[W]e are reaching the point where we can see that we are starting to make massive, probably irreversible, changes to our climate. The glaciers are in full retreat almost everywhere, the Arctic is melting (with total melting of the summer sea ice possible, though not certain, as early as 2020), the permafrost is melting, and releasing large amounts of methane, which is a very powerful global warming gas, while in the last thirty years, droughts have doubled due to warming, hurricanes are much more intense all over the globe, and are showing up in places they never did before in recorded history. Scientists have been projecting changes in ocean circulation, and lo-and-behold, they are starting to show up, including changes to the North Atlantic Circulation, although major change here was previously thought unlikely this century. There is some possibility of changes in deepwater circulation destabilizing methane hydrates in the ocean, particularly in South East Asian deeps. Oh, and the Greenland ice sheet is now melting much faster than climatologists expected, and the West Antarctic ice sheet is starting to collapse, though again, this was previously thought unlikely. Also paleoclimatological studies have made it clear that in the past the climate abruptly flipped between modes, sometimes with dramatic change in as little as three years. And we are making rapid changes in carbon dioxide, known to be critically important in regulating the temperature of this sensitive climatic system for a century now.

As he says, "maybe there's some scientific doubt still on any individual piece of the picture, but the gestalt is starting to look extremely alarming." Yes