Last month a coalition of 18 Scientific organizations (and these are big ones...some of the biggest in the world) issued this statement (PDF) to the Senate:

Dear Senator:

As you consider climate change legislation, we, as leaders of scientific organizations, write to state the consensus scientific view.

Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver.  read more »