CO2 emissions outstrip carbon sinks

The rise in atmospheric carbon-dioxide emissions continues to outstrip the ability of the world’s natural ‘sinks’ to absorb carbon, according to an international team of researchers.

The team, under the umbrella of the Global Carbon Project, found that over the last 50 years the average fraction of global CO₂ emissions that remained in the atmosphere each year was around 43 per cent. The rest was absorbed by the Earth’s carbon sinks on land and in the oceans.

During this time this fraction has likely increased from 40 to 45 per cent, suggesting a decrease in the efficiency of the natural sinks. The team believes that the sinks are responding to climate change and variability.

The scientists reported a 29 per cent increase in global CO₂ emissions from fossil fuel between 2000 and 2008 (the latest year for which figures are available) and said that, in spite of the global economic downturn, emissions increased by two per cent during 2008.

The use of coal as a fuel has now surpassed oil and developing countries now emit more greenhouse gases than developed countries - with a quarter of their growth in emissions accounted for by increased trade with the West.

Researcher Corinne Le Quéré of the University of East Anglia and the British Antarctic Survey said: ‘The only way to control climate change is through a drastic reduction in global CO₂emissions. The Earth’s carbon sinks are complex and there are some gaps in our understanding, particularly in our ability to link human-induced CO₂ emissions to atmospheric CO₂concentrations on a year-to-year basis. But, if we can reduce the uncertainty about the carbon sinks, our data could be used to verify the effectiveness of climate-mitigations policies.’

The research team also found that the financial crisis had a small but discernable impact on emissions growth in 2008, with a two per cent increase compared with an average three to six per cent over the previous seven years. On the basis of projected changes in GDP, emissions for 2009 are expected to fall to their 2007 levels before increasing again in 2010.

The researchers are calling for more work to be done to improve understanding of the land and ocean CO₂ sinks so that global action to control climate change can be independently monitored.