From the Union of Concerned Scientists:

http://www.ucsusa.org/news/press_release/investigation-reveals-0007.html

Here's an excerpt:

"UCS distributed surveys to 1,600 climate scientists, asking for information about the state of federal climate research. The scientists who responded reported experiencing at least 435 occurrences of political interference in their work over the past five years. Nearly half of all respondents (46 percent) perceived or personally experienced pressure to eliminate the words "climate change," "global warming," or other similar terms from a variety of communications. Forty-three percent of respondents reported they had perceived or personally experienced changes or edits during review of their work that changed the meaning of their scientific findings. And nearly half (46 percent) perceived or personally experienced new or unusual administrative requirements that impair climate-related work."