Select Committee on Science and Technology Minutes of Evidence



Examination of witness (Questions 40 - 59)

WEDNESDAY 15 MARCH 2000

SIR JOHN HOUGHTON CBE

  40. And are you satisfied that that sort of uncertainty is taken into account, when it comes to policy-making?
  (Sir John Houghton) Very much so, yes. I say very much so; sometimes fairly simplistic single numbers are bandied about, and perhaps simplistic views of what may occur with climate changes are bandied about, and that is probably inevitable, given the fact that people like one given number, or to use a given piece of evidence. But if you take the range of material that comes out of bodies of that kind you will find all the uncertainties represented within those bodies.

  41. The IPCC has concluded that the influence of human actions, especially emissions of carbon dioxide, is likely to be by far the most dominant factor determining climate change during this century. To what extent is the IPCC still involved in assessments of other factors and exploring other possible alternative explanations, not either this or that but the contributions that could be made by other factors that could contribute to climate change, such as some of the things we have mentioned already?
  (Sir John Houghton) Yes; each time we go through an assessment we look at all the factors, we look particularly at those factors that are likely to have changed in their scientific understanding, or changed for other reasons, during that period between assessments, and weigh them against what might occur from greenhouse gases. And the process of the assessment is not just looking at the effect of carbon dioxide and methane, and so on, but it is also looking at the sun and volcanoes and dust and particles and changes in land use, and all sorts of things, and we are constantly looking at possible other reasons for climate change which may make a contribution. So we are continually reviewing the whole scene.

  42. And what sort of proportionate effect are they likely to have, compared with carbon dioxide?
  (Sir John Houghton) The range, I suppose, is 5, 10 per cent, these other contributions, the likely range; there are some areas of substantial uncertainty where the contribution might be greater, up to perhaps 30 per cent, that sort of number.

  43. What areas are those?
  (Sir John Houghton) That is to do with clouds again, and the impact of particles on clouds, in particular, it is called an indirect effect of particles on clouds.

Chairman

  44. A point of clarification, Sir John. When you talk about clouds, clearly you do not mean clouds that appear on a Monday and are not there on a Tuesday, you are talking about the build-up of clouds due to some effect from earth that is making clouds denser, or more frequent, or more prevalent; when you keep on talking about how clouds can effect climate change, can you just give us an idea what you mean by that?
  (Sir John Houghton) Let me just give you an example, which we have spent a lot of time on, actually, in recent months, in our current assessment, and that is that there is a wide range of particles that enter the atmosphere from burning of forests, from sulphur dioxide, creating sulphate particles, and so on. Those particles have not only an influence of their own on the amount of sunlight reaching the earth's surface, because they directly reflect some of that sunlight away, or absorb some of it, they also act as nuclei for the condensation of droplets in clouds. Now, if you have a lot more particles in a cloud, instead of getting a small number of large droplets you get a large number of little droplets, and the properties of the cloud, the reflectivity of a cloud, the way it interacts with the energy flows, depends on the average size of a drop and the number of drops, and so on.

  45. And that could be very different in the 21st century from what it was in the 19th century?
  (Sir John Houghton) And that could change quite a lot, particularly in more industrial parts of the world, depending on the influence of these particles. So that is a possible reason for climate change. The largest estimates that people have produced are actually quite large, maybe 40 per cent, even up to 40 per cent of possible global greenhouse warming; we do not think those big numbers probably are justified, but some people are putting up numbers of that kind. On the other hand, it can be very small. So there is a wide range of uncertainty there, and this is represented in our current document.

  Chairman: That is very helpful.

Mr Beard

  46. But there was climate change before the last 200 years when carbon dioxide has been building up, and quite substantial fluctuations in climate. How do you filter that out from the effects of carbon dioxide, in your predictions?
  (Sir John Houghton) We try to establish what the reasons for those climate changes in the past have been; the big reasons, of course, for the ice ages, we know what has triggered those, and that is a variation in the earth's orbit round the sun. And we are in a warm, interglacial period at the moment; the next ice age is due in due course, perhaps in 50,000 years' time, that is the sort of timescale of the ice ages. So that is a bit beyond even the timescale of the general political operations. If you are looking at variations which occur over the period of a century then there have been variations in the past, we are not entirely sure of the reason for all of them, volcanic eruptions have been one, changes in the sun may well have been another. But those are small compared with what we expect to occur this century because of the vast increase in carbon dioxide, which is now way outside, of course, any level it has been probably for millions of years.

  47. The impression, Sir John, you are giving is that when you give advice, or the IPCC gives advice, the predominance of the advice is, as you have said already, around the greenhouse effect. To what extent are these other reservations mentioned at all?
  (Sir John Houghton) I give a lot of lectures on the subject, I talk, of course, to a whole range of people, including industry and others, and I emphasis the uncertainties too. But what I do say is that, if you are trying to create a likely scenario for the future and put probabilities on it, the probability of the climate remaining the same is very small, the probability of it being somewhere around a range of what the IPCC is talking about, that is the most likely range, the probability of it being so large that we are going to get real catastrophic disasters occurring is also very small.

