For some years, climate scientists avoided public debate on global warming, partly on the ground that skeptics didn't deserve a hearing. Now, so many Republican non-believers have been elected to Congress that the US may become almost unique among nations in dismissing the problem. As fossil-fuel industries celebrate, scientists are now speaking out, with another world conference on climate change later this month in Cancun. Will the US be able to play any role? What about the Obama Administration's fight against greenhouse pollution at home?