"We are increasing CO2 production rates, but we are not increasing the rate of CO2 accumulation."
Oh?
Earlier this month, the World Meteorological Organization reported the level of carbon dioxide in the atmosphere reached 379.1 parts per million in 2005, more than 35 percent higher than in the late 18th century
Message 23050378
"CO2 levels will drop rapidly."
CO2 lasts in the atmosphere for about 100 years. Rapid only in geologic terms.
"We have held off the return of the ice age because of huge efforts over a century,"
You could maybe make the case that the atmosphere mellowed at the beginning of the Antropocene Era, which Ruddiman places back 8K years. (Crutzen only puts it back to 1800 AD.) Ruddiman thinks we wrested control of the methane cycle when agriculture began in Asia, New Guinea, and in SE Australia,where eel massive weirs were constructed. You might argue that. Except for the ice core from Dome C at Vostok. Regardless, the rate of change we are causing now far exceeds anything in the past. Old figures, but in '97, we burned, in one year, the fossilized remains of 422 years of photosynthesis; 400 years of sequestered CO2 in one year. This won't stop until we either use all the fossil fuel,or until we go alternate. Then, if we are lucky, Nature's own positive feedbacks won't come into play. (But it looks like maybe it is already warm enuf for that in Siberia and Alaska.)
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Based on current trends, carbon dioxide concentrations are likely to increase to 500PPM this century. The last time the planet experienced levels as high as 500PPM was about 20 or 40 million years ago, when sea levels were 100 metres higher than today.
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