  48. That was not what I was getting at. I accept that those changes will happen. My question is about the origins of them, the sources of them, and you are touching on other issues, variations in cloud, variations in sun activity, volcanic eruptions. To what extent are those being brought in as factors when governments are being advised on these issues?
  (Sir John Houghton) If we are discussing with government scientists then we raise all these points and show diagrams, and so on, which illustrate what we are saying.

  49. They are brought in?
  (Sir John Houghton) Because they are bound to ask questions about it, because, of course, some of them are raised so regularly in the media; but in any case we would do that, yes.

Dr Williams

  50. Would I be right in concluding, from our session today, that it is your feeling that most of the scientific objection to the consensus is actually from vested interests within the oil/coal lobby, rather than from scientists?
  (Sir John Houghton) Yes.

  51. What is your view of the green groups in this debate, thinking of Greenpeace, Friends of the Earth; have they been generally responsible, or have they exaggerated the argument for their own purposes?
  (Sir John Houghton) They vary from one green group to another, but some of the green groups are really very responsible. They do tend to emphasise, of course, the larger effects. On the other hand, some green groups have produced documents which are really exaggerations, with unjustified statements, saying, for instance, a statement like Hurricane Mitch is the result of global warming; it is not a statement which can be justified scientifically.

  52. What about the media? Have the media given the idea, say, that the Mozambique floods are due to global warming; you have got much better television, more of it, these days, and they have tended to say that there are more incidents of extreme weather now than perhaps five or ten years ago, and, again, they tend to attribute that to global warming?
  (Sir John Houghton) There is a tendency on the part of the media, in some of their programmes, to overemphasise, or to overillustrate the effects. We are going to get more stories, for instance, with global warming, of a kind that we are not sure about, we are not sure about more hurricanes, for instance, or more typhoons. We are sure that some sorts of storms have gone up in frequency in recent years, which is probably due to global warming, but we would be much more cautious in the statements we would make than the statements that sometimes come out from the media. On the other hand, of course, there are some media productions that also say, well, this is all rubbish, because they are relying on some of the lobby groups.

  53. Moving on now. The conference in Edinburgh, a couple of weeks ago, on genetically-modified foods, chaired by Professor Krebs, came to the decision, I think, that there should be an international body set up, perhaps modelled on the IPCC, to consider this whole area of GM foods. Do you think that that is a good model?
  (Sir John Houghton) I am with the IPCC and I tend to see its advantages, I suppose; but this is a good model. And one reason for that is, if I can just give a bit of history of the IPCC again and my involvement with it, when we began, in 1988, we had our first meeting of scientists on the issue, there were, I suppose, a significant number of scientists, good scientists, there, who said: "We don't know enough to say anything, let's keep quiet; we can't get involved in this sort of political stuff, you see, because we don't know enough to argue that." So we had a big discussion on that issue, should scientists be saying things, trying to make very responsible statements, or should scientists keep quiet; and the result of that discussion was that virtually all of them said, in the end, of course: "We've got to say what we know, and in order to say what we know we have got to discuss what we know so that we can have a debate about it". And I think what is a bit unique about the IPCC, it was helped, of course, by the international nature of the science in which we are involved anyway, there were international bodies dealing with meteorology and oceanography, and the like, which were there, so scientists were used to talking to their international counterparts, and so on; but what I think is fairly unique is that scientists have taken the trouble to try to debate amongst themselves what we know and what we do not know, because they feel responsible, and because there is a mechanism whereby the assessment can be carried out. Now in other areas of science, which are equally politically important, I do not think scientists worldwide have got together in the same way to argue about it and take the time and the trouble to try to come up with really good statements. And, I think, if we had not done what we have done, in the IPCC, we would be in a much more uncertain scene as far as climate change is concerned, just because people had not really thought about it hard enough.

  54. If we bring your model to the GM foods scenario, there is some difference, as I had understood, as to whether the new body—if there was this international GM body—should be accountable to the OECD or to the World Trade Organisation; or, in your own case, you are a United Nations organisation. Do you think—it is certainly my own view—that it is the UN umbrella that is fairest for GM foods as well; what would be your view?
  (Sir John Houghton) The parentage of the IPCC is one UN environmental body, the UNEP, and the World Meteorological Organisation, which is a UN technical support agency, so it is strongly scientifically based because both of those bodies are strongly scientific in their ethos. I could imagine there being some difficulty with a body like the World Trade Organisation being its parent, because the influence might be such that it might not be entirely neutral. If there were scientific bodies who could, bodies like FAO, for instance, would be very interested in the GM business, and I do not know whether they could be a possible parent. Though, having said all that, I also reflect on my experience with the aviation report, which the IPCC has recently done, which was partially parented by ICAO, the international body that joins the airline industries together, and that actually was no problem, they played a sensitive, positive role, and really wanted a good report which spelled out the science in a sensible way.

