Global warming or hot air?

IF WE DO nothing, global warming will eventually transform the nation's midsection into a desert, and put many of our coastal cities under water--at least that is the scenario proffered by environmental groups and the media.

Recent studies show, however, that a potentially dangerous cooling trend has been under way for most of the earth's history: there was five to ten times more carbon dioxide in the atmosphere one hundred million years ago, and the average temperature was 9[degrees]F. to 18[degrees]F. warmer than now. Fred Singer, a professor of environmental sciences at the University of Virginia, suggests that the "climate optimum" occurred around 1100 A.D., when Greenland was indeed green, and the area the Vikings called Vinland (thought to be Labrador) was warm enough for grape growing. The 0.9[degrees]F. rise in average global temperature recorded since 1880 may simply be a return to normal following the "Little Ice Age" of 1600 to 1860.

In any event, it's not at all clear that man is responsible for the warming trend. Although carbon dioxide accounts for about half of all greenhouse gases, human activity accounts for only 5 per cent of all carbon dioxide. If economic activity caused global warming, the temperature rise should be accelerating, but it isn't. A recent study by Kent Jeffries of the Competitive Enterprise Institute shows that almost all warming in this century took place in the 1920s and 1930s, long before most of the emission of trace gases by humans. The earth cooled off from 1940 to the mid Seventies, and got hotter from 1975 to 1980. Despite the recent string of abnormally warm years, the Eighties as a whole exhibited no discernible temperature trend.

Systematic global measurements suggest that any rise in temperature is occurring mainly at night, in the winter, and in the northern hemisphere. If this pattern persists it will mean longer growing seasons, fewer frosts, but no increase in the likelihood of drought.

To the chagrin of environmentalsits, the scientific community has largely retracted its earlier apocalyptic warnings. During the record heat of 1988 theorists were predicting that a doubling of carbon dioxide would raise global temperature by 8.1[degrees]F. to 10.8[degrees]F. The scientific consensus is now below 2.7[degrees]F. Polar ice caps, far from melting, appear to be growing. So while most climatologists in 1980 were predicting a thirty-foot rise in future sea levels, that estimate had fallen to three to five feet by 1988, and to 12 inches in the current worst-case forecast, according to Jeffries. The dearth of hard evidence attesting to human culpability has not deterred those who think a little suffering is in order. A UN panel has urged international action to reduce greenhouse gases, and several bills in Congress would force U.S. industry to cap or roll back its carbon-dioxide emissions unilaterally via the imposition of a "carbon tax."

Even the most draconian restrictions would do little to halt an inevitable increase in greenhouse gases, most of which is occurring outside of the United States. Professor Singer believes that at best we might delay the doubling of these gases by five years--from 2040 to 2045--but at the cost of a trillion dollars in lost output.

There are far less costly ways of dealing with this problem. U.S. forests, for example, already consume more carbon dioxide each year than U.S. industry emits. Only a growing forest consumes this gas, however, so opening up more federal lands for private logging and reforestation would cleanse the atmosphere even more. Creating similar property rights in Brazil and other Third World countries could end the indiscriminate slashing and burning of Third World forests which some scientists believe is the leading source of greenhouse gases.

Our understanding of the link--if any--between economic activity and global warming will be substantially improved in a few years. In the interim there are sensible, free-market responses, which make sense even if no link is found.