If human-induced climate change continues unchecked, 10 percent of the U.S. economy could evaporate by 2100, a 1,656-page federal report the White House slipped out on Black Friday (Nov. 23) warned — but a nearby world has an even hotter climate problem than ours, and scientists say we could learn some valuable lessons from it. That world is Venus, Earth's "evil twin," which was once nice enough — until something went wrong and the atmosphere began trapping a little too much heat. Scientists aren't positive precisely how events played out, but the runaway greenhouse effect that resulted is beyond debate:...