350 ppm

I was aware of 350.org. I was not aware until today that we passed 350 ppm in 1988.

Thanks to Geoff Styles, who makes a good “the great is the enemy of the good” point:

As it is, President Obama is taking a considerable risk in offering emission cuts that have not been approved by Congress, which might not be inclined to stick out its neck quite so far going into a tough mid-term election that will hinge on the economy and employment. While China's offer represents a serious first step, a similar focus on "carbon intensity" by the previous US administration was met with derision by environmentalists. The problem is that the level of emissions this would yield if China's economy continues to grow at 8% per year or more is incompatible with scenarios for limiting peak CO2 concentrations in the atmosphere to 450 parts per million and eventually restoring them to pre-industrial levels. If we can't avoid blowing past the 450 ppm limit that was the basis of the Bali framework, then growing efforts to shift the official goalpost back to 350 ppm--a level we passed in 1988--look like King Canute ordering the tide not to rise. Expect a great deal of attention to be focused on these numbers in the next couple of weeks.