An Astronomer Questions Environmental Consensus on Global Warming

July 03, 1994|By MICHAEL K. BURNS

Sunspots get the blame and credit for a lot of things that happen on Earth. The regular cycles of these short-lived solar magnetic storms have been used to forecast human fertility, the stock market, weather conditions and agricultural production. That doesn't include the numerous earthly, and extraterrestrial, activities linked to sunspots by the supermarket tabloids.

So when astronomer Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics suggests that sunspot cycles may be the mechanism behind global warming, you can see the collective eyebrows rising.

Sunspots signal changes in the sun's brightness or energy level, which in turn may regulate the Earth's temperatures, she explains. Sunspot cycles appear to be mirror images of warming and cooling periods on Earth.

That's a direct threat to the environmental orthodoxy that man's insatiable lust for carbon combustion is the primary cause of the "greenhouse effect" and global warming.

Dr. Baliunas is not only challenging the science of the Greenhouse Gang, but their sacred political credo as preached by high priest Al Gore, who calls global warming "the highest risk environmental problem the world faces today."

That's the urgency behind the White House's wide-ranging program to curb human energy consumption and combat the potential threat of global warming. The assumption is that man is largely responsible for a half-degree (0.5) Celsius increase in average global temperatures over the past century. Industrial and automotive burning of fossil fuels has accelerated the accumulation of carbon dioxide in the atmosphere.

Dr. Baliunas is one of a number of scientists who are questioning the political rush to judgment on global warming. Wait another five years, as more reliable satellite weather data become available for analysis, she urges, before making costly and restrictive policy decisions on energy use.

Scientists generally agree that the average temperature of the Earth, based on actual readings around the globe, has risen by a half-degree between 1890 and 1990. They know that carbon dioxide has been accumulating in the atmosphere over that time and that these gases trap heat, creating a "greenhouse" that prevents heat from radiating out into space, warming the Earth's surface instead. Other human-generated greenhouse gases, of

much smaller proportion but also increasing, include methane (landfills, livestock), nitrous oxide (combustion) and chlorofluorocarbons (refrigeration, aerosol propellants).

The broad debate is over interpretation of that temperature increase, the rate and level of global warming, and the relative role of man-made carbon dioxide as a direct cause.

Using controversial computer models, global-warming Jeremiahs jolted the world by claiming that man's unchecked industrial and automotive use of fossil fuels could raise the Earth's surface temperature by as much as 5 degrees Celsius a century from now. The result would be catastrophic drought, flooding, deforestation and pestilence.

Thus the Earth Summit held in Rio de Janeiro two years ago produced a worldwide pledge to cut back man-caused carbon dioxide gases to 1990 levels. The United States signed and ratified that convention, and the Clinton administration announced a largely voluntary program last year to reduce American outflow of greenhouse gases by about 8 percent. The price tag was estimated at $65 billion.

Nay-sayers point out that the Earth has experienced extensive climate shifts, for reasons that are not well understood. "Ice ages" have popped up after centuries of relative warmth. The most recent hundred-year temperature change may be insignificant, and it may not inexorably lead to higher and higher surface temperatures.

If the mounting combustion of carbon fuels is the main cause, surely it would have caused some uptick in that recent time period.

In fact, a major objection to the global warming theory is that the computer models used by proponents predict that the major part of the half-degree change should have occurred over the past 50 years, when the volume of man-caused carbon dioxide emissions has accelerated.

Actual observations, however, show that nearly 90 percent of that century-long increase occurred before 1940. In addition, Dr. Baliunas maintains, the United States has shown no warming trend over the past half-century, despite being the center of human carbon dioxide production. The Arctic region, which greenhouse computer models predict to experience a large temperature increase, also shows no warming trend.

"If the greenhouse warming were as large as computer climate models say, it would have left a clear mark in the temperature record," says Dr. Baliunas. "The mark isn't there." In fact, a 50 percent increase in carbon dioxide has already occurred since pre-industrial levels, without perceptible harm to the planet, she notes.

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