There is no ‘consensus’ on global warming 

By Richard S. Lindzen

According to Al Gore’s new film "An Inconvenient Truth," we’re in for "a planetary emergency": melting ice sheets, huge increases in sea levels, more and stronger hurricanes and invasions of tropical disease, among other cataclysms — unless we change the way we live now.

Bill Clinton has become the latest evangelist for Gore’s gospel, proclaiming that current weather events show that he and Gore were right about global warming, and we are all suffering the consequences of President Bush’s obtuseness on the matter. And why not? Gore assures us that "the debate in the scientific community is over."

That statement, which Gore made in an interview with George Stephanopoulos on ABC, ought to have been followed by an asterisk. What exactly is this debate that Gore is referring to? Is there really a scientific community that is debating all these issues and then somehow agreeing in unison? Far from such a thing being over, it has never been clear to me what this "debate" actually is in the first place.

The media rarely help, of course. When Newsweek featured global warming in a 1988 issue, it was claimed that all scientists agreed. Periodically thereafter it was revealed that although there had been lingering doubts beforehand, now all scientists did indeed agree. Even Gore qualified his statement on ABC only a few minutes after he made it.

So, presumably, not all scientists belong to the "consensus." Yet their research is forced, whether the evidence supports it or not, into Gore’s preferred global-warming template — namely, shrill alarmism. To believe it requires that one ignore the truly inconvenient facts.

To take the issue of rising sea levels, these include: that the Arctic was as warm or warmer in 1940; that icebergs have been known since time immemorial; that the evidence so far suggests that the Greenland ice sheet is actually growing on average. A likely result of all this is increased pressure pushing ice off the coastal perimeter of that island land, which is depicted so ominously in Gore’s movie.

In the absence of factual context, these images are perhaps dire or alarming. They are less so otherwise. Alpine glaciers have been retreating since the early 19th century, and were advancing for several centuries before that. Since about 1970, many of the glaciers have stopped retreating and some are now advancing again. And, frankly, we don’t know why.

The other elements of the global-warming scare scenario are predicated on similar oversights. Malaria, claimed as a byproduct of warming, was once common in Michigan and Siberia and remains common in Siberia — mosquitoes don’t require tropical warmth.

Hurricanes, too, vary on multidecadal time scales; sea-surface temperature is likely to be an important factor. This temperature, itself, varies on multidecadal time scales. Even among those arguing, there is general agreement that we can’t attribute any particular hurricane to global warming.

A general characteristic of Gore’s approach is to assiduously ignore the fact that the earth and its climate are dynamic; they are always changing even without any external forcing. To treat all change as something to fear is bad enough; to do so in order to exploit that fear is much worse. Regardless, these items are clearly not issues over which debate is ended — at least not in terms of the actual science.

A clearer claim as to what debate has ended is provided by the environmental journalist Gregg Easterbrook. He concludes that the scientific community now agrees that significant warming is occurring, and that there is clear evidence of human influences on the climate system.

This is still a most peculiar claim. At some level, it has never been widely contested. Most of the climate community has agreed since 1988 that global mean temperatures have increased on the order of one degree Fahrenheit over the past century, having risen significantly from about 1919 to 1940, decreased between 1940 and the early ’70s, increased again until the ’90s, and remaining essentially flat since 1998.

There is also little disagreement that levels of carbon dioxide in the atmosphere have risen from about 280 ppmv (parts per million by volume) in the 19th century to about 387 ppmv today. Finally, there has been no question whatsoever that carbon dioxide is an infrared absorber (i.e., a greenhouse gas — albeit a minor one), and its increase should theoretically contribute to warming. Indeed, if all else were kept equal, the increase in carbon dioxide should have led to somewhat more warming than has been observed.

The models imply that greenhouse warming should impact atmospheric temperatures more than surface temperatures, and yet satellite data showed no warming in the atmosphere since 1979. The report showed that selective corrections to the atmospheric data could lead to some warming, thus reducing the conflict between observations and models descriptions of what greenhouse warming should look like. That, to me, means the case is still very much open.

So what, then, is one to make of this alleged debate? I would suggest at least three points.

First, nonscientists generally do not want to bother with understanding the science. Claims of consensus relieve policy types, environmental advocates and politicians of any need to do so. Such claims also serve to intimidate the public and even scientists — especially those outside the area of climate dynamics.

Secondly, given that the question of human attribution largely cannot be resolved, its use in promoting visions of disaster constitutes nothing so much as a bait-and-switch scam. That is an inauspicious beginning to what Gore claims is not a political issue but a "moral" crusade.

Lastly, there is a clear attempt to establish truth not by scientific methods but by perpetual repetition. An earlier attempt at this was accompanied by tragedy. Perhaps Marx was right. This time around we may have farce — if we’re lucky.

Richard Lindzen is the Alfred P. Sloan Professor of Atmospheric Science at MIT. Reprinted from The Wall Street Journal © 2006 Dow Jones & Company. All rights reserved.

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