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Mr. ROHRABACHER. Just a point of clarification before we move on there to Dr. Nierenberg.

You mentioned what would happen in these various countries if, you said, there was a one meter rise in the ocean?

Are you projecting, or is someone projecting that there is going to be a one-meter rise in the ocean level?

Dr. WATSON. The IPCC Working Group I is projecting that by the year 2100 temperature would be 1 to 3.5 degrees centigrade warmer, and therefore sea level would be between 15 centimeters and 95 centimeters. In other words, within 5 centimeters of 1 meter by 2100.

But even then, even larger changes thereafter, even if we stabilize climate, in the year 2100 sea level would continue to increase for another couple of centuries.

So the answer is, yes, it is within the feasible range of our projections.

Mr. ROHRABACHER. So in 100 years, you are not predicting the 1 meter, but you say that after that it could well continue to rise?

Dr. WATSON. Our best estimate is 50 centimeters in one century, although it is not implausible it could also be one meter. Thereafter, there is no question it could continue to rise to 1 meter and greater.

Mr. ROHRABACHER. Okay. We will get back to that a little later. Dr. Nierenberg?

STATEMENT OF WILLIAM A. NIERENBERG, DIRECTOR

EMERITUS, SCRIPPS INSTITUTE OF OCEANOGRAPHY Mr. NIERENBERG. Mr. Chairman, I am grateful for this opportunity to place my views on climate change and modelling before the committee. The testimony is based largely on two documentsProgress and Problems. A Decade of Research on Global Warming, The Bridge, (National Academy of Engineering); and Looking Back Ten Years, a publication at IIASA. I hope these can go into the record, Mr. Chairman.

Mr. ROHRABACHER. It is so ordered, with no objection.

Mr. NIERENBERG. I begin by repeating what I often feel is a necessary prelude to a presentation of the issues. There is no question in my mind that the current anthropological growth of CO2 in the atmosphere ins bound to influence the climate. The question is not whether but when, how much, and the nature and the magnitude of the effects.

The fixing of when has taken an interesting turn. Ten years ago, discussion of effects centered around the middle of next century, often the year 2040. Now, almost universally, climate change effects are normalized at the year 2100, 105 years away from the present.

As an example and I have to differ—an average sea level rise is projected by current models to be about 30 centimeters, 1 foot, at that time, by the year 2100.

This rate also seems to be consistent with the early returns from the TOPEX satellite measurements.

I should be wanting in this recital if I did not direct your attention to the large difference between this result and earlier predictions of an order of magnitude larger changes.

It was only 15 years ago that a leading scientist predicted 25 feet in decades. We now have 1 foot in 105 years.

The number that surfaces most often in the discussion of climate is the change in the average global surface temperature change. The data for the past 100 years has been painfully and methodically pieced together and shows a rise of about 0.6 degrees Centigrade.

Unfortunately—I hate to read the rest of this paragraph, because Congressman Ehlers preempted my remark at this point-unfortunately, this is the least interesting aspect of climate change.

What is crucial is knowledge of the change in the statistical behavior—and by that I do not mean the average; I mean the sigma, the root mean square variation of the quantity such as rainfall, storm frequency and intensity, flooding, coastal storm surges, and so on.

By contrast, we can visualize an induced change that increases cloud coverage to the extent that the temperature rises very little, but clearly this is a definite climate change.

The weaknesses of the models is most clearly demonstrated by the historical observation that, since the original Charney report of the NRC in 1978, the National Academy of Sciences report of 1983, the IPCC report of 1990 and today, the spread of the temperature rise between the 15 or so climate models worldwide remains-it has not changed at all-between 1.5 to 4.5 degrees centigrade. It is correct. The previous speaker has knocked a half a degree off both limits—for an anticipated doubling of the atmospheric CO2.

This variation between the models is also reflected in lack of agreement in many of the predicted regional changes which are so important.

You have heard-and I am repeating—that the primary reason for these disagreements is the poorly represented internal radiation transfer properties and the overall effect of water in clouds, cloud formation, and water vapor.

This is in recognition that water in the form of clouds and vapor is the primary greenhouse gas. CO2 is not. Its changes, however, indirectly affect the water via feedback effects.

