You're probably going to hear a lot today about the Intergovernmental Panel on Climate Change's most recent report and predictions of the impacts of global warming. This is the IPCC's first of four reports on the subject, and it documents beyond any reasonable doubt that global warming is happening and that it is mostly caused by humans.
Andrew Weaver, a Canadian climate scientist and co-author of the study, took the "smoking gun" analogy one step further:
"This isn't a smoking gun; climate is a battalion of intergalactic smoking missiles."
Check out Celsias's excellent report on the report.