"Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities,1 and most of the leading scientific organizations worldwide have issued public statements endorsing this position." http://climate.nasa.gov/scientific-consensus
NASA: Climate Change - How do we know?
Great overview of the evidence from a science-based source.
A short review of how the jetstream and Rossby waves work, and some emerging indications that the dynamics may be changing in a warming world.