This has been recognized for years, going back at least to the 1983 NAS report, but it is only recently that serious field programs have been undertaken to formulate a better parameterization of these phenomena. The ARM and CHAMPP programs are in this category.

The other element of time that is crucial and has been mentioned several times is the lifetime of the excess anthropogenic CO2 in the atmosphere. This is a most important number-it is the most important number for policy considerations.

Here the advent of the coupled ocean-atmosphere model has made definite impact. What is being discussed here is how quickly would the atmosphere relax to a steady state or even its original unimpacted states if the anthropological impact of CO2 was severely reduced or even curtailed.

The base assumption is that, one way or another, fossil fuel reserves will be exhausted in several hundred years leading to a cutoff in the injection of CO2 into the atmosphere.

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At the time of the 1983 report, the then-current calculation in the literature proposed a behavior based on a 1000-year exponential lifetime for the disappearance of the excess CO2 in the atmosphere. That is, that that concentration would be reduced by one-third each thousand years thereafter.

This meant that, even if the flow of CO2 were cut off, the climate effects, for better or worse, would persist for that length of time.

It is even worse. It would mean that modest reductions in emission rates would have negligible effects on the peak value of the perturbation-although it would delay its onset.

It would take a massive change in emissions to have an appreciable effect. This creates a policy situation that is almost a crisis one in that any climate change must be treated as hostile even in the absence of specific knowledge and the ability to make accurate climate predictions.

The coupled ocean-atmosphere model has given us better insight into the mechanism of this decay and has greatly reduced its value. For today, we can take it as ranging between 50 and 160 years.

The actual choice is a complicated one. It is an approximation to the true time variation depending on how long is the extent and the shape of the emission curve.

At any rate, it is a big change from the prior 1000-year value and complete alters the policy picture.

Mr. ROHRABACHER. Dr. Nierenberg, would you summarize?

Mr. NIERENBERG. Yes, just one more paragraph just to make this point. Well, this is my main point.

It is to be interpreted in either of two ways, or a combination of both.

On the one hand, those who feel that corrective measures must be taken immediately can now take comfort in the fact that any reasonably applied change in emissions would be reflected in a proportionate reduction in the peak CO2 concentration.

On the other, those who take the more conservative view may argue that one can now safely wait until the climate changes become clearer and more definitely negative before taking action since the effect of the mitigating action would show up in reasonable time.

Thank you.

(The prepared statement and attachments of Mr. Nierenberg follow:)

PREPARED STATEMENT OF WILLIAM A. NIERENBERG, DIRECTOR EMERITUS, SCRIPPS

INSTITUTION OF OCEANOGRAPHY I am grateful for this opportunity to place my views on climate change and modelling before the committee. This testimony is based largely on two documentsProgress and Problems: A Decade of Research on Global Warming, The Bridge (NAE), Vol. 25, No. 2 Summer 1995, pp4-9 and Looking Back Ten Years, IIASA Proceedings, CP-94-9, which I put on the record.

In this prepared statement I summarize what I have written but I do include some additional results that have become available since their publication.

I begin by repeating what I often feel is a necessary prelude to a presentation of the issues. There is no question in my mind that the current anthropological growth of CO2 in the atmosphere is bound to influence the climate. The question is not whether but when, how much and the nature and magnitude of the effects.

The fixing of when has taken an interesting turn. Ten years ago discussions of effects centered around the middle of the next century, often the year 2040. Now, almost universally, climate change effects are normalized at the year 2100, 105 years away from the present. As an example, average sea level rise is projected by current models to be about 30 centimeters, or one foot, at that time. This rate also seems to be consistent with the early results from the TOPEX satellite observations. I should be wanting in this recital if I did not direct attention to the large difference between this result and earlier predictions of order of magnitude larger changes.

The number that surfaces most often in the discussion of climate is the change in the average global surface temperature change. The data for the past one hundred years has been painfully and methodically pieced together and shows rise of about 0.6 degrees Centigrade. Unfortunately, this is the least interesting aspect of climate change. What is crucial is knowledge of the change in the statistical behavior of regional quantities such as rainfall, storm frequency and intensity, flooding, coastal storm surges and so on. By contrast we can visualizee an induced change that increases cloud coverage to the extent that the temperature rises very little but clearly this is a definite climate change.

