Deep Pockets : Carbon Sinks News

Possibly some good news from the world of Carbon Sink science : the Earth may be soaking up progressively more Carbon Dioxide as time goes by instead of refusing to do so :-

“Is the airborne fraction of anthropogenic CO2 emissions increasing? Wolfgang Knorr : Department of Earth Sciences, University of Bristol, Bristol, UK : Several recent studies have highlighted the possibility that the oceans and terrestrial ecosystems have started loosing part of their ability to sequester a large proportion of the anthropogenic CO2 emissions. This is an important claim, because so far only about 40% of those emissions have stayed in the atmosphere, which has prevented additional climate change. This study re-examines the available atmospheric CO2 and emissions data including their uncertainties. It is shown that with those uncertainties, the trend in the airborne fraction since 1850 has been 0.7 ± 1.4% per decade, i.e. close to and not significantly different from zero. The analysis further shows that the statistical model of a constant airborne fraction agrees best with the available data if emissions from land use change are scaled down to 82% or less of their original estimates. Despite the predictions of coupled climate-carbon cycle models, no trend in the airborne fraction can be found. Received 18 August 2009; accepted 23 September 2009; published 7 November 2009. Citation: Knorr, W. (2009), Is the airborne fraction of anthropogenic CO2 emissions increasing?, Geophys. Res. Lett., 36, L21710, doi:10.1029/2009GL040613.”

“Controversial new climate change results : New data show that the balance between the airborne and the absorbed fraction of carbon dioxide has stayed approximately constant since 1850, despite emissions of carbon dioxide having risen from about 2 billion tons a year in 1850 to 35 billion tons a year now. This suggests that terrestrial ecosystems and the oceans have a much greater capacity to absorb CO2 than had been previously expected. 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. Dr Wolfgang Knorr at the University of Bristol 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…”

“…So is this good news for climate negotiations in Copenhagen? “Not necessarily”, says Knorr. “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”. Another result of the study is 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 led by Guido van der Werf from VU University Amsterdam. They re-visited deforestation data and concluded that emissions have been overestimated by at least a factor of two.”

“Commentary : Nature Geoscience 2, 737 – 738 (2009) : doi:10.1038/ngeo671 : CO2 emissions from forest loss : G. R. van der Werf, D. C. Morton, R. S. DeFries, J. G. J. Olivier, P. S. Kasibhatla, R. B. Jackson, G. J. Collatz & J. T. Randerson : Correspondence to: G. R. van der Werf e-mail: : Abstract : Deforestation is the second largest anthropogenic source of carbon dioxide to the atmosphere, after fossil fuel combustion. Following a budget reanalysis, the contribution from deforestation is revised downwards, but tropical peatlands emerge as a notable carbon dioxide source.”

And as the Antarctic ice cap retreats, there’s more opportunity for marine plants to grow and soak up CO2 :-

“Ice retreat opens new shores for carbon storage : 9 November 2009, by Sara Coelho : Ice melting in Antarctica has opened a new area of sea as big as Wales, where tiny marine plants called phytoplankton can bloom and absorb extra carbon from the atmosphere. But before we open the champagne, this positive effect does not offset the damage done by carbon emissions. Global warming is causing unprecedented melting in Antarctica’s glaciers and the break-up of many ice shelves along the Antarctic Peninsula. But new opportunities for life arise as the glaciers retreat and shore waters become exposed to light and circulation of nutrients. Without ice cover, carbon-absorbing phytoplankton moves in and starts taking up extra amounts of carbon dioxide from the atmosphere, becoming what scientists call a ‘carbon sink’. ‘This is really massive – it’s like having a new forest the size of Wales,’ says Professor Lloyd Peck, a near-shore marine biologist from the British Antarctic Survey. Peck estimates that this new natural sink is taking up 3.5 million tonnes of carbon dissolved in the ocean. This is the amount of carbon absorbed by the equivalent of between 6,000 and 17,000 hectares of tropical rainforest. However, ‘this is a very small amount compared to the global emissions of greenhouse gases in the atmosphere,’ he says. It is, nevertheless, an important discovery: ‘It shows nature’s ability to thrive in the face of adversity,’ says Peck, who led the study published this week in Global Change Biology…”

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