August 04, 2004,
Two recent findings, one right next to Washington D.C., the other as far away as is possible to imagine, demonstrate the limits of what we can learn from scientific models. When researchers put together theories to predict what should happen, that's a model. When the model conflicts with reality, the model is flawed. Yet there are some scientists who don't accept that, which should give us pause to think about their claims.
We saw it in late July when the Washington Post reported that water samples from the major rivers pouring into the Chesapeake Bay showed no declines in the presence of two major pollutants since the mid-1980s. Yet the computer model that the Chesapeake Bay Program used to report progress in environmental cleanup estimated a 40-percent reduction in the pollutants. That model had been praised as the "Cadillac of watershed models" and "well-constructed and useful for prediction." The program has accepted the criticism and adjusted its model.
We also saw it in the recent discovery by astronomers of very old galaxies far out in space, in places where the current state-of-the-art models predict there should only be very young galaxies. The scientists have taken the news in their stride, admitting that much of what they thought happened in the early universe was wrong.
We see this sort of thing all the time in science. British scientists whose models at one time were predicting hundreds of thousands of human deaths as a result of "mad cow disease" now only predict another 40 or so. Even Stephen Hawking admitted this week that he was wrong on a theory about black holes he first formulated in the 1970s.
Scientists change their minds when data contradicts their models except in one area, the relatively new scientific discipline known as climatology.
If the climate models that predict massive rises in temperature over the next century are correct, the atmosphere should warm before the surface. But atmospheric data from both satellites and weather balloons show only a trifling rise in temperature over the past couple of decades, while the surface temperature has been rising steadily. In 2000, a National Research Council study confirmed the data's discrepancy with the model.
The proper scientific response would be to reexamine the models and adjust them to fit reality. But that hasn't happened in climatology. Instead, there have been repeated attempts to manipulate the satellite data fit the models. Recently, a study published in the journal Nature tries to hammer the square peg of the satellite data into the round hole of the theory, using a method that satellite temperature experts John Christy and Roy Spencer of the University of Alabama at Huntsville had considered and rejected as incorrect in 1991. And when distinguished economists David Henderson and Ian Castles pointed out that the economic assumptions used by the Intergovernmental Panel on Climate Change (IPCC) used inappropriate methods of estimating future economic growth, leading to overestimates of the amount by which the global temperature would rise, they were met with abuse from the IPCC rather than the detailed reexamination their criticisms required.
The world has been down this road before. Until Copernicus proved that the Earth revolved around the sun, astronomers tortured measurements of the stars' and planets' positions in the heavens to fit the prevailing religious theory that the Earth was the center of the universe. Modern astronomers and the Chesapeake Bay Program know that even the best models can't replace reality. Perhaps global warming theory is closer to religion than to science.
Iain Murray is a senior fellow at the Competitive Enterprise Institute, where he specializes in the debate over global warming and the use and abuse of science in the political process.