Oh, and in case anyone wants to try the "the globe actually cooled from 1940 to 1970," let me just nip that in the bud. When industrial countries were pumping out sulfur dioxide in huge amounts, the steady rise in temps did stop for a while, because sulfur compounds in the air create a cooling haze. That's why major volcanic events are often followed by a cooler than normal year, as sulfur compounds shot into the stratosphere have a temporary cooling effect until they are precipitated out of the air. Around 1970, several environmental agencies in major industrial countries (in response to the damages from acid rain, caused by S02 in the air), banned the high-sulfur fuels and required stack controls, which greatly reduced SO2 output. As a result, S02 rapidly dropped, and the Keeling curve quickly reasserted itself and temps began rising again. And no, bringing back acid rain would not be a good solution to GW.