James E. Hansen, one of the leading scientists researching global warming, would prefer that the COP15 climate change talks in Copenhagen collapse than result in a fatally flawed deal. "If it is going to be the Kyoto-type thing then [people] will spend years trying to determine exactly what that means," he said. Hansen argues that cutting greenhouse gas emission is not compatible with crafting political compromises. "This is analogous to the issue of slavery faced by Abraham Lincoln or the issue of Nazism faced by Winston Churchill," he said. "On those kind of issues you cannot compromise. You can't say let's reduce slavery, let's find a compromise and reduce it 50% or reduce it 40%." Hansen is also critical of carbon trading. "This is analogous to the indulgences that the Catholic church sold in the middle ages. The bishops collected lots of money and the sinners got redemption. Both parties liked that arrangement despite its absurdity. That is exactly what's happening," he said.