|ON GLOBAL WARMING
Special to the Cornwall Alliance, March 16, 2007
By Richard S. Lindzen, Alfred P. Sloan Professor of Atmospheric Sciences, Massachusetts Institute of Technology
original text: http://www.sepp.org/
I am frequently asked to describe my experiences as a contrarian about global warming. I still find the request somewhat annoying, and in this piece I would like to explain why. For starters, to be a contrarian generally implies an automatic tendency to go against popular wisdom. That is not my position.
What in the world does it really mean to be a contrarian on the issue of global warming? On an issue where virtually all popular depictions depend on long chains of uncertain connections, support for all these linkages would constitute more a religious faith than a scientific position. On the other hand, where the elements of the picture do deal with relatively basic issues, there is, in fact, little disagreement. Some examples may help clarify the situation.
For instance, there is little argument that levels of C02 in the atmosphere have risen from 315 ppmv when we began systematic measurement in 1958 to about 380 ppmv today. There is also relatively little argument that preindustrial levels were about 280 ppmv. There is no disagreement that C02 is a gas with important absorption bands in the infrared.
There is agreement that at the level of fractions of a degree, the earths global mean temperature is always varying, and there is widespread agreement (though with appreciably greater uncertainty) that over the past century there has been net warming of between 0.50 and 0.75C (depending on which analysis one uses). This warming has, as far as anyone can tell, been irregular, with warming between 1920 and 1940, modest cooling between about 1940 and the mid 70's, warming between about 1976 and the early nineties, and little of either since.
Even the UN's Intergovernmental Panel on Climate Change acknowledges that greenhouse forcing is currently about three quarters of what one would expect from a doubling of C02, and yet we have seen much less warming at the surface than the models project - even with models that have oceans which are supposed to delay the response.
Here the argument amounts to one between those like me, who think that the most likely reason for the discrepancy is that models are exaggerating the response, and those who think the models are correct, but that aerosols have cancelled much of the warming. However, even the IPCC acknowledges that our confidence in the aerosol cooling is low.
Agreement goes even further: there is general agreement that the famous blanket picture of the greenhouse effect that Gore likes to present is, in fact, misleadingly wrong. Rather, the real greenhouse climate effect requires most warming to occur in the middle of the tropical troposphere (cooling at the surface is mainly by motion systems, with the heat deposited in the middle of the troposphere where it is then radiated to space), and as a recent report of the National Research Council notes, warming trends at this level in the tropics appears to actually be even smaller than at the surface.
For me personally, I find that the low climate sensitivity is consistent with my research on cloud feedbacks and other matters, but when it comes to current research one doesn't normally seek general agreement.
So where is there significant disagreement?
The main focus of disagreement has remained much the same since I first went public with my objections to catastrophic claims in 1988. (It is sobering to realize how long we have been told by environmental groups like the Union of Concerned Scientists that the end of the world as we know it is imminent due to global warming.) At that time, I felt confident, on the basis of my own research over the previous decade or more, that our knowledge did'nt warrant these claims.
Given the long term nature of climate, it should not be surprising that there is little reason to change this position. Nevertheless, it has, since the 80's, led to an important disagreement with some of my colleagues over whether our present limited knowledge warrants deep concern or not. I, personally, don't think so, but I respect my colleagues right to feel otherwise. This difference is distinct from the issue of whether concern is tantamount to feeling that specific actions are warranted. Most of my colleagues would agree, for example, that Kyoto is merely symbolic with little potential for affecting climate. Some favor other approaches, but I think there is widespread acknowledgment that with presently known or anticipated technology there is little that one can do to significantly cut greenhouse
gas levels, and even less that one can do to significantly reduce radiative forcing by greenhouse gases (which, in the case of C02, goes up much more slowly than the level of C02 itself).
There are, of course, some who feel that warming concerns are a good excuse for implementing their pet energy policies. Here, I share with the late Roger Revelle (whom Gore points to as his mentor in this area) the view that current evidence does not warrant any drastic actions that cannot be justified independently of climate concerns.
Given my views, I am happy to be at an institution like MIT. At least most people at MIT are sufficiently technically savvy to appreciate the arguments involved with this issue. In the world at large, the situation is certainly different. No scientific issue has likely ever been as politicized as this one. Global warming has for about 20 years been a major focus of environmental advocacy groups and their political allies. In the last two years, they have greatly expanded their efforts to spread alarm to the public at large, including elementary school children, who lack any ability to understand the issue and are apparently suffering an appreciable degree of anxiety.
In any marketing effort, it is useful to offer the objects of the propaganda something that they value. In the present instance, they are offered at least two such benefits. First, they are given a sense of virtue: simply by changing light bulbs or (for the wealthier) buying a Prius or even by paying some outfit an indulgence to cancel their carbon footprint, they are made to feel that they are saving the world. Second, their intellectual insecurity when confronting such a complex issue is relieved by being told that all scientists agree with whatever propaganda they are fed. Under the circumstances, they are made to feel that in going along with the propaganda, they are displaying intelligence, and acquiring the right to consider anyone who does not as being either stupid or hopelessly corrupt.
Thus, the existence of questions about the validity of the global warming alarmism threatens both their virtue and their intelligence, and it should not be surprising that the response to such threats can be emotionally intense.
However, judging from my email, a great many people are beginning to resent being exploited in this manner. I fully expect that this latter group will eventually be vindicated, and that alarm over global warming will go the way of Y2K and the Club of Rome forecasts for hunger (not to mention the fears over global cooling of just 30 years ago).