Cold Comfort for 'Global Warming'

Last week's dramatic demise of the Larsen B ice shelf in Antarctica has been embraced by environmentalists and commentators who warn of human-induced "global warming." After all, the ice shelf was 200 meters thick, with a surface area three times the size of Hong Kong. Around 500 billion tons of ice collapsed in less than a month. How could President Bush ignore such evidence of our guilt with regard to climate change?

An ice shelf is a floating extension of the continental ice that covers the landmass of Antarctica. Larsen B was one of five shelves that have been monitored by scientists. The U.S.-based National Snow and Ice Data Center described its break-up as "the largest single event in a series of retreats by ice shelves in the peninsula over the last 30 years."

One worry can be dismissed immediately: Having been a shelf -- a floating part of an ice sheet, rather than over land -- it does not raise sea levels upon melting. Yet the collapse has proved to be a perfect natural disaster for the "Apocalypse Now" school of journalism. It is now perfectly clear that we are all doomed and that this is the wake-up call for urgent action on greenhouse gas emissions, automobiles, industry, and virtually everything else to do with economic growth.

Unfortunately, the story isn't quite so straightforward. Antarctica illustrates the complexities behind understanding climate change, and it provides little support for a simplistic myth of human-induced "global warming." In fact this scare is reminiscent of a much-hyped New York Times story last year that "leads" of open water in ice fields near the North Pole filled cruise passengers with a "sense of alarm" about impending climate disasters. But icebreakers are always searching for "leads" to make their way through the ice, and after a long summer of 24-hour days it is not unusual to find them all over the place, especially after strong winds break up the winter ice. Sorry, the North Pole isn't disappearing -- and neither is the South Pole.

Research on the West Antarctic Ice Sheet has shown precisely the opposite trend seen at Larsen B, namely that this ice sheet may be getting thicker, not thinner. Most scientists think that the sheet has probably been retreating, spasmodically, for around the last 10,000 years, but instead of the rate accelerating in recent years, it now appears to have halted its retreat. There is evidence that the ice sheet in the Ross Sea area is growing by as much as 26.8 gigatons per year, particularly on a part of the ice sheet known as Stream C.

This demonstrates the innate complexity of Antarctica as a continent. In reality, it has many "climates," and many geomorphological and glaciological regimes. It does not respond to change, whatever the direction, in a single, unitary fashion. Geomorphological and ecological trends are thus very difficult to interpret in a linear way.

One trend has been toward a colder climate. Over the last 50 years, the temperatures in the interior appear to have been falling. University of Illinois researchers have reported, in Nature, on temperature records covering a broad area of Antarctica. Their measurements show "a net cooling on the Antarctic continent between 1966 and 2000." Indeed, some regions, like the McMurdo Dry Valleys, the largest ice-free area, appear to have cooled between 1986 and 1999 by as much as two degrees centigrade per decade. As the researchers wryly comment, "Continental Antarctic cooling, especially the seasonality of cooling, poses challenges to models of climate and ecosystem change."

At the same time that parts of the continent are cooling, it's hardly surprising to see some ice melting. We are currently emerging -- granted in a somewhat jerky fashion -- out of the Little Ice Age that ended around 1880. It's to be expected that some parts of Antarctica like Larsen B are retreating. Yet we seem to be shocked at this perfectly natural event. When will we recognize the basic truth that change, both evolutionary and catastrophic, is the norm on our ever-restless planet?

Extreme environmentalists and sensationalist journalists pretend that every environmental event is of our own making. If only. We don't have that much control over Mother Nature. While we've been busy gabbing about global warming, the planet may be moving in the opposite direction.

Our current interglacial period is already 10,000 years old. No interglacial period during the last half-million years has persisted for more than 12,000 years. Most have had life spans of only 10,000 years or less. Statistically, therefore, we are due to slither into the next glacial period.

Despite a short-term rise in temperature of around 0.6 degrees centigrade over the last 150 years, the long-term temperature trend remains, overall, one of cooling. It may not be too long, therefore, before we see the ice spreading again. At worst, the emission of greenhouse gases is only likely to produce a super interglacial period; at worst, withdrawing gases might help to speed the descent into the next glacial period. And what would you prefer, a warmer or a colder world?

Mr. Stott, emeritus professor of biogeography at London University, is co-author of "Political Ecology: Science, Myth and Power" (Oxford University Press, 2000).

Updated March 25, 2002