Washington Post: Economist Robert Pindyck of the Massachusetts Institute of Technology recently examined the computer models that estimate the effects and costs of climate change -- and he didn't like what he found. The models reflect two gaping uncertainties, he says. First, we don't know how much increased atmospheric carbon dioxide (CO2) will raise global temperatures. "There are feedback loops' -- interactions between greenhouse gases and weather -- "that aren't easy to measure.' The models make assumptions....