DR. WATSON: The first question is one for Bert Bolin. Why does it matter if there is a discernible human influence on global climate?
DR. BOLIN: If there is one at this stage that we can identify with what man is doing, it is very likely that it is going to increase. That is after all what we are concerned about. Still, as I said, we have not yet assessed and quantified the sensitivity of the climate system to changes of greenhouse gasses and aerosols very well. But there is a positive relation that is quite clear, as far as I can judge.
But maybe you aren't concerned about the warmer climate. I did not address impacts very much.
DR. WATSON: I would add to that. I think it starts to give us more confidence in elements of our theoretical models, which do of course predict significant changes in the absence of climate policies into the future.
I also believe it will fundamentally start to reshape the political debate internationally, I believe it is going to be much harder for certain delegates to argue there is no evidence of a human influence on the climate system.
On a much simpler issue, stratospheric ozone depletion, once we have established cause and effect between human activities and stratospheric ozone, it had a major effect on the international negotiations.
I was asked a question. How do you get politicians with a short attention span to favor support for long term research and actions? I'm not sure the problem in the U.S. at the moment is that they have a problem with long term research. The problem is, for some of them, they don't believe in these environmental issues. It isn't so much that you have to study them for the long term; they have supported rather well research on stratospheric ozone. They have supported quite well fundamental basic research in the National Science Foundation.
The problem we face at the moment is that some people who are rather influential in Congress don't believe global warming or global change is an environmental issue that we should care about at all.
As far as long term action, I think we have to convince people that climate change in the absence of policies is going to be very serious to both the United States and the rest of the world, and taking some near term actions will be beneficial to economic growth and the health of the average American citizen, let alone citizens around the world. So I don't totally despair that we can get them to move in the right direction, but it is a challenge.
To Tom Karl, Skeptics make a lot of the satellite data, indicating recent cooling. Can you expand on this? You obviously talked about it in your talk, but do you want to expand upon this?
DR. KARL: I think it is very important not to be misled by short records of 10 to 15 years. This has been unfortunate that at first, satellite records were looked upon as being in conflict with the surface records, because they showed warming. There was some notion that the satellite was not looking at the potential urban effects, so therefore perhaps the warming that we have seen at the surface was purely due to urbanization.
Indeed, when you compare those satellite measurements with the weather balloons, they are fairly consistent. The satellites themselves are not totally perfect. In fact, just last year the record was revised by about a six-hundredths of a degree Celsius per decade because of some biases. There is a lot of work that has gone into those records to try and alleviate biases. The satellites don't measure the diurnal cycle completely. As the satellites change, some of them measure some parts of the diurnal cycle, others measure other parts of the diurnal cycle.
But I do not believe there is a serious inconsistency between the satellite measurements, the weather balloons and the surface measurements. One has to be extraordinarily carefully about looking at a short record and making grand conclusions.
DR. WATSON: Thank you. It is quite clear that over one to two decades, one can clearly have a natural cooling trend that would easily offset any projected increase due to anthropogenic emissions of greenhouse gasses.
For Pieter Tans, what effects could the death or loss of coral reefs have on the CO2 system?
DR. TANS: It could have a tremendous effect. I did talk about it. I showed you a titration diagram, and I talked about bicarbonate and borate and CO2.
There was a lower diagram I didn't talk about, the pH. The pH of the oceans of course will go down as we add this carbon dioxide. At a certain point, coral reefs might become susceptible to solution.
If we manage to burn all the fossil fuel reserves, we might get into that range. In that case, it would also put a natural cap on the CO2 increase in the atmosphere, because the addition of calcium ions to the ocean and would increase of the ocean's capacity to hold carbon. In that sense, it is good, but of course, it is an ecological disaster of the first order.
DR. WATSON: A nice soft question for Dr. Bolin. In Madrid, several strong and particularly informative statements were edited out of the Working Group One report solely as the result of objections from non-scientists working in oil ministries in Saudi Arabia and Kuwait, based on briefs provided by the U.S. fossil fuel lobbyists. Are you worried about this new development?
DR. BOLIN: Yes, indeed. I think we have tried in the scientific community to accommodate different views, maybe a little too much. We haven't asked adequately for the scientific justification for some of these objections. It is a natural trend in a scientific debate, trying to see what kind of uncertainty we have.
However, it was a very important decision taken. That is, we did separate this very clearly on one occasion. It will be in the reports, an explicit statement that Saudi Arabia and Kuwait did not agree. I think this is very important, because it should encourage a much more clear distinction on matters of this kind.
It is not the purpose, I have said a dozen times, of the IPCC to just try to compromise into a common view, if there are different views, they should be reported. I hope this is done more in the future than it has in the past.
