Two private advocacy groups told a congressional hearing Tuesday that climate scientists at seven government agencies say they have been subjected to political pressure aimed at downplaying the threat of global warming. The groups presented a survey that shows two in five of the 279 climate scientists who responded to a questionnaire complained that some of their scientific papers had been edited in a way that changed their meaning. Nearly half of the 279 said in response to another question that at some point they had been told to delete reference to "global warming" or "climate change" from a report....