Hot Times for the Old Orb

By Frederic Golden

Government studies warn of dramatic changes in climate

The doomsday headlines (SUNBELT MOVING NORTH, WARMING SPELLS DISASTER) were unduly alarmist, and much of the information was well known to scientists. But last week a media brouhaha was triggered by new studies from the Environmental Protection Agency and the National Academy of Sciences. Both groups agreed on a startling prognosis: the earth is warming up from all the carbon dioxide being spilled into the atmosphere by the burning of fossil fuels, and worse, the first effects of the climatic changes could be felt as early as the 1990s.

The EPA predicted temperature increases of nearly 4DEG F by the year 2040; a rise in sea levels of 2 feet by 2025 (thereby inundating some low-lying areas in coastal cities such as Charleston, S.C., and Galveston, Texas); and drastically changing rainfall patterns, especially in the breadbasket areas of the Midwest, where reduced precipitation could jeopardize crops. Nothing, not even a sharp cutback in the use of fossil fuels, the EPA added, could alter this climatic course.

Several days after these findings hit the front page, the academy's congressionally commissioned report strongly echoed the EPA's gloomy long-range forecast. While it was couched in less dramatic terms, the study provided more fresh science, based largely on computer models. It warned that CO2 concentrations could double by late in the 21st century, increasing global temperatures by as much as 7DEG. The rich, irrigated farming areas of California and the Texas Gulf would dry out, and agriculture would shift to the north. Like the EPA findings, the 496-page document called for more research to determine how best to cope with the changing conditions. The situation, it said, requires "caution, not panic."

Some areas might actually profit from the shifts. The Northeast, for example, could get a more benign climate, not unlike Florida's. Canada's growing season might lengthen, and some deserts would begin to bloom. In addition, the extra CO2 might increase the rate of photosynthesis, encouraging more vigorous plant growth. The reports also pointed out that effects could be mitigated by tactics like switching to crops more suitable for the new conditions.

But even EPA Administrator William

Ruckelshaus professed surprise at the strong public reaction. After all, he pointed out, "we can't say any of these things for certain." Scientists noted that researchers have been cautioning for nearly a century that the burning of fossil fuels (coal, oil, natural gas) is steadily increasing the atmosphere's CO2 content. The invisible gas itself is not dangerous. In fact, it is vital to green plants, which combine CO2 with water in the presence of sunlight to produce carbohydrates.

But plainly there can be too much of a good thing. As the amount of atmospheric CO2 increases beyond the capacity of plants or the oceans to reabsorb it, the gas acts as a thermal blanket. It allows the sun's rays to pass through it, like the glass of a greenhouse, but blocks longer infrared, or heat, waves given off by the earth's surface from radiating back into space. Gradually, as CO2 levels rise, the atmosphere gets warmer. It retains more water vapor, adding still another "greenhouse" gas that traps heat. Meanwhile, the temperature of the earth's surface rises, melting snow and ice. The water swells the oceans, because of both the runoff and the water's heat-induced expansion. At the same time, as the polar icecaps shrink, the planet's total reflectivity decreases. Result: the earth bounces less sunlight back into space and heats up even more. Says Robert Schiffer, manager of NASA'S climate-research program: "It's all straightforward physics."

Straightforward perhaps, but hardly the entire picture. For example, scientists still do not know whether the ability of the oceans to soak up CO2 from the atmosphere is even close to the limit. They also are uncertain about the precise role of other atmospheric components, such as dust particles, increased cloud cover and sulfur dioxide, all of which tend to produce a cooling effect. A more remote possibility: a major volcanic eruption could darken skies round the world for several years, as Krakatau did a century ago, or there could be unexpected fluctuations in the sun's radiation, perhaps a factor in past ice ages. As Geophysicist William Nierenberg of the Scripps Institution of Oceanography, the academy panel's chairman, acknowledges, "The issue is full of uncertainties."

Yet for all the unanswered questions, there appears to be little doubt among scientists that a troubling CO2 buildup is leading the earth into a period of major climatic uncertainty. NASA's Brian Toon has been studying the greenhouse effect on hot, cloud-covered Venus (surface temperature: 900DEG F). He concludes, "We're on the ragged edge of convincingly demonstrating that it's happening on earth as well." At the very least, as the studies urge, the inhabitants of the planet must begin looking more seriously into how they might live in a new, hotter world.

-- By Frederic Golden. Reported by Jay Branegan/Washington, with other bureaus

With reporting by Jay Branegan This file is automatically generated by a robot program, so viewer discretion is required.