This just a short "place holder" statement.
The title is taken from the Al Gore documentary on climate change, but you don't need to agree with everything that was said in that to support this camp. This is about just that one inconvenient truth: that carbon dioxide emissions due directly to human activities will and in fact are already affecting the global climate to an extent that is at least very serious, and potentially disastrous.
The evidence? The reports of the Intergovernmental Panel on Climate Change (IPCC) are extremely important, but in practice, the Real Climate website (http://www.realclimate.org) is a great place to start, because it's interactive and up-to-date, it's run by actual climate scientists, and it directly addresses many of the myths about climate change that circulate within the skeptic community.