With the COP15 conference fast approaching, the world's political leaders are gearing up to hash out a global agreement that will save us from ever increasing greenhouse gas emissions and the unstoppable climate change that will follow.
New research published this week in Geophysical Research Letters, however, may complicate their plans. The new research, conducted by a professor of Earth Science at the University of Bristol, shows that the balance between the airborne and the absorbed fraction of CO2 has stayed approximately constant since 1850, despite emissions of CO2 having risen from about 2 billion tons a year in 1850 to 35 billion tons a year now.
This conclusion suggests that terrestrial ecosystems and the oceans have a much greater capacity to absorb CO2 than had been previously expected, and the drastic climate scenarios thus far predicted may have to be modified to account for the new data.
The results run contrary to a significant body of recent research which expects that the capacity of terrestrial ecosystems and the oceans to absorb CO2 should start to diminish as CO2 emissions increase, letting greenhouse gas levels skyrocket. Knorr found that in fact the trend in the airborne fraction since 1850 has only been 0.7 ± 1.4% per decade, which is essentially zero.
Perhaps most significant about the new study is that it rests solely on measurements and statistical data, including historical records extracted from Antarctic ice, and does not rely on computations with complex climate models.
The study also found that emissions from deforestation might have been overestimated by between 18 and 75 per cent. This would agree with results published last week in Nature Geoscience by a team from the University Amsterdam. They re-visited deforestation data and concluded that emissions have been overestimated by at least a factor of two.
Despite the controversial findings, Knorr urged caution as scientists try to understand how earth's climate behaves. "Like all studies of this kind, there are uncertainties in the data, so rather than relying on Nature to provide a free service, soaking up our waste carbon, we need to ascertain why the proportion being absorbed has not changed."
Citation: Knorr, W. (2009), 'Is the airborne fraction of anthropogenic CO2 emissions increasing?', Geophys. Res. Lett. Online, doi:10.1029/2009GL040613.
