The major advances in our thinking relative to global warming in these last ten years have been largely made outside the model environment. They have been accomplished via field measurements, some of which have been very ingenious. Among them are the ice core work in the Antarctic (now also in Greenland), the measurement of aerosol concentrations (much more is needed), the direct measurement of the flow of CO2 into the ocean from the atmosphere, vertical temperature probes into the Canadian Shield and the now continuing measurement of the surface temperature at the earth's surface via satellite observations.

The latter series of measurements now cover a slightly larger time span than 10 years to the present. They show no change in average surface temperature over that period of time which is in contradiction to the behavior of the ground station averages. This difference has to be resolved. The measurements, in a sense, cost nothing. They are a byproduct of measurements on spectral emission lines of molecular oxygen.

The results from the bore holes in the Canadian Shield present still another view on what may be happening. The authors used old and new vertical logging temperature data from abandoned oil prospecting holes to calculate the surface temperature backwards in time for a few thousand years from its diffusive penetration into the earth's surface. The analysis is complicated but they do indeed observe a recent significant rise that, however, follows a minimum in the last century. The effect is more pronounced in Eastern Canada than in the west. This result is somewhat comforting because all models, from the simplest to the most complex, predict increases in the polar regions significantly larger than the average and particularly the equatorial values. The ground station observations do not show this difference and this had been held to be still another model deficiency.

Included in this category of recent advances in understanding the set of phenomena are the aerosols and the changes in visualization of the carbon cycle that were mentioned earlier. These subjects are by no means closed. (Remainder of sentence deleted.)

Still, for the time being, the giant computer models offer the only apparent road to estimating regional climate changes due to perturbations, man made or natural. One weakness, that of the effect of changes in atmospheric water content, is being attacked by means of a major field program in the United States, ARM (Atmospheric Radiation Measurements). It is a large complex of instruments that eventually is to be established in a variety of locations to measure the radiation patterns under the normal variety of weather conditions. Again we must wait and be patient.

A totally different set of problems are now being examined that go to the mathematical foundations of the equations that are fed into the computers. These equations are composed of many independent variables connected in a highly non-linear environment. From the famous work of Lorenz on the similar equations for predicting weather we already know that there are problems with the solutions to these equations. But we are also aware of the possible chaotic behavior of coupled non-linear equations. Just what that means in this application is not at all clear. We can say that we do not know to what extent the system is predictable.

What is clear is that solutions often tend to drift and artificial boundary conditions have to be employed to stabilize the solutions. When the coupled ocean model was introduced, it was found necessary to use altered values for the wind stress on the ocean surface to obtain non-drifting solutions. As an aside, there is a very difficult problem to overcome in that the time scales for the ocean are far longer

7 a) Lauchenbruch, A.H. and Marshall, B.V. 1986. Changing Climate: geothermal evidence from permafrost in the Alskan Arctic. Science, 234:689-696.

b) Lewis, TJ. (Editor) 1992. Climatic change inferred from underground temperatures. Special issuc, Global and Planctary Change 6:71-281.

8 Spencer, Roy W. and Christy, John R. Precise Monitoring of Global Temperature Trends from Satellites. Science 247:1558-1562 30 Mar 1990.

than those for the atmosphere and, conversely, the length scales for the ocean are far shorter than those for the atmosphere. A good boundary match is very difficult to achieve. Withal, the computer models achieve a surprisingly good picture of the earth's climate. But this method of "tuning" the models to obtain today's climate is probably not adequate to evaluate changes in climate due to perturbations such as those due to the anthropogenic introduction of greenhouse gases.

This extra detail on models is intended to advance to the next topic which is that of mitigation. To have a successful mitigation program it is necessary to be assured with certainty that the program carries no harmful or unacceptable side effects. To put forward a general statement -- although a mitigation procedure is an intended perturbation unlike that of global warming due to CO2 emissions, it is, nevertheless a perturbation that has to be analyzed with the best analytic tools available, namely the GCM's. However, from the preceding discussion, we can only be sure that we cannot foretell the regional climate consequences with any degree of reliability and, we may, in fact, unicash a whole scries of "unintended consequences", to intentionally borrow a term from the economists. This makes the entire concept of mitigation a precarious one.

