has been properly addressed, and I think you would agree with that; and we do not really know how much gas leakage could come and how to deal with it, especially if it is drilling in the ocean. How would you stop bubbles of methane from escaping in vast quantities? There is a particular danger if you are drilling into methane hydrate, either to extract the methane hydrate itself or to go through to a lower level, because there is a possibility of an explosive release of the gas ice form. If you do this on the shelf, the continental shelf edge where there is a slope, you could accidentally trigger an underwater landslide that would then disturb a whole lot of methane from all around the ocean, so that could be a mega-catastrophe.

Q50 Dr Whitehead: Could I just get a view? From what you are saying, and this particularly relates to whether there is some good practice among oil companies that might be disseminated, is the challenge in the Arctic a difficult one and worse than, say, drilling in deep water in cold water climates, but a difference of degree, or is it, in your view, a difference of principle such that it is very unlikely that one can say hand on heart there could be safe practices that could be developed in such a way that the extraction could be reasonably encouraged over a period?

Professor Wadhams: It is a difference of degree, but at present it is similar to drilling in deep water in the sense that there is a big question that has not been solved, but that drilling is going ahead anyway. In the case of deep water, the problem was that they had not solved what would happen if you had a blowout with the enormous over-pressures that you have in deep water, plus the fact that the compressible oil might not even come to the surface, In the Arctic the unsolved problem is that we do not have a way of cleaning up more than some tiny percentage of oil once it gets under the ice and into the ice. You could say that this is a question of degree, that it is no worse than the problem of deep water, but you could also say it is a difference of kind: we know that if we have a blowout in the Arctic and it is not capped off quickly, then there will be very widespread pollution of the Arctic, killing wildlife, birds and fish and polluting vast areas. We know that this is what would happen, so it is a question of feeding that into decision-making. Do you want to go ahead and drill, knowing that the risk is that if the oil blows out under ice, you cannot get rid of it? That is a value judgment. At the moment, the consensus view on what we know of oil/ice interaction is that an oil blowout under ice would cause widespread pollution of the Arctic if it continues through the winter, and this should be fed into decision-making that regulators adopt on whether drilling is permitted or not. You might say that you can permit it if you have these very rigorous restrictions in place on capping, for instance, that would minimise the risk.

Chair: Okay. I am really conscious of time. We must be very quick.

John Nissen: Yes. While we are trying to prevent the sea ice disappearing, because we can see what the consequences are even if they are slow ones, they are inevitable, and we have this point of no return. Until we are satisfied that we have the technology to cool the Arctic, surely we should not be doing things that are putting the whole Arctic at risk. Because the oil spills would lower the albedo, more sunshine is absorbed; so that is going to be a very bad thing from the point of view of trying to cool the Arctic. If there is a lot of methane produced when you drill, that is surely a danger that could be avoided-avoided until we have this situation under control, which I think we can do-I am bullish about that. We can do it if we go really hammer and tongs at this issue of cooling the Arctic, and avoid the drilling; then we have a really good chance of success.

Chair: Okay. I am afraid there we must leave it. You have all three been generous with your time. Thank you, and thank you for your efforts to bring everyone’s attention to the fragility in the Arctic. Thank you all very much indeed.

Prepared 21st June 2012