Editor's note: This week the American Enterprise Institute, a Washington-based think tank where TCS host James K. Glassman is a fellow, is holding a symposium on climate change issues called "Return to Rio: Reexamining Climate Change Science, Economics and Policy." AEI asked scientists and other interested parties from around the country to participate. In the interest of balance, AEI asked several proponents of the hypothesis of an anthropogenic greenhouse effect to participate but were turned down consistently. One of those who enthusiastically accepted, however, was Martin Hoffert, a professor of physics at New York University. Professor Hoffert originally agreed to...