Model Madness

Bay Pollution Progress Overstated At news conferences, on its Web site and in its regular publications, the government agency leading the cleanup of the Chesapeake Bay has documented more than a decade of steady progress. The Chesapeake Bay Program has reported that the flow of major pollutants from rivers into North America's largest estuary has declined nearly 40 percent since 1985, bolstering the claims of politicians in Virginia, Maryland, Pennsylvania and the District that they were "saving the bay" and helping the states fend off criticism and lawsuits from environmentalists. Those reports, however, significantly overstated the environmental achievements. The estimates of pollution reduction were based on a computer model -- not water samples -- that program officials now say was distorted by overly generous assumptions.

The modelers claim that this is just how science works, and models always need improvement. That's true. It's been sobering for me to listen to some of my professors here, who are on the cutting edge of land change modeling, explain how poorly their models do. But given that, and given the fact that you can (and have) directly test the factor in question, who in their right mind would rely on a model? You use models for things you can't directly measure (such as the future).