This thesis can be made a bit clearer by examining a popular example, that of planting large expanses of trees sufficient in area to take up the increase in CO2 via the excess of photosynthesis over respiration. It is feasible and has certain additional attractiveness if the forests are systematically harvested for fuel, particularly in the form of methyl alcohol. However, there have been several analyses of this stratagem indicating that the change in albedo that would result would just about balance the resultant decrease in greenhouse forcing due to the uptake in CO2. This would appear to be harmless enough except that the reforesting would be concentrated in specific areas of the globe and, while the CO2 forcing is, in some sense, uniform over the globe, the change in albedo would be highly variable over the surface. The asymmetry produced would clearly have variable regional climate changes despite the maintenance of a constant average global surface temperature.

There is another, somewhat more subtle, example of the difficulty in achieving a proper mitigating action. One of the odd and previously unnoted features of the 0.5 degree rise in surface temperatures in the last one hundred years is that the rise has been manifested in the night time temperature averages for part of the record and part of the globe. The day time temperature averages show no change. The GCM models do not show this effect. The implication is that the use of artificially introduced stratospheric aerosols, another popular proposal, would not achieve the same asymmetry and, again, the mitigative effect would not be neutral.

There is a curious parallel to this discussion of the natural phenomenon of global warming in the approach that economic modelers take. After all, one half the problem of global warming is predicting the economic behavior of the peoples of the planet for the next one hundred years. The equations used by the economists have the same ill-natured behavior as the climate ones in being of many dependent variables and highly non-linear. They suffer the same predictive weaknesses and the combination of the two does not engender great optimism.

While this is a sobering review of the scientific status of a maior world problem, it by no means implies that we are helpless in dealing with it. Complex problems of this nature are never "solved" in the simple mathematical sense. Rather, we deal with them as best we can in light of current and increasing knowledge. Without waiting for a clearer signal on global warming to emerge, the nations of the world have agreed at Geneva to recognize that a grave potential problem exists. The next step is the development of an accepted political and economic pattern of reduction of the use of carbon fuels. We have already noted that the arrival of the anticipated coupled ocean-atmosphere climate models have yielded clearer insight into the lifetimes of the airborne fraction of anthropogenic CO2. These new numbers support the value of relatively modest reductions in consumption but also relieve to a large degree the time urgency of action and permit a "tailoring" of response to observed effects.

Analysis has already reduced the implied impact of sea level rise. Similarly, the analysis in the Academy report of anticipated agricultural effects in the United States for the next fifty years or so shows a zero change in balance between fertilization induced by the increased CO2 and decreased rainfall. Refinements in the intervening years show no reason to change this conclusion. Concomitant analyses can and should be made for other regions of the world.

It is instructive, then, to bypass the complexities of both the climate and economic models by the following argument. We look back and accept the the rate of exponential growth of atmospheric CO2 for the last one hundred years as a given and use it to predict the future growth at the same rate. Since we know that the greenhouse effect of CO2 will increase only logarithmically with the concentration, we would expect an increase in global temperature in the next one hundred years of the same amount as for the last one hundred years namely 0.6 degrees centigrade, assuming that the temperature rise was indeed due to the rise in CO2. This is conservative reasoning but unfortunately tells us nothing of the regional climate changes. This also predicts something less than doubling of the CO2 concentration in that period.

There is no reason to believe that we are at the end of surprises in this very complicated set of phenomena. At this very time we are being exposed to two very radical concepts. The first is derived from the very recent measurements on the Greenland ice cores. This is a natural sequence to the researches on the Antarctic cores and the wealth of information that ensued. The Greenland cores are more informative because the greater precipitation yields time resolution of the order of one year. The extraordinary result, which is now widely disseminated, is that the earth's climate, as revealed by the cores, was extremely variable on nearly a year to year basis with abrupt changes in average temperature of the order of several degrees centigrade. This pattern abruptly ceased about ten thousand years ago and the temperature (and thus presumably the climate) has remained relatively quiet since. There are several implications or one can more properly speak of surmises. The one is that we are, and have been for several thousand years, in an abnormal climatic state. Another is that we are liable to leave this state and return to the more "normal" one of constant fluctuation at any tine. The weakness of this argument is that the reccord would only apply regionally, perhaps only to the North Atlantic. But then that also limits the geographical applicability of the temperature record.

