FOR nations to use climatic history as a guide in planning for the future is to court disaster. The potential for disruptive man-made climate change is now so clear that the past is an unreliable guide. So warns the World Meteorological Organization in a series of press conferences it has been holding around the world. WMO, a United Nations agency, is publicizing release of an extensive study of the potential economic, geographical, meteorological, and social impacts of such climate change. This is a warning to take very seriously. It's easy to dismiss it as just another climatic ``alarm.'' But that would be misguided.
Scientific understanding of possible man-made climate change has been growing slowly over several decades. Early signs that such change may actually be occurring remain obscure. Thus there is a continuing series of reports expressing concern about a climatic threat that is not yet obvious to most people. This is in no sense crying ``wolf.'' It is, rather, a growing and informed awareness that such ``climatic problems will be part of people's lives over the next century,'' as Swedish meteorologist Bert Bolin said at the recent WMO press conference in Stockholm.
The WMO study is specifically concerned with the warming influence of the continuing buildup of heat-trapping gases in the atmosphere - the so-called greenhouse effect. Greenhouse gases include carbon dioxide released by burning fossil fuels, methane associated with the spread of agriculture, and the chlorofluorocarbons that also destroy stratospheric ozone.
Computer simulations indicate that this buildup will raise Earth's global average temperature several degrees over the next 50 to 75 years. In a review of present knowledge published in Science April 15, V. Ramanathan of the University of Chicago pointed out that ``the predicted changes, during the next decades, could far exceed the natural climate variations in historical times.''
Among the possible disruptive consequences of greenhouse warming are rising sea levels as icecaps melt, with flooding of coastal areas and shifts in precipitation patterns that could dry out some important farmlands. ``We are entering a new phase,'' said Bolin, adding, ``we told the world what scientists believe will be the case.... Now nations and politicians must start to think about the problems.''
Such thinking could well include planning to restrict development in coastal areas likely to be flooded a few decades hence. It could include more extensive research to develop drought-tolerant crops and dry farming techniques for now fertile areas that may dry out in the future. It could, in short, factor possible consequences of greenhouse warming into all land-use planning.
As Bolin said, the scientists have made the danger clear. Now it's time to take their warning seriously.
A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.