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Mr. EHLERS. Reclaiming my time.

Dr. MICHAELS. And obviously the American taxpayers' dollars are involved. It does concern all of us.

If it is financed by America tax dollars, it certainly does.

Mr. ROHRABACHER. Mr. Ehlers?

Mr. EHLERS. Thank you.

The much broader question is addressed to all three of you, and that is, first of all, just a comment.

Historically there have been substantial fluctuations in climate. I come from the State of Michigan, which was under more than a thousand feet of ice, a mere ten thousand years ago. And that occurred without global warming or global cooling of the sort we are talking about here.

It seems to me that your entire emphasis has been in talking about temperature change, and I am interested in what other climate changes are being looked at or that you have looked at.

For example, the real issue is, if the greenhouse gases are there, and I think there is substantial evidence that they are there, we are dumping a lot of energy into the atmosphere, actually into the earth's atmosphere system.

What other effects are rising from that, other than temperature effects?

You may well have very dramatic climatic changes without much of a temperature change, largely because there is so much energy stored in phase changes between the solid and liquid, and liquid and vapor phases.

Are you looking at, or are others looking at issues relating to that, such as the increased amount of water vapor in the air? Which can have a dramatic impact without a great deal of temperature change.

How is that factored into the models?

What validity does that have?

How does that affect the temperature changes you are referring to?

How does it affect the weather intensity, particularly bad weather intensity across the globe, and so forth?

Dr. MAHLMAN. I will try to speak to that from the perspective of what the models are attempting to achieve.

A mathematical model of the atmosphere is a self-consistent solution of the equations that you know; force equals mass times acceleration, the first law of thermodynamics and conservation of matter are basically the equations that we know, and solve for the case of earth.

And so we do not predict just temperature, we predict wind, we predict precipitation, we predict clouds, we predict circulation of the ocean, we predict the state of sea ice.

All of these things are output variables of the model.

And so there are various aspects of model predictions that are related to the other variables that have their own degrees of uncertainty associated with them.

For example, the prediction that water vapor amounts will increase in a way that is self-consistent with the temperature increase amounts is a very strong prediction.

The prediction of whether or not we will get more rain in Washington, D.C. area is a very shaky prediction because it demands a lot of local physics, if you will.

The prediction of changed circulation of the ocean is one that is a robust result of the prediction of greater rainfall in higher latitudes some hundred years from now.

The question is, does mother nature know about this or not? That is the thing we grapple about. Where are the models wrong? Where are our physics wrong? Where are our theories wrong? And we use data to try to make that keep us honest, if you will.

There are lots of statements being made about increasing numbers and intensities of storms, for example. Insurance companies are very concerned.

My own opinion is that the scientific jury is still out on that. That there are a number of complexities and confounding factors that make it difficult to state there will be more intense storms or there will not be more intense storms.

And that, your question helps me define for you the struggle we have to try to define what we know and what we do not know, and how to communicate that to you in a way that is comprehensible. Mr. ROHRABACHER. Mr. Ehlers, you have time for one more question. Actually, you have gone over the time, but any last question you would like to ask.

Mr. EHLERS. I wanted to ask a question. Let me just make a statement, and you can respond to that.

It seems to me that some of these other effects are going to be much more worrisome to us than the temperature change; now I recognize they are interrelated.

But the water vapor change, for example, can have a dramatic effect on rainfall patterns. The beautiful weather in California might in fact become midwestern type weather, and you might actually have a green state, whereas other areas that are currently fertile might turn into deserts, as North Africa has done.

And I think it is, my comment is I think it is a mistake for everyone to talk simply about global warming, and discuss it in terms of that being the problem. I am much more concerned about the climate change that can occur and the effect that has on people and their ability to have enough food to eat and so forth.

Dr. MAHLMAN. Could I very quickly respond?

This is what the IPCC process attempts to do.

That it is well more than global warming, that global warming is the paradigm by which we address the problem because that is what is being forced.

