Global warming is the policy issue that refutes Sen. Daniel Patrick Moynihan's axiom that "everyone is entitled to their own opinions, but everyone is not entitled to their own facts." When it comes to global warming, it seems that everyone is entitled--or rather, everyone feels entitled--to his own facts. Many of these conflicting facts are on display at the United Nations climate summit, which got under way this week in Buenos Aires.
Most predictions of global warming are based on "general circulation models." Such models divide the earth's surface and atmosphere into a grid of interconnected cells, and then estimate the rate at which energy and chemicals disperse through the environment. Extrapolate the results, and theoretically you can predict weather and climate over the world as a whole.
The devil is in the details. No one yet fully understands all the physics and chemistry these climate models require. For instance, at what rate do oceans and forests absorb carbon dioxide? On balance, do pollutants trap more heat in the atmosphere or reflect more solar energy into space? Even the best models currently available require some judgment calls.
Moreover, the more precise the model, the more computer capacity one needs to run it. Climate modeling is probably the single most demanding test of computer power. This is why a review article last year in Science, the journal of the National Association for the Advancement of Science, suggested that it may be a decade before computer climate models can link global warming to human activities.
If reliable results are not due for 10 years, what are we doing making global warming policy now? Serious climate scientists understand the limitations--which explains why most avoid making blanket predictions about global warming. The problem occurs when politicians and pundits go into Lewis Carroll mode ("Sentence first--trial afterwards!") and use the results of climate modeling as scientific justification for their preset agenda.
Just this summer, for example, President Clinton suggested man-made global warming was responsible for the drought and forest fires in Florida. Few climate specialists would agree. Probably none would attribute a specific weather event to global warming.
If any of this sounds familiar, it should, because it is a replay of the 1980s "nuclear winter" scare. Back then, politically motivated scientists and dovish policy wonks claimed climate models proved that even a few nuclear explosions would plunge the world into the cold and the dark. They rarely mentioned the limitations of the models, and the media rarely bothered checking. Misused, climate models provide the perfect political argument--an untestable proposition about a hypothetical event, cloaked in a veneer of science.
Using climate models to plan environmental policy today is as risky as, say, extrapolating econometric models to plan global trade. Such policies might prove worse than having no policy at all--and especially when the evidence is being spun to score political points.
All of this is worth keeping in mind as representatives from 166 nations meet this month in Buenos Aires at the Fourth Conference of Parties to implement the Kyoto Protocol on climate change. Current proposals would allot each nation a "quota" of greenhouse-gas emissions, the objective of which is to limit world energy consumption and supposedly culpable economic activities.
Yet it's not even clear that such restrictions would have any effect on global warming. The fact is, climate models only consider the amount of carbon dioxide, methane, and other greenhouse gases present in the atmosphere, not how they arrived there.
Observatories have collected data on atmospheric greenhouse gases for about 40 years. Most data suggest greenhouse-gas levels are rising, but they do not prove human activities are responsible. If you do not know the source of a greenhouse gas, you cannot control it. If you simply guess, which is essentially what we are doing now, the result could be both costly and futile.
The odd thing is that, while we wait for climate researchers to improve their models, we may be overlooking a more straightforward, and possibly more important, test. There are good data available measuring industrial output and global energy consumption since the early 19th century. If there is a link between energy consumption, industry and global temperatures, we should be able to see it.
Some colleagues and I recently ran a few tests using the data to see what patterns might appear. The results: Even allowing for lagging and cumulative effects, it is hard--really hard--to find any correlation between global temperature changes and fluctuations in energy consumption and industrial activity. The well-known relationships between solar cycles and temperature are easy to pick out, but once you control for them, any effect of energy consumption and industry disappears in the background noise.
This is important because restrictions on energy consumption and industry such as those being considered in Buenos Aires would, in effect, replicate the reductions that have occurred in economic downturns. Yet history suggests such reductions would have no effect on global temperatures.
These are preliminary results, and one ought not repeat the error of the climate mavens by overstating their significance. But here is a simple challenge: Before we cut energy consumption or limit industry to control global warming in the future, someone should prove that historic fluctuations have affected global temperatures in the past.
Bruce D. Berkowitz is a writer and consultant based in Alexandria, Va.
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