The Chicken Littles who had the last word on the International Panel on Climate Change tell us that the sky is falling again.
The panel of scientists comprising the IPCC recently reported on the state of, and potential outlook for, earth's climate. Doubts, disagreements and contradictory data can be found in the body of the report. But the group who wrote the executive summary, the only part that will be widely read, pretty flatly assert that humans are causing global warming.
Based on the executive summary and the policy options presented in it, environmentalists say the world's governments must take drastic action now to halt the cataclysmic consequences of such a change. Analysts at the World Watch Institute, for example, call for an overhaul of our energy and transportation systems, ending the fossil fuel economy. Such policies would cost our nation billions of dollars.
Before we head for cover, let's consider whether the sky really is falling, or whether some Chicken Littles in the ranks of scientists have been led down the garden path by a figurative acorn, in the form of computer climate model data, falling on their heads.
Proponents of the theory of global warming, or, as is now fashionable, "global climate change," depend on two bits of evidence and computer models. First, ground-level measurements of global mean temperature indicate that earth has warmed between 0.3 and 0.6 degrees Celsius in the last century. Second, atmospheric carbon dioxide (CO2), a primary greenhouse gas (those gases without which most animal and plant life would not exist), has increased by approximately 25 percent in the last century and a half.
When you put these facts in the computer models, global climate change theory says that the earth's current warming is due to the increase of CO2 in the atmosphere, caused primarily by the use of fossil fuel. According to the models, absent a severe and immediate reduction in the level of CO2 put into the atmosphere, the earth will warm further, causing all manner of calamities from melting polar ice caps which would raise ocean levels, flooding small islands and coastal regions, to increased hurricane activity and severe droughts, which would cause massive crop failure.
The IPCC report's executive summary predicts that if no further action is taken to curb greenhouse gas emissions, we can expect an increase in temperature somewhere between 0.8 and 3.5 degrees Celsius over the next 100 years. Interestingly, this figure is well below the amount of warming forecast just four years ago. In fact, with every new report, the range of warming falls. At this pace, in a few years scientific doomsayers will be talking about the next ice age again. (We haven't forgotten that that was this same group's doom and gloom scenario in the 1970s.)
Even if the current figure is correct, the increase is well within the natural range of known temperature variation over the last 15,000 years. Most of the earth's plant life evolved in a much warmer, CO2-filled atmosphere. In fact, the predicted warming would affect primarily night-time temperatures, lessening the number of frosty nights and extending the growing season.
However, there is little evidence that increased CO2 has had more than a small part to play in this century's temperature increase. Most of the warming occurred before the 1940s, before the widespread use of automobiles. In fact, from 1938 to the present, we have actually experienced a cooling trend. Indeed, satellite data, the most reliable climate evidence that we have, show no evidence of warming.
So why do scientists agree that we must take drastic action now? Well, they don't. Some scientists are proclaiming impending disaster, but others of at least equal repute say the evidence of global warming is questionable at best. So this is not a question of proven science versus a bunch of know-nothings.
And why do they agree, as the executive summary says, that we should take drastic action now to curb fossil fuel use, limit economic growth in established countries, and condemn less-developed countries to continue in their less-developed circumstances, and increase unemployment and misery all around? They don't agree with that either. Even some of climate change theory's foremost scientific advocates acknowledge that there is nothing we can do now to prevent global climate change that we won't be able to do 10 years from now.
A far better course of action is to keep studying, keep learning, and keep improving our data until we understand what, if anything, is really happening. Then we can take action that will allow economic growth and a higher standard of living and keep our planet livable. Both must be accomplished together; we must not sacrifice one to achieve the other.