Environmental activists are increasing the heat on policy makers worldwide to do something about global warming before it is too late. They charge that human activity is already warming the planet—yet the climate is not cooperating. Thus far, 1996 has been a cool year. Much of the East coast experienced record snowfalls this winter, and May was the sixth consecutive month of temperatures below seasonal norms, according to global satellite measurements.
Only several months ago the British Meteorological Office reported that 1995 was the hottest year on record, edging out 1990 by a bare 0.07 degrees F. Environmental activists proclaimed the announcement as further evidence that human-induced global warming had arrived.
Yet all was not right with the data. The designation of 1995 as the "warmest year on record" was based on incomplete measurements. As readings for only the first 11 months of the year were available, the British scientists estimated December temperatures. The excluded data revealed a record, end-of-year nose dive throughout the Northern Hemisphere. The complete data set for 1995 gathered from satellite readings revealed a thoroughly average year —only the eighth warmest since the satellites began taking climate measurements.
Most global warming predictions are based on general circulation models (GCMs), immensely complex computer simulations. Environmentalists tend to put a lot of faith in the predictive capacity of the computers. Others suggest that the model projections are hooey. Dr. Richard Lindzen at the Massachusetts Institute of Technology compares model output to predictions from a ouija board, and with some cause. According to the models, the earth should be significantly warmer than it is.
Climate computer programmers have had a difficult time including all of the myriad variables that affect the climate, such as clouds and precipitation. One problem of existing models, for instance, is that they are unable to replicate weather fronts. Recent scientific evidence suggests that models do not sufficiently account for the impact of the sun either. Several recent studies have suggested a possible correlation between temperature trends and solar cycles. As Science magazine reported, "the sun could have been responsible for as much as half of the warming of the past century. If so, the role of greenhouse gases... would dwindle—as would estimates of how much they will warm climate in the future as they continue to build up."
As the computer models have become more accurate, their predictions have become less severe. For instance, the latest models have sought to incorporate the potential cooling effect of industrial emissions. The result is the lowest projected temperature change generated by a computer model to date. The model upon which the most recent UN Intergovernmental Panel on Climate Change report is based predicts a warming of 0.8 to 3.5 degrees centigrade by the year 2100. This is significantly less warming than has been predicted in the past. Indeed, the lower-bound warming estimate is approximately half that predicted just four years ago.
It is certainly possible that human activity will contribute to a warming of the planet. Yet this fact, of itself, is no cause for alarm. How warming would occur is immensely important. Scorching summers, produced by an increase in daytime highs, would have far different effects on human and other life than a wintertime warming that occurs mostly at night. Where the warming is concentrated is also a real concern, as is what effect warming has upon precipitation. Whether environmentalists choose to accept it or not, there are many indications that a warmer world would be far more benign than previously imagined. Some research even suggests that a moderately warmer climate would be a far better one for humanity.
The real question facing the world's people is not "is warming real?" but "what, if anything, should be done about it?" Future events will always be indeterminate, and given the magnitude of human activity, this means there will be uncertainty about the impacts of civilization. Natural disasters will strike randomly whether modern industrial society warms the earth or not. Even the most sophisticated computers will be forever unable to forecast future events with anything approaching certitude. What then is the proper policy response to uncertainty?
By all estimates, only incredibly severe reductions in global carbon dioxide emissions—on the order of 60 percent or more — will alter the computer forecasts. The resulting economic dislocations would be tremendous, potentially outweighing the negative impacts of even the most apocalyptic warming scenario. Global warming may pose uncertain risks, but the risks of global warming policies is clear.
The arguments for dramatic greenhouse gas reductions are all variants of the precautionary principle, essentially that it is better to be safe than be sorry. If only it were that simple. It is true that economic growth and technological advance pose environmental risks. But stagnation is hardly a safer course. In the words of the late Aaron Wildavsky:
"the results of doing too much can be as disastrous as doing too little."
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