The difficult part, if these observations hold up, is that our modcls give no indication of the existence of an earth with this kind of fluctuating climate. While there has been much talk and some examples of an earth with more than one "stable" climate, mostly in connection with attempts to explain the ice ages, they have not been very convincing The explanation may be straightforward and more comforting. This fluctuating behavior occurred during a period of glacier recession. There is no reason to believe that the glaciers receded uniformly and it is more likely that they alternated in receding from year to year. If so, Greenland would be subject to frequent reversals of winds that are symptomatic or causal of abrupt climate changes. Examination of the particles trapped in the cores may tell the story".

Questions have also recently arisen in another area. That concerns the source of the rise in CO2 concentration as measured by Keeling. By ignoring the seemingly close correlation between the shape of the known CO2 emissions and the Keeling curve and starting ab initio, the startling conclusion can be reached that the anthropogenic component is only part of the rise and the remainder is due to shifts in the much larger natural reservoirs and fluxes. There is some debate swirling around this result but, if it too holds up, then the mitigation and adaptation issues change radically. The problem does not necessarily go away because the changes we may face are not man induced. They may become even more serious. It is one thing to plan mitigation against man's intervention into the environment. It is another to discuss mitigation against natural global climate change.

9 Lindzen, Richard, Private Communication, Sept.,1993

Climate change is a fascinating and enjoyable topic when it is drawn away from policy and political considerations. The history of vineyards in Great Britain, the disappearance of Indian complexes in the United States Southwest, the abandonment of farming in the deserts in Peru and many other examples have induced great intellectual curiosity, research and entertainment. I feel that I should add a brand new one drawn from the observation that the earth had a highly variable climate until about ten thousand years ago. This change coincides closely with man's development of an agricultural basis for existence. Until that time there is no archaeological evidence of any agricultural activity. Human life was that of hunting and gathering. We could surmise that only when the year to year climate remained reasonably stable in a given area that it became possible to experiment, to select and to draw reasonable return from the efforts.

November 7, 1994

Mr. ROHRABACHER. Just to let you know, and I respect each and every one of the panelists today, I mentioned earlier that I am a journalist by profession.

We were taught as journalists to put the most important item right up front. That is the lead of the story. Now in the academic world it is just the opposite, as you lead up to your most important point.

[Laughter.]

Mr. ROHRABACHER. When it comes to situations like this where we have about five minutes, I know how frustrating it must be to be trained in the academic profession and not be able to lead up to your point because, just as you get there, you have run out of time. So we will try to accommodate you, but if we could try to keep it as close to five minutes as possible so we can get some dialogue, and you can then actually expand upon your points.

Mr. NIERENBERG. Mr. Chairman, can I respond very briefly to that? I have a special problem. I understand that very well.

You see, several of the speakers now have spoken about hundreds, and even millennia, you see, in terms of this decay period. This is a very crucial policy issue, and I did not want to respond the same way just by saying it is 100 years and letting it go at that.

That is the crucial issue as far as you are concerned, you the Congress.

Mr. ROHRABACHER. Thank you, Doctor, we will be discussing that.

Mr. Gardiner?

STATEMENT OF DAVID GARDINER, ASSISTANT ADMINISTRATOR, OFFICE OF POLICY, PLANNING AND EVALUATION, U.S. ENVIRONMENTAL PROTECTION AGENCY

Mr. GARDINER. Thank you, Mr. Chairman, for the opportunity to be here to discuss the EPA report entitled The Probability of Sea Level Rise, which we released on October 27th, 1995.

This report provides estimates of the impact of climate change on coastline seal level elevations and is the first to attach not "predictions" but "probabilities" to different projections of sea level rise. This report builds on previous scientific studies, reconfirming the likely risk of sea level rise and reinforcing our concerns regarding the resulting environmental and economic impacts.

It also projects that global warming will worsen sea level rise significantly unless actions are taken to avoid it.

Let me say at the outset that we believe there is a strong scientific consensus on the following facts:

First, the sea is rising now, a trend that is confirmed by measurement data from the last 100 years.

Second, the sea will continue to rise over the next century and beyond.

Third, climate models are getting more accurate over time and are important for understanding future potential climate changes. Fourth, there is a growing scientific consensus that human-induced climate change is a reality.

And fifth, the uncertainties surrounding our projections of sea level rise are narrowing.