And much of the impact side will be discussed in panel number two today, I believe.

But there is a fundamental truth that I believe you need to understand: is that the things we are very highly confident about are not as useful for impact assessment as those things that we are less confident about.

That is a truth that is going to remain with us for awhile.

Mr. ROHRABACHER. Thank you.

Dr. Guerrero, did you have

Mr. GUERRERO. I would completely concur with that remark.
Mr. ROHRABACHER. Thank you very much.

Mr. EHLERS. Thank you, Mr. Chairman.

Mr. ROHRABACHER. Thank you, Mr. Ehlers.

And now we will have, Ms. Rivers will be able to ask whatever questions she would like and you have your five minutes, Ms. Riv

ers.

Ms. RIVERS. Thank you.

I guess I want to start out by putting my own biases on the table because in my district, I have a large scientific community in the west side of the district that may have views on this that probably will differ from people on the east side of my district where there are 16 automobile plants, and they are very concerned about possible outcomes.

So my desire, in this debate, and in ultimate decisions of this body, is to make sure we are moving forward to understanding this situation and making reasonable policy decisions. So I do not have a particular interest in a particular outcome.

One of things I wanted to ask Mr. Guerrero, you know, we may not all of us here understand the first law of thermodynamics, but thanks to polling that we use regularly, we understand the idea of plus or minus so many percents.

And it is interesting to me that often times in this area, when uncertainties get discussed, they get discussed in only one direction. That any uncertainty must be resolved in the direction that we are projecting too much.

Is there any possibility that the uncertainties can be resolved in the opposite direction, that we may be projecting too little change or too few consequences?

Dr. MAHLMAN. May I speak to that?

Ms. RIVERS. Please.

Dr. MAHLMAN. I think the question you have raised is absolutely fundamental, and that as a person who is interested in how mother nature works, rather than to make a political point of one kind or another, I do not care which way our knowledge is uncertain. I am trying to find out what the truth is. Okay?

And when you have made your best estimate of the way things are, it automatically says that you do not know whether you are wrong on the high side or the low side.

There are many, many examples of both kinds of uncertainties giving a lower number than you expected or a higher number than you expected. Okay?

And I would say uncertainty knows no politics, it just is.

Ms. RIVERS. Thank you.

Mr. GUERRERO. To reply to your question, I would say that that degree of uncertainty is expressed in the range. When scientists talk about a global surface temperature range by the year 2050 of one to 3.5 degrees Fahrenheit embodied in that range is the sense that it could be on this side, it could be on the low side or on the high side.

And fundamentally what affects that are key assumptions such as our inability to model successfully cloud formation and cloud feedback processes which influence a lot of that range.

Ms. RIVERS. Okay. You raised concerns, Mr. Guerrero, in the difficulty of the computer models or the difficulty, given our level of

ignorance, we are trying to create these models, and I understand that frustration and I see it across all of the literature.

The question that I have is, if we continue, is there an expectation that the models will get better over time? In other words, if we maintain the research, are we likely to just stay stagnant or are we likely to improve our ability to do the forecasting?

Mr. GUERRERO. There is no doubt that as we continue to learn more about climate systems processes and to increase our computer capacity, we will be able to have a better predictive capability.

Ms. RIVERS. And if we make funding changes so that there is less opportunity to do the modeling, less opportunity to do the research, will that move us forward in terms of our understanding or production of efficient models?

Mr. GUERRERO. I do not want to get into a debate over how much to fund these activities. I would simply observe that there are some of those activities that are more critical than others.

And what I would say is important, however. Much resources are allocated to funding, that they be allocated to the areas where there is the highest potential payback in resolving the current uncertainties.

Ms. RIVERS. Dr. Mahlman, I have a question I made in my notes last night when I was reading my materials. The whole issue of aerosols and the impact they play, aerosols are sulfur dioxide, right?

Dr. MAHLMAN. Yes.