With regard to the lobbyists, I note that from now on, or soon, all lobbyists will have to declare from where they get their incomes. In that way, it will be much more obvious, not least in the United States, from where these views stem.
DR. WATSON: I think the answer by Dr. Bolin is very important. More and more, some of the IPCC plenaries are becoming negotiating sessions on particular sentences, because some delegations realize those sentences may be quoted back in negotiations on policy formulation under the Conference of Parties. I believe the approach taken by Bert Bolin and John Horton in one instance of isolating those two particular countries and putting them as a footnote needs to be done far more, and we can't keep going towards the lowest common denominator in all of our debates. A country that has a problem, or two or three countries that have a problem with a particular sentence should be willing to be noted in the footnotes as having a problem. I think that is the approach that will be taken far more in the future, rather than negotiating for hours to a lowest common denominator sentence that absolutely everybody can buy into.
DR.WATSON: A question for Tom Karl. Given we are seeing a signal of the greenhouse effect, how much of that signal can be attributed to anthropogenic activities? A nice easy one.
DR. KARL: The unfortunately part about that question is the whole basis of what we are trying to do. That is, it is impossible for us to say exactly how much of the signal that we see is due to any specific forcing. That is why we spend a lot of time on trying to look at estimates of natural variability and trying to detect changes that go above that estimated natural variability.
But what it does speak to is the fact that as climate does vary and change, and we see evidence for changes that exceed our estimates of natural variability, we then are confident that what we are seeing is in agreement with our expectations.
Another way to look at this is that climate could be varying naturally in a way that would enhance our ability to see particular climate variation or variability, or give us a false sense. That is, the globe might be warming naturally, just because the globe has internal variability in its warming, or it could be cooling, just because it has some internal natural variability.
So the question goes both ways. But our best estimates of natural variability would suggest that the signals that we are seeing are merging above and beyond that noise.
DR. WATSON: A question for Pieter Tans. What if we don't want carbon dioxide to increase to more than one thousand parts per million? For example, what if we want to keep CO2 from exceeding 450, what is the implication for burning all the fossil fuels?
DR. TANS: It would be Draconian. I showed the real long term effect of it. If we want to keep CO2 below 450 ppm permanently, I guess we would have to stop just about today, almost.
DR. BOLIN: There is in the summary for Working Group One very clear statements that if you wish to stabilize at 450, you mustn't emit during the next 110 years more than 600 gigaton, which is just about the average emission during the next century as the present emissions. But we also need from about 2100 onwards to get very much below this. So you can peak during the next few decades, but then you must get down. Whether that is possible or not remains for others to answer.
DR. WATSON: Yes, if you were to stabilize at today's global emissions, you would not stabilize concentrations. They would continue to rise up for many centuries, passing 500 parts per million by the end of the next century, going past 550, 560 within two centuries, and they would continue to go up, meaning that you would have to eventually reduce the emissions back to something like three gigatons of carbon per year. So even stabilization around 450 to 550 would mean very significant cutbacks in the total amount of CO2.
DR. TANS: Then after that period you would have to emit even less. Cutting back to three gigatons is not going to do it. You have to go back to zero.
DR. WATSON: A question for Bert Bolin. What future role do you foresee for the IPCC in terms of assessments vis-a-vis the role of SUBTA under the conference of parties, for those of you who don't what SUBTA is.
DR. BOLIN: IPCC I think has established its credibility in the scientific community. That has taken five years, I would say. SUBTA today has no credibility within the scientific community, naturally so. It is by and large a political committee. It is an open-ended committee where anyone can be represented. Therefore, it is not likely that it can achieve a scientific credibility of the kind that IPCC has.
That may be, but why change when there is something that works reasonably well. That is my question. The IPCC will continue. About every five years is what, not I, but scientists are others, think is a plausible interval between such major assessments. But in between, there is a need to get in much more of a dialogue with the subsidiary bodies of the convention in order to transfer information. But in doing so, as sharply as possible maintain the scientific integrity of the IPCC.
DR. WATSON: There is a question here for Tom Karl. Do we really have a long enough time series of ENSO data to say that it has been behaving in an unusual manner? How well defined is the normal ENSO cycle? I can comment that in the policy makers' summary, we say that since 1989, the persistence from '89 through '94 is unusual in the last 120 years. Maybe you would like to amplify.
DR. KARL: When we say unusual, we are saying that word in terms of both the direct observation we have and some evidence from coral records that also suggests that the variability that we have seen recently would still be considered unusual, inferentially suggesting that there are some very interesting things going on with ENSO recently.
