Sunday, May 08, 2005

The Climate of Man

If you still have any doubts about the scientific consensus about man-made global warming, or what the US is (not) doing to stave it off, the New Yorker has published a three-part article by Elizabeth Kolbert in its ANNALS OF SCIENCE section. (The article is no longer available through the New Yorker site, but has been published as a book, Field Notes from a Catastrophe .)

In typical New Yorker style, it tells you more than you realized you wanted to know. Here's a small sample:

The National Academy of Sciences undertook its first rigorous study of global warming in 1979. At that point, climate modelling was still in its infancy, and only a few groups, one led by Syukuro Manabe, at the National Oceanic and Atmospheric Administration, and another by James Hansen, at NASA’s Goddard Institute for Space Studies, had considered in any detail the effects of adding carbon dioxide to the atmosphere. Still, the results of their work were alarming enough that President Jimmy Carter called on the Academy to investigate. A nine-member panel was appointed, led by the distinguished meteorologist Jule Charney, of M.I.T.

The Ad Hoc Study Group on Carbon Dioxide and Climate, or the Charney panel, as it became known, met for five days at the National Academy of Sciences’ summer study center, in Woods Hole, Massachusetts. Its conclusions were unequivocal. Panel members had looked for flaws in the modellers’ work but had been unable to find any. 'If carbon dioxide continues to increase, the study group finds no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible,' the scientists wrote. For a doubling of CO2 from pre-industrial levels, they put the likely global temperature rise at between two and a half and eight degrees Fahrenheit. The panel members weren’t sure how long it would take for changes already set in motion to become manifest, mainly because the climate system has a built-in time delay. It could take 'several decades,' they noted. For this reason, what might seem like the most conservative approach—waiting for evidence of warming in order to assess the models’ accuracy—actually amounted to the riskiest possible strategy: 'We may not be given a warning until the CO2 loading is such that an appreciable climate change is inevitable.'

It is now twenty-five years since the Charney panel issued its report, and, in that period, Americans have been alerted to the dangers of global warming so many times that volumes have been written just on the history of efforts to draw attention to the problem. (The National Academy of Sciences alone has issued nearly two hundred reports on global warming; the most recent, 'Radiative Forcing of Climate Change,' was published just last month.) During this same period, worldwide carbon-dioxide emissions have continued to increase, from five billion metric tons a year to seven billion, and the earth’s temperature, much as predicted by Manabe’s and Hansen’s models, has steadily risen. The year 1990 was the warmest year on record until 1991, which was equally hot. Almost every subsequent year has been warmer still. The year 1998 ranks as the hottest year since the instrumental temperature record began, but it is closely followed by 2002 and 2003, which are tied for second; 2001, which is third; and 2004, which is fourth. Since climate is innately changeable, it’s difficult to say when, exactly, in this sequence natural variation could be ruled out as the sole cause. The American Geophysical Union, one of the nation’s largest and most respected scientific organizations, decided in 2003 that the matter had been settled. At the group’s annual meeting that year, it issued a consensus statement declaring, 'Natural influences cannot explain the rapid increase in global near-surface temperatures.' As best as can be determined, the world is now warmer than it has been at any point in the last two millennia, and, if current trends continue, by the end of the century it will likely be hotter than at any point in the last two million years.

In the same way that global warming has gradually ceased to be merely a theory, so, too, its impacts are no longer just hypothetical. Nearly every major glacier in the world is shrinking; those in Glacier National Park are retreating so quickly it has been estimated that they will vanish entirely by 2030. The oceans are becoming not just warmer but more acidic; the difference between day and nighttime temperatures is diminishing; animals are shifting their ranges poleward; and plants are blooming days, and in some cases weeks, earlier than they used to. These are the warning signs that the Charney panel cautioned against waiting for, and while in many parts of the globe they are still subtle enough to be overlooked, in others they can no longer be ignored. As it happens, the most dramatic changes are occurring in those places, like Shishmaref, where the fewest people tend to live. This disproportionate effect of global warming in the far north was also predicted by early climate models, which forecast, in column after column of FORTRAN-generated figures, what today can be measured and observed directly: the Arctic is melting.

Read it and weep.

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