A letter from a reader about Global warming letters: a response

April 4, 2007

In reply to a phalanx of letters (Feb. 14), let me state at the outset: There is general agreement that the climate is currently warming and that the level of the greenhouse gas carbon dioxide is rising, largely attributed to burning of fossil fuels. However, lest anyone ascribe any significance to this correlation, recall that the climate cooled for 35 years (1940-1975) while CO2 increased rapidly. The crucial issue is to establish the main cause of current warming: Is it a natural or anthropogenic (manmade) global warming (AGW)?

Ric Merritt ’74 argues “scientific consensus” on AGW, and cites drift of continents as an example. But this is a classic case: Before the discovery of sea-floor spreading there was a nearly unanimous consensus against it, i.e., that continents do not drift. Just one crucial observation was enough to overthrow the paradigm; the pioneer was Princeton geology professor Harry Hess *32. One could mention Galileo and Einstein, but I don’t want to belabor the point.

Mr. Merritt also makes a common error of logic: In citing retreating glaciers, he confuses consequence of warming with cause. Of course, any kind of warming will melt ice. Glaciers have always receded and grown in response to natural climate cycles. The sea level has risen by 400 feet since the peak of the last ice age, 18,000 years ago – and will continue to rise until the next one.

Professor Nicholas Howe ’93, too, goes with a majority view; but science does not operate by voting – unlike politics. Further, there is no “close correlation” between CO2 and temperature during the past century (see above). Finally, he misunderstands the essence of Karl Popper: A hypothesis (or theory) can never be proven; but it takes only one contrary observation or experiment to falsify it.

Amplifying Nick Davis ’60’s point about climate cycles of the past 150 million years: In my book Unstoppable Global Warming – Every 1,500 Years, I document the overwhelming geological evidence for natural climate cycles, as seen in ice cores, ocean sediments, stalagmites, etc. – and likely caused by the sun. The present warming period may be part of such a cycle, following the “Little Ice Age” of A.D.1400 to 1850.

Kevin Raeder *86 misstates our position: Of course, humans are capable of changing Earth’s climate. But the question always is: How important are such changes when compared to natural ones? This can be answered only by refined observations (see below). I agree with him on many of the action items, like increasing energy efficiency; most make economic sense, irrespective of any climate considerations.

David A. Grossman ’98 is president of an organization with an agenda, the Green Light Group. He is wrong on several points. The general opinion in the 1970s was that the cooling might be the precursor of a coming Ice Age. He quotes from the summary of the U.S. Climate Change Science Program (CCSP), but fails to note that the summary distorts the actual findings of the report (see here Fig. 5.4G, which documents the obvious disagreement between greenhouse models and actual observations). Finally, he warns of dire consequences from warming and claims that “changes are happening faster than expected.” But the just-issued U.N. report on climate science projects reduced changes in temperature and sea-level rise, compared to their last report of 2001. For the record, the global climate has not warmed in the past eight years, according to official data. Recall also that the putative climate effects of CO2 are logarithmic; i.e., they increase ever more slowly as CO2 rises.

Christopher Milly ’78 also quotes from the summary of the CCSP report. I recommend he study the report itself.

Walter Stephan ’52 should be relieved to learn that polar-bear populations are growing – and they obviously survived many previous climate warmings, including the Medieval Warm Period when Greenland supported agriculture.

Professor Raymond Pierrehumbert is a member of a small group of global warming activists that publishes a rather aggressive blog. He labels me a “professional” climate skeptic and – using a less-than-reliable secondary source – implies that I am somehow “tied” to organizations supported by ExxonMobil. Such allegations border on libel and simply show that he has no good scientific arguments to respond to mine. He tries to befuddle the reader with irrelevant references to quantum theory and gravitation, ignoring the fact that the atmosphere is more complex than a physics laboratory. In support of greenhouse models, he claims amplification of warming at the poles; but the Antarctic continent is observed to be cooling. More important, the observed discrepancy between measured and calculated trends with altitude is clear indication of the lack of effectiveness of rising CO2. This “inconvenient truth” is blamed on a “data problem” – which will surprise the many scientists who produced the four independent analyses of both balloon and satellite data used in the CCSP report.

I therefore stand by my original claim that the available evidence shows human influence on global climate change to be of minor importance, when compared to natural causes. I don’t see any good evidence backing the conclusion of the U.N. science panel (IPCC) that the human contribution to current warming is “very likely.” I don’t believe there exists a global-warming problem to be “solved.” Equally, concerns about “saving the climate” are sadly misplaced. I realize that such concerns abound, but trust they will disappear in time.

Professor  emeritus, University of Virginia
Former director of the U.S. Weather Satellite Service
Web site: www.sepp.org
Arlington, Va.

Editor’s note: This is an expanded version of a letter published in the April 4, 2007, issue of PAW. For an essay Singer wrote for Le Monde, please click here.



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