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Mr. KARL. North America is similar to other major, large continental areas. So you can make the same statement for Eurasia, as well.

Chairman LIEBERMAN. Thank you, both. Senator Thompson.

Senator THOMPSON. Thank you very much, gentlemen. Thank you very much for being with us here today. It seems to me that one of the things that comes out of reading from your works and other experts' work is that there is a great deal of uncertainty and complexity involved in what we are dealing with here, from the work of the National Academy of Sciences and also the U.N. Intergovernmental Panel on Climate Change and others.

Obviously, many are strong proponents of Kyoto, but in 1999, more than 17,000 scientists signed a petition against it. It seems to me that there are questions with regard to the extent of the warming. There are also questions with regard to the causes of the warming. The question presented to us as policymakers is how much do we know at this point and what are the responsible policy options and choices in light of what we know and what we do not know.

Getting to the question of the extent of the warming, I have read-or some scientists have pointed out or alleged—that the climate is always changing and always has. In the Middle Ages, we had another warming trend. Thirty years ago, some people were concerned about climate cooling. Is that technically accurate and, if so, what is the significance of that?

Mr. KARL. I would be happy to address that, Senator. One of the major improvements that we have been able to achieve in the last 5 years is the use of paleoclimatic data or proxy data, and what this encompasses are measurements from tree rings, ice cores, corals in the ocean and historical records. These records have been painstakingly analyzed over the last 5 years by a number of different scientific groups to try and estimate what temperatures have done globally over the last 1,000 years or so. Unfortunately, the measurements are not complete enough to go back 1,000 years in the Southern Hemisphere, but for the Northern Hemisphere, we think they are.

This analysis suggests that our concepts of things like the Little Ice Age, the medieval warming period, perhaps were rooted in the accounts that we read from Europe. If you look at the globe or the hemisphere as a whole, what you see is a remarkable consistency in temperatures across the Northern Hemisphere the last 1,000 years. So when you put on top of that the instrumental record of the 20th Century, you see that the warming that we see in the last 100 years is substantially greater than anything we have seen in the last 1,000 years.

By no means do we have all the answers. We would like to be able to narrow uncertainties. I think the statements we are using now are saying things like, “It's likely that,” because we want to leave a little room for additional observations. But the best evidence suggests the warming today is very unusual.

Senator THOMPSON. Can you determine that there have been periods of time in our history where there has been a cooling?

Mr. HANSEN. Certainly there have been. There was a cooling comment about some scientists talking about mechanisms that would cause cooling. That actually is in my chart. The blue barsthe aerosols, most of the aerosols, tend to reflect sunlight and therefore cause a cooling, and it is a possibility that the cooling that we observed in that period was related to the aerosols.

As we started to get our energy systems going, we were producing a lot of aerosols and CO2. Recently, in recent decades, we have tried to reduce some of those sulfate aerosols, which are pure white and cause a cooling effect. The reason to reduce them being that they cause acid rain and other undesirable things. So it is good to try to reduce those. In the process, though, we accelerate the tendency toward warming. So that is why it is important to also attack not only sulfate aerosols, but the black carbon aerosols, because those aerosols cause warming.

Senator THOMPSON. May I ask this? Do we know enough about this particular subject and this history?

Mr. HANSEN. We do not know enough to

Senator THOMPSON. Extrapolate that the current trend is going to continue?

Mr. HANSEN. Right, because, you see, there are uncertainty bars on these, the black vertical bars. In fact, the aerosol changes are very uncertain. We do not have the measurements. It is clear we need to try to do some things, and we will need to adjust our strategy as we go along, as we learn more.

Senator THOMPSON. If my suggestion is correct, it does not mean that we should not do anything about it. It does not mean that we should not try to deal with it, or err on the side of safety in the long-term. But it does seem to me, from all I can gather and my limited knowledge of this area, that there is still an awful lot we do not know. It would be very difficult, based on where the science is and where the history and the historical analysis has been, to extrapolate any trend with confidence. It is kind of like budgets and deficits and surpluses around here. Whatever is happening at the moment is what we predict is going to continue to happen. I hope scientists do not do the same thing, but it is a good thing to keep mind, I think, as we go forward.

