The Climate Blogosphere is all a flutter over a recent study:
The gist that has people excited or concerned is that the portion of the CO2 we emit that stays in the atmosphere has remained more or less constant. It has been hypothesized by some that as warming increases, the earth will lose it’s ability to absorb our CO2 gradually. Since our emissions are increasing, if the sinks were constant, the ratio would be increasing gradually. If sinks were absorbing less CO2 then there would be a rapid increase. But if the ratio has stated the same, that means that the amount of CO2 that is absorbed by the Oceans and biosphere etc. is increasing. In other words, we emit more, and the Earth’s capacity to absorb CO2 increases proportionally. This is exactly the opposite of the “CO2 feedback” hypothesis, that a warmer world will be less able to absorb CO2. Thus more of our emissions will stay in the atmosphere, which means more warming, rinse lather repeat.
But we already knew this. Search google for “missing sink” to find plenty of articles that explain that there is a bunch of carbon dioxide that is emitted into the atmosphere that carbon cycle modelers have no clue what happens to. There are a lot of hypotheses, but the issue at present is still unresolved. What’s more, it has long been know that our emissions are more than enough to account for the increase in CO2 concentrations, so that the “missing” amount of CO2 is increasingly large and difficult to account for.
One possible explanation is that the biosphere is absorbing more CO2 through photosynthesis. I don’t know if anyone is testing this but it would make sense and fits with studies indicating increases in primary productivity.
Yet in spite of this not being news, you haven’t heard it, most likely, until now. Well that’s probably because it is surprisingly good news. Logically as warmer oceans lose their ability to sequester CO2 and as higher temperatures presumably result in release of “trapped” carbon from permafrost (in the case of methane this is VASTLY contradicted by observational evidence). If that were the case then the airborne fraction would have to be increasing. Since it is not, it appears that the carbon cycle feedback hypotheses are not supported at present by the evidence.