DR. WATSON: There is a question here for Bert Bolin. In Rome, should calls for striking certain chapters of the Working Group Three Report on definition of the value of a statistical life arise, how will they be handled? For example, will you refuse to open all the reports or reflect this in the synthesis report?
DR. BOLIN: The working groups adopt the Summary for Policy Makers. When it comes up in the IPCC plenary, we must uphold that kind of a procedure. It is very essential. Otherwise, things start to just disintegrate.
Now, anyone can request that something be added to the minutes of the meeting in Rome. That of course will have to be accepted. But it is also important to clarify that acceptance does not mean that you agree with what is written there. The thing is, it is acceptance that this is a fair summary of what the scientific community has done. If politicians don't agree with that, that is their business. That is reasonably well reflected in the kind of Policy Makers' Summary that Working Group One was able to agree on, which is implicitly some criticism of the underlying chapter, in that it has been too stringently based on rather formalistic assumptions with regard to how you assess costs and benefits.
Procedures as we have them must be upheld very stringently.
DR. WATSON: A question to no one in particular. What is the global warming potential of water vapor? The answer is, IPCC has not calculated one. There is another question that is somewhat linked. I'll phrase it. Are carbon dioxide and water vapor included in GCMs for calculating global temperature? The answer is quite clearly, the way we drive the GCMs or the simple box Upwellan models of climate is by changing the emissions of gasses such as carbon dioxide, methane and CFCs and nitrous oxide into the atmosphere, and looking at the response. None of the GCMs assume a change in emissions of water vapor, but water vapor should respond to changes in the temperature structure of the earth's atmosphere. Hence, water vapor, both in the lower and upper troposphere, is a feedback mechanism to the perturbation or the change in radiated forcing of greenhouse gasses. Hence, we use water vapor as a response to forcing, not as a forcing mechanism directly in its own right.
So clearly, the GCMs do take into account changes in both carbon dioxide and water vapor, and their influence on the radiated balance both in the troposphere and the stratosphere, both are quite important.
DR.WATSON: A question for Tom Karl. Why do you suppose there is no evidence of increased incidence of extreme drought in the warm season within the USA?
DR. KARL: I think there are two reasons that that has not occurred. One is, the 1930s drought event in the U.S. was such a spectacular event, it may indeed be very ill-advised to focus on looking at changes in drought frequencies in the U.S. as being a greenhouse signal, simply because it would take a long time for that type of event to be smeared out in the record.
Secondly, we have found an increase in cloud cover over the U.S. Part of this could perhaps be due to the El Niño southern oscillation event. Part of it also may be related to natural variability. Another part could be related to indirect effects of sulfate aerosols. All these are possibilities. But nonetheless, the addition of cloud cover does tend to make the maximum temperature less than what it might otherwise have been. Therefore, we don't see a tremendous rise in the increase of extreme events associated with drought.
If you look at the records, there is a slight indication of a greater portion of the U.S. having more extreme and severe droughts, but it is very slight. We would be splitting hairs to say it is anything other than no change at all. But again, the drought event in the '30s, that really stands out.
DR. WATSON: A question for Bert Bolin. Your correlation coefficient was 0.3 for modeled and observed delta temperature. What is the statistically significance of that number, and is the correlation convincing to the eye?
DR. BOLIN: Yes, it is convincing to the eye. You can look up the picture in Chapter 8 of Working Group One, where this is clearly brought home. It is much better that you look at that than let me explain it to you, because those writing that are much more knowledgeable than I am. But it is a clear indication that the correlation between model and observed patterns has increased with time over the last 20 or 30 years.
It is not an exact agreement in any way, because of the natural variability, essentially. But there is an increasing resemblance between these two patterns in the course of time.
DR. WATSON: In fact, if you look at the diagram shown by both Bert Bolin and Tom Karl, the model which had CO2 only, and look at the pattern of the CO2 only and the observations, you have a negative correlation that is getting worse with time; it just goes down. If you then bring in the fact that there has also been a change of sulfate aerosols and other aerosols and a depletion of stratospheric ozone, you find a positive correlation between the observations and the theoretical models increasing with time.
So I think it is rather convincing. We saw some of this information in Madrid. It is obviously in the assessment documents. It is rather convincing, even to the eye. So I think the point Tom Karl made is the most important. Any one piece of information could be challenged. It is the ensemble of all of the information, the agreement of the global mean annual temperature over the last hundred years with the theoretical models, that take into account both greenhouse gasses and aerosols. It is the latitudinal and longitudinal distribution and the vertical distribution, when you take all of that ensemble into account, then it starts to become quite convincing that you can make this cause and effect statement, as we have in Working Group One.
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