I also understand that some satellite measurements have been different than others in terms of the extent of the warming. Obviously, you have got regional considerations to take into effect. Some parts of the world are cooling, many are warming. In some cases, surface measurements have been different from satellite measurements—have they not?

Mr. KARL. It is an interesting aspect of trying to understand some of the details of what we see.

Senator THOMPSON. Do not try to make me understand it. We do not have time enough for me to understand all that. But I have a couple more questions, if you can give me a summary.

Mr. KARL. It is clear that if you look at the middle of the atmosphere—I think you were referring to satellite measurements—if you go back to the late 1950's, where we have weather balloons, the middle atmosphere and the surface warming is very comparable. If you look at the last 20 years, a smaller period where satellites have been able to provide additional information, you do find significant Senator THOMPSON. Alright, sir. Getting to the causes of warming, Dr. Hansen you especially have made the point that perhaps we are not emphasizing enough the non-CO2 aspects. I notice this bill creates an Office of Carbon Management and so forth. Obviously, CO2 is significant, but actually I believe that has been rather stable. CO2 emissions have been rather stable over a period of time—haven't they—while the other particulates and so forth have gone up?

Mr. HANSEN. The CO2 emissions have been, in the last 20 years, increasing at about 1 percent a year. That compares with about 4 percent per year from the end of World War II until the oil price shock in the 1970's. So we changed the growth rate from 4 percent to 1 percent. But if we allowed even 1 percent per year growth to continue 50 years, we would be in trouble. So we really need to change that i percent to more like 0 percent, and that does require some effort and some technology.

It is often assumed that CO2 is all the problem or almost all the problem. That is under the assumption that CO2 emissions continue to increase, so that every year we burn more fossils fuels than the year before, and that is not necessarily true. If we can decrease that growth rate down to 0 percent, then its contribution is not so overwhelming.

Senator THOMPSON. Both of you worked on the National Academy of Sciences report that did an evaluation of the work of the IPCC, and it has been somewhat controversial. The summary that came out was used in the media, in many cases, to say that what you were doing was endorsing Kyoto or certainly at least endorsing the IPCC conclusions.

One of your fellow panelists, Richard Lindzen has written in the Wall Street Journal about it, and says, “The panel was finally asked to evaluate the work of the United Nations Intergovernmental Panel on Climate Change, focusing on the summary for policymakers, the only part ever read or quoted. The summary for policymakers, which is seen as endorsing Kyoto, is commonly presented as the consensus of thousands of the world's foremost climate scientists. Within the confines of professional courtesy, the NAS panel essentially concluded that the IPCC's summary for policymakers does not provide suitable guidance for the U.S. Government. The full IPCC report is an admirable description of research activities and climate science, but it is not specifically directed at policy. The summary for policymakers is, but it is also a very different document. It represents a consensus of government representatives, many of whom are also their nation's Kyoto representatives, rather than scientists. The resulting document has a strong tendency to disguise uncertainty and to conjure up some scary scenarios for which there is no evidence.” 1

Would you concur or disagree with his assessment of the work of the NAS in this instance?

Mr. HANSEN. I am disappointed that the media takes such a simple perspective. We reaffirmed that there is some global warming going on, and that there is a danger of large climate change later

1 The article by Richard S. Lindzen referred to by Senator Thompson appears in the Appendix

this century. But that does not lead to the conclusion that therefore the solution to this is Kyoto. We did not address the appropriate policy responses. We did take pains to stress some caveats that should be associated with the IPCC assessment. In particular, right at the very beginning, our second paragraph of the summary, we said that the projections of IPCC that get very large climate change are based on the premise of a business-as-usual scenario, which has larger and larger emissions.

It is not obvious that will happen. In fact, in the last 20 years, there has actually been some deceleration in the rate of growth of climate forcings. The peak rate of growth occurred in 1980 and there has been a 25-percent reduction in that rate, due to the fact that we decided to phase out chlorofluorocarbons and the methane growth rate declined. So that is an example of the kind of strategy, that you can have other benefits from reducing some of these climate forcing agents. That is what we are trying to argue, that we need to look at the entire picture, not just CO2.