Chairman

  55. It could be horses for courses, could it not, really, depending on what the topic is?
  (Sir John Houghton) And who is prepared to do it, yes.

Dr Kumar

  56. Sir John, what importance do you attach to the climate change models and general circulation models in predicting and analysing climate change?
  (Sir John Houghton) Models are very important; and they are not the only thing, observations are even more important, because if you have no observations you cannot actually make any progress. But if you are going to put the observations and the data you have together, which come from a very wide range of components of the climate aspects of it, and so on, and if you are going to try to understand mechanisms, then you need a framework in which to generate that understanding, and a model provides that framework. And the reason we need a framework is because all the processes we are talking about are non-linear processes, so there is not a simple proportionality between an increase in this and an increase in that, it is much more complicated than that. And when you have many things varying; at the same time you have to find some way of putting together the forcing factors and the responses and adding them up, and the model does that for you; you cannot do it analytically because it is too complicated to do that, it is not mathematically possible, but you can do it by using numerical methods to add together the forcing factors and add together the responses. Because we do know, we have a very good knowledge of the physical laws and the chemical laws, and, indeed, the biological ones, which operate in different parts of the climate system, and in order to add those together you need to carry it out with a tool, and the model is that tool. The model can be quite a simple thing, involving an equational tool, in its very simplest form, or it can be a much more complicated thing involving many equations and many factors in a much more complicated model.

  57. How accurate are these models, would you say; is there a way of testing the accuracy of the models, that you have tested in any way?
  (Sir John Houghton) If you make a model of the climate, the first thing it has to be able to do, of course, is to describe the current climate rather well, with the current forcing, which comes from solar radiation, and the like, it has to be able to produce a response to the diurnal cycle, with a change during the day, to the annual cycle, that is the change during the year, through the variations that occur due to things like the El Nino phenomenon, and the like, or to other factors, volcanic eruptions. And you can test the model, over different timescales, by testing how it responds to things that you know about, which have occurred already or which regularly occur, and get a very good idea of how that response might be. And, to give you an example of something which has helped, I think, to give us confidence in models, more than we had before, in 1991 there was an eruption of a volcano in Pinatubo, in the Philippines, which put out a lot of dust into the high atmosphere, which was circulated around the globe, in a fairly uniform manner, actually, cut out some solar radiation, a few per cent, the average temperature of the surface and the lower atmosphere went down by about half a degree, over a two-year period, and the models produced that response quite well. But a more stringent test from that was that, as a result of that volcanic eruption, perturbations of the climate ocurred; there was an anomaly in the regional pattern of climate change. I do not know if you remember the years 1992 and 1993 but they were particularly mild winters in western Europe and particularly cold winters in the Middle East, there was snow in Jerusalem in both those years, I think, or very cold in Jerusalem in both those years. And the climate model in Hamburg attempted to try to simulate that response, and, in fact, they simulated it reasonably successfully, not perfectly, by any means, but the major anomalies which occurred in the regional climate change, as a result of that volcanic eruption, were reasonably well simulated by the Hamburg model. So that gave us some confidence in the use of models in simulating climate change on a global scale.

  58. Some people have proposed the fossil data studies, in measuring the changes in climate change; have you explored that?
  (Sir John Houghton) Yes. There are some models, a Hadley Centre model has been used to try to simulate the climate of about 6,000 years ago, for instance, with some success, at least as good success as you can test, because the data from that period is not very good, is not perfect by any means, but at least some of the features of the climate of that period have been well simulated, and others have gone further back, actually, to parts of the last ice age, and the like, in order to test models. So models have been tested against quite different climates which have occurred during the ice age, or since the ice age.

  59. And are there any reservations in the research community about these models that we have?
  (Sir John Houghton) There is no reservation about the fact that they are valuable and useful. There is much discussion about how certain they are and how accurate they are and how you actually establish that, in terms of the detail of climate change. Many of the models, of course, we can test models against each other, and there are, what, 20, 30, 40 elaborate, coupled ocean atmosphere models worldwide, you can compare the results from the different models. But then, of course, you would argue, and quite rightly, that many of those models have the same pedigree, some of them came from the same sources, or similar sources, they are all different in some regard, but in other regards they are very similar; so how good a test is that. And that is a question we often debate, actually, as to how well tested they can be. I think, the way our confidence has grown, however, over the last 15 years, since good models have been available, is interesting, because every time, I think, the models have improved dramatically in some technical way; there has been more confidence in the results; it is not obvious that that is going to be the case, actually.


 
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