The weaknesses of the models is most clearly demonstrated by the historical observation that, since the original Charney report of the NRC in 1978, the NAS report of 1983, the IPCC report of 1990 and today, the spread of the temperature rise between the fifteen or so climate models worldwide remains between 1.5 to 4.5 degrees centigrade for an anticipated doubling of atmospheric CO2. This variation between the models is also reflected in lack of agreement in many of the predicted regional climate changes which are so important.

The primary reason for these disagreements is the poorly represented internal atmospheric radiation transfer properties and the overall effect of water, in clouds, cloud formation and water vapor. This is in recognition that water in the form of clouds and vapor is the primary greenhouse gas. Changes in CO2 concentration indirectly influence climate via a feedback effect of the water content of the atmosphere. This has been recognized for years, going back at least to the 1983 NAS report but it is only recently that serious field programs have been undertaken to attempt to formulate a better parametrization of these phenomena. The ARM and CHAMPP programs are in this category.

The other element of time that is crucial is the lifetime of the excess anthropogenic CO2 in the atmosphere. This is a most important number for policy considerations. Here the advent of the coupled ocean-atmosphere model has made definite impact. What is being discussed here is how quickly would the atmosphere relax to a steady state or even its original unimpacted state if the anthropologicall input of CO2 was severely reduced or even curtailed.

The base assumption is that, one way or another, fossil fuel reserves will be exhausted in several hundred years leading to a cutoff in the injection of CO2 into the atmosphere. At the time of the 1983 report the then current calculation in the literature proposed a behavior based on a 1000 thousand year exponential lifetime for the disappearance of the excess CO2 in the atmosphere. That is, that concentration would be reduced by one third each thousand years thereafter. This was serious. This meant that, even if the flow of CO2 were cutoff, the climate effects, for better or worse, would persist for that length of time. It is even worse. It would mean that modest reductions in emission rates would have negligible effects on the peak value of the perturbation (although it would delay its onset). It would take a massive change in emissions to have an appreciable effect. This creates policy situation that is almost a crisis one in that any climate change must be treated as hostile even in the absence of specific knowledge and the ability to make accurate climate change predictions.

The coupled ocean-atmosphere model has given us better insight into the mechanism of this decay and has greatly reduced its value. For today we can take it as ranging between 50 and 160 years. The actual choice is a complicated one and is an approximation to the true time variation depending on how long is the extent and the shape of the emission curve. At any rate, it is big change from the prior 1000 year value and completely alters the policy picture. Ît can be interpreted in either of two ways or combination of both.

On the one hand, those who feel that corrective measures must be taken immediately can now take comfort in the fact that any reasonably applied change in emissions would be reflected in a proportionate reduction in the peak CO2 concentration. On the other, those who take a more conservative view may argue that one can now safely wait until the climate changes become clearer and more defi. nitely negative before taking action since the effect of the mitigating actions would show up in reasonable time.

Taking into account this argument and the currently accepted gestation time of one century, I incline to the latter view. That inclination is strengthened by lack of certainty in the inevitability of all climate changes being harmful. One highly speculative example is based on the recently noted fact that the one degree Fahrenheit increase in temperature is primarily in the night time temperature variation. The daytime temperature is essentially flat. (The models, so far, do not exhibit this behavior.) Some argue that this phenomenon, if continued, would imply better agriculture. I repeat that this is highly speculative but does make the point that all change is not necessarily bad.

The other concern is related to the frequency and severity of storms. There has been considerable arm-waving on this subject with differing conclusions. We now do have a sensitive model calculation (Report No. 139 from the Max-Planck-Institutfur Meteorologie). The authors conclude that, while the intensity of storms will remain the same, their number will decrease. This is still another indication that we have much to learn respecting the effects of anthropologically induced climate change.

There are other important factors that need more field research effort. One is on the nature, distribution and lifetimes of aerosols in the atmosphere. I am assuming that other speakers will discuss this subject.

The other and very difficult area is biota. There is a marked budgetary imbalance in the circulation of carbon between the atmosphere, land and the ocean. It is suspected, with some evidence, that it is caused by the growth of forests, a conclusion opposite to the generally held intuitive one. Until this is numerically fixed a certain degree of uncertainty will remain in model results, particularly in estimating residence times

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