Senator THOMPSON. I am over time, but if you want Mr. Karl to respond to that, it is fine with me.

Chairman LIEBERMAN. Mr. Karl.

Mr. KARL. Commenting on Mr. Lindzen's comment, one of the things, I think, we tried to point out in the Academy report is any time you are necessarily taking a very large volume of work, like if you look at the IPCC full science report, and then you look at the technical summary and the summary for policymakers, it shrinks down. So it is very clear that you do not have the time to or the length of paper to explain all the uncertainties and all of the details of the changes.

So I think it is only natural, when you look at a briefer summary, that you do not spend a lot of time reading all the uncertainties, and clearly they are there in the IPCC report, and often beauty is in the eye of the beholder, and people can take all of those reports and selectively pull out individual sentences and try and craft either a very uncertain future or a very certain future. Senator THOMPSON. Sometimes commentators or

or politicians using scientific research and analysis to justify their opinions is not a pretty sight; is it?

Mr. KARL. It is not a pretty sight, but one thing I would say is in Shanghai, as we said in the Academy report, every change that was made to the report—because we went there with a draftthere were suggestions from the floor. They did not understand some comments that were made. They suggested alternative language. But for every change that was made, there was a scientist who was responsible for that section, who formed a group and eventually agreed to whatever change was put into the report on the summary for the policymakers.

Senator THOMPSON. Thank you very much.

Chairman LIEBERMAN. Thanks, Senator Thompson. Senator Voinovich.

Senator VOINOVICH. Thank you, Mr. Chairman. The two of us are on two committees, this Committee and Environment and Public Works, and I am not sure sometimes which committee I am before. I noticed that there is a movement to move climate change into our

Chairman LIEBERMAN. That is correct.

OPENING STATEMENT OF SENATOR VOINOVICH Senator VOINOVICH. I thank you for calling this hearing today. I think that this legislation does a good job of calling more attention to the issue of climate change without jumping to some of the conclusions, regarding the science and other issues, which have plagued other approaches. I am pleased, in particular, that it recognizes the need for the continued use of coal. I was interested in Dr. Hansen's comments.

Coal is now and will continue to be the most economical way of producing energy in this country for many years. We have a 250year supply of coal and we need to encourage clean-coal technologies. Unfortunately, Mr. Chairman, the previous administration was anti-coal and did everything it could to discourage its use, instead of promoting clean-coal technology and working with the utilities to improve their emissions to protect the environment and public health, and to provide low-cost energy.

I sincerely believe that until we pass a multi-emissions bill and deal with the issue of new source review, that we are not going to be able to utilize the technology available for coal so that we can have low-cost energy and move forward with improving our environment. The same applies to nuclear power. We cannot examine climate change and a national energy policy and ignore the fact that nuclear power is something that should be looked at, and again, until we deal with the political football of what we do with nuclear waste, we cannot move on with that option. But it is one that we need to move forward with.

As you know, Mr. Chairman, we did have a hearing in the Public Works Committee which examined the state of the science in terms of climate change, and I was impressed with the fact that there are still many uncertainties regarding climate change and the state of consensus on the issue is, I think, greatly exaggerated by climate change proponents and most members of the press. I noticed that Senator Thompson mentioned Dr. Lindzen's testimony and I am going to ask if that testimony that he gave in the hearing can be inserted in the record for today.1

Chairman LIEBERMAN. Without objection

Senator VOINOVICH. I am encouraged, although I think that President Bush handled this Kyoto Treaty issue-maybe from a public relations point of view, he could have handled it differently, because I know that Europeans are up in arms, and I ran into that when I was at the Organization for Security and Cooperation meeting in Europe and also at a NATO meeting. But I am encouraged that President Bush announced last week a broad policy initiative to further study climate change and the potential impacts, including an important joint venture with Japan to develop state-of-theart climate modeling.

The models that the U.N.'s IPCC has relied upon need additional research before we base a major policy initiative on them, such as what is called for by the European Union. We have to really im

1 The prepared testimony before the Senate Environment and Public Works Committee by

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