Warming debate: Scene 1, take 2

Second of two parts  

IF THERE'S anything climate-change crusaders are adamant about, it is that the science of the matter is settled. That greenhouse gases emitted through human activity are causing the planet to warm dangerously, they say, is an established fact; only a charlatan would claim otherwise. In the worlds of Al Gore, America's leading global warming apostle:  

"There's no more debate. We face a planetary emergency. . . . There is no more scientific debate among serious people who've looked at the evidence."  

But as with other claims Gore has made over the years ("I took the initiative in creating the Internet"), this one doesn't mesh with reality.  

Scientists and other "serious people" who question the global warming disaster narrative are not hard to find. Last year 60 of them sent a letter to Prime Minister Stephen Harper of Canada, urging him to undertake "a proper assessment of recent developments in climate science" and disputing the contention that "a climate catastrophe is looming and humanity is the cause." The letter cautioned that  

"observational evidence does not support today's computer climate models"

and warned that since the study of climate change is relatively new,  

"it may be many years yet before we properly understand the earth's climate system."  

Among those signing the letter to Harper were Fred Singer, the former director of the US Weather Satellite Service; Ian Clark, hydrogeology and paleoclimatology specialist at the University of Ottawa; Hendrik Tennekes, the former director of research at the Royal Netherlands Meteorological Institute; physicist Freeman Dyson of the Institute for Advanced Studies in Princeton; the University of Alabama's Roy Spencer, formerly senior scientist in climate studies at NASA's Marshall Space Flight Center in Huntsville, Ala., plus 55 other specialists in climate science and related disciplines.  

The debate among scientists is over?  

NASA administrator Michael Griffin told National Public Radio in May that while the general trend of global warming exists, that doesn't make it "a problem we must wrestle with." To insist that any change in climate must be bad news  

"is to assume that the . . . earth's climate today is the optimal climate, the best climate that we could have."  

The planet's temperature has been fluctuating for millennia, he added.

"I don't think it's within the power of human beings to assure that the climate does not change."  

In 2003, environmental scientists Dennis Bray and Hans von Storch surveyed 530 of their peers in 27 countries on topics related to global warming. One question asked:  

"To what extent do you agree or disagree that climate change is mostly the result of anthropogenic causes?"  

On a scale of 1 (strongly agree) to 7 (strongly disagree), the average score was 3.62, reflecting no clear consensus.  

Asked whether abrupt climate changes will wreak devastation in some areas of the world, the percentage of scientists strongly agreeing (9.1) was nearly identical to the percentage strongly disagreeing (9.0). Another question asked: To what degree might global warming prove beneficial for some societies? A striking 34 percent of the scientists answered 1 or 2 (a great degree of benefit); just 8.3 percent answered 6 or 7 (very little/no benefit).  

Plainly, the science isn't settled. It changes all the time.  

Take the latest report of the Intergovernmental Panel on Climate Change. Unlike its previous report in 2001, which foresaw a possible rise in sea levels over the next century of around 3 feet, the new report cuts that figure in half, to about 17 inches. Why the revision? "Mainly because of improved information," the IPCC notes in the fine print. It goes on to note that even its latest estimate involves some guesswork: "Understanding of these effects is too limited to assess their likelihood." The science is getting better, but it's far from settled.  

Or take the discovery this month that 1934, not 1998, was the hottest year in the continental United States since record-keeping began. NASA's Goddard Institute for Space Studies quietly changed its ranking after a Canadian statistician discovered an error in the official calculations. Under the new data, five of the 10 hottest US years on record occurred before 1940; three were in the past decade.  

Climate scientists are still trying to get the basics right. The latest issue of Science magazine notes that many researchers are only beginning to factor the planet's natural climate variations into their calculations. "Until now," reports Science, "climate forecasters who worry about what greenhouse gases could be doing to climate have ignored what's happening naturally. . . . In this issue, researchers take their first stab at forecasting climate a decade ahead with current conditions in mind."  

Their first stab, please note, not their last. The science of climate change is still young and unsettled. Years of trial and error are still to come. Al Gore notwithstanding, the debate is hardly over.