Time to cool global greenhouse

THANKS partly to the severe North American drought, the greenhouse climate threat hit front pages and prime-time TV news recently. But, having raised the alarm about heat-trapping air pollution, the news media quickly shifted their attention elsewhere. In fact, news interest faded so fast there has been little reporting of the conclusions of the global conference on the subject that Canada played host to in Toronto during the last four days of June. Yet those conclusions go to the core of the perplexing question of how seriously to take an environmental threat that is ill-defined and will take decades to develop fully.

The technical discussions revealed, once again, that scientists cannot yet foretell just what a global average warming of one to several degrees will mean environmentally or how fast it is likely to develop. But they also emphasized that we can't wait for clearer vision. We must begin now to curb the accumulation of heat-trapping pollution.

This represents a watershed in scientific opinion on the subject. Greenhouse researcher Stephen H. Schneider of the National Center for Atmospheric Research in Boulder, Colo., observed, ``There has been a radical increase in the number of scientists who think we should do something about the problem,'' according to Chemical and Engineering News.

The greenhouse gases include carbon dioxide (CO2) released in burning fossil fuels and wood from forest destruction; methane from rice paddies, livestock, and other aspects of farming; chlorofluorocarbons (which also destroy the ozone layer); and some other man-made pollutants. Scientists were originally concerned mainly about CO2. But they now realize that the other gases, taken together, have a comparable warming effect. Thus the climate-warming pollution is building up faster than most experts had expected even half a decade ago.

Therefore, in spite of the scientists' uncertainties about the possible climatic effects, the conference urged nations to begin now to develop cooperative international plans to cut back on the pollution. Specifically, it recommends cutting CO2 emissions by 50 percent or more from current levels in the long run. As a first stage, it urges a 20 percent cut by the year 2005. It also urges steps to reduce emission of other greenhouse gases.

This is an immense challenge. It speaks directly to national and international energy use and development which now are raising the emissions of greenhouse gases. To cut back those emissions would require a radical rethinking of the global economy. That includes special help for developing nations, which cannot pollute their way to wealth as did the present industrial countries.

To adopt these objectives or whatever goals are realistic and establish a workable strategy to meet them will take long and painful international discussion. This is an effort in which the industrial countries - especially the United States, which is the worst greenhouse polluter - should take the lead.

A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.