Ms. RIVERS. So talk to me a little, I mean, it is presented ashere is an antidote to what is happening sometimes is the aerosol. My question is, both sulfur dioxide and CO2 have effects in our atmosphere, what is their comparative life span in the atmosphere? Dr. MAHLMAN. Okay, I would be pleased to speak to that.

First, the presence of sulfate aerosols, which are caused by oxidizing of sulfur dioxide, do exert a cooling effect on the planet. We do not know how much. That is a very important point.

This is the point I disagreed with Dr. Michaels in that I think we do not know how to quantify that very well.

But what we do know is that the sulfate aerosols are a result of sulfur being released from burning of fossil fuels. Okay?

Now the thing that makes this interesting is that if you are looking at today's record, sulfate aerosols are producing a cooling offset. And this is a hard concept to get across. But the lifetime of sulfate aerosols in the atmosphere is roughly one week. The lifetime of CO2 molecule is roughly hundreds of years. Okay?

And what that means is that aerosols are not increasing as you keep burning at the same rate, but CO2 keeps increasing. So if you look for very long times in the future, with constant emissions of burning of fossil fuels, the aerosol effect gets less and less because it does not keep increasing.

Ms. RIVERS. How do we know that the aerosol is not-I mean, how do we know it is counteracting? I mean is there also a possibility it is masking the real problems here?

Dr. MAHLMAN. That perhaps is a theological question that I cannot get at. But the simple truth is that you add aerosols to the atmosphere, it has a tendency to cool the atmosphere.

Okay, you add carbon dioxide, it has a tendency to heat the atmosphere.

Mr. ROHRABACHER. You have time for one more question.

Dr. MICHAELS. I would like to follow onto that, if I could.

Dr. Mahlman's correct. The residence time of aerosols is on the order of days in the atmosphere.

That leads us to a very interesting problem. I just happen to have this planet down here.

[Laughter.]

Ms. RIVERS. I saw this on MTV.

[Laughter.]

Dr. MICHAELS. Hopefully, I can do a little better. All the aerosols are produced in the northern hemisphere. There is very little industry that produces the aerosol in the southern hemisphere.

And the amount of air that exchanges between the northern and the southern half of the planet is very, very low. It is a relatively small percent. So that the southern hemisphere is virtually sulfate free.

Now there is a paper in the literature you might want to take a look at, in the Journal of Technology from awhile back, because it tested the hypothesis whether the climate models that do not have aerosol in them-and please follow me-fail worse where the aerosol is and do better where there is no aerosol, a reasonable test, wouldn't you think?

Well, in fact the match-up of observed patterns of climate over the last 50 years in the southern hemisphere in the non-aerosol climate models is zero.

The point that I am trying to make to you, aerosols may have some effect. I believe they do, particularly in the northern hemisphere, but they are not a sufficient cause-please listen-they are not a sufficient cause to explain the difference between the projected and the observed warming, which is why I needed that high latitude data.

Ms. RIVERS. I want to ask Dr. Mahlman to respond.

Before I do, I support you in your need for that data, and I do not think this body would be diminished in any way to send a letter requesting that information. I think if we are going to build global policy on science of individual scientists, we need to have access to that, and I agree with that.

Mr. ROHRABACHER. Thank you, Ms. Rivers. And if you have one more question, go ahead, but we do have

Ms. RIVERS. I wanted Dr. Mahlman to respond to what Dr. Michaels just said.

Dr. MAHLMAN. Well, I happen to be a strong advocate of serious diagnostic research on what I will call the attribution question, which Dr. Michaels just spoke to.

Namely, how do you use the current data to evaluate the credibility or lack of thereof of theoretical or empirical predictions?

What we recognize is that there are many, many aspects of the climate system that vary naturally on regional scales on time scales of decades. And a good climate model is one that simulates not only the mean but its variability reasonably well.

Models do a fairly decent job of that, not wonderful, but a pretty decent job. And what you find is when you weigh in that natural

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