POSTED JULY 11, 2002
1. Roast, or idle boast?
every heat wave
You hear the same question. Is this global warming? This year, with the massive western wildfires, not to mention the drought afflicting 40 percent of the United States, the question is particularly urgent.
Are the ominous predictions about Earth's climate from 10 to 20 years ago finally coming true? Are we entering a "greenhouse century" of rising seas, shriveled crops, animal extinctions and intense heat waves?
Or is the present warming just another blip on the murky, ever-changing pattern we call climate?
Don't know enough?
Today, the imagined response differs only in intensity. "The past decade has matched our predictions for global warming, but we can never know for sure. Climate is a terribly complex thing, and it would be smartest to assume that warming is happening. We need to reduce greenhouse gas emissions."
So here's the critical question: If climatologists can't give a definitive answer, is it wisest to watch and wait, or to act on what we do know?
The simple science
The debate concerns the extra warming caused by human actions (including the release of greenhouse gases, primarily carbon dioxide, and big changes on Earth's surface).
Because most economic activities cause the release of greenhouse gases, reducing emissions would be expensive. Some evoke this argument in the country's rejection of the Kyoto Protocol, a treaty designed to limit emissions of greenhouse gases. The United States, they say, simply cannot afford to limit its economy in this fashion.
Status quo sauté
Since the first IPCC report in 1991, planetary conditions have given little support to those who doubt global warming. According to Kevin Trenberth, head of the Climate Data Analysis Section at the National Center for Atmospheric Research, the 1990s were the hottest decade in at least 1,000 years.
This spring, amid rising concern from citizens around the world, the Bush Administration renounced Kyoto -- even as the Environmental Protection Agency admitted that much of the ongoing global toast-up can indeed be blamed on human activities, especially burning fossil fuels.
President Bush blamed "the bureaucracy" for his Administration's report.
But consider the following:
Being simple-minded creatures, we Why Filers figured that since the global warming debate heated up more than a dozen years ago, enough time would have passed to check the accuracy of predictions about temperature and sea level.
Warming to the task, we did the obvious thing
Certainly, we found no support for Patrick Michaels, a climatologist and prominent skeptic of global warming. He and others have highlighted supposed errors and inconsistencies in climate data. How, for example, can you be certain about the historic temperatures that were often recorded on urban thermometers? Cities, after all, are warmed by energy released from vehicles, industry and buildings, and this "urban heat island" effect exaggerates temperatures.
Thus any warming recorded in cities says nothing about the globe as a whole. Not so, says Stephen Schneider, a professor of geosciences at Stanford University and an early voice in the warming debate. "If you eliminate large cities or correct for them, it does not change the answer more than 10 percent. The urban heat island has been completely and thoroughly put to bed, it's been analyzed and reanalyzed."
In 1992, Michaels wrote that the gloomy predictions of global havoc are "wrong. The most internally consistent case that can be generated from billions and billions of bits of climatic data simply do not support that vision... The likelihood that we are creating a better world far outweighs the probability of climate apocalypse" (see "Sound and Fury" in the bibliography).
That does not reflect the consensus of climatologists, as reflected in the IPCC.
However, we did find support for a frustrating truth that's plagued the warming debate since the start: We may not have a definitive, scientific answer about the human impact on climate until far too late.
First things first. What have thermometers told us about climate?
©2002, University of Wisconsin, Board of Regents.