Carbon keeps rising while Earth absorbs less, study finds

New research from an international team of scientists has found that the Earth’s natural carbon sinks could be becoming less efficient at absorbing carbon dioxide from the atmosphere.

The study is published this week in the journal Nature Geoscience.

The research team, working under the umbrella of the Global Carbon Project, found that the average proportion of carbon dioxide emissions remaining in the atmosphere each year has likely risen from 40 per cent to 45 per cent over the past 50 years. The shift indicates that natural carbon sinks are responding to climate change and variability.

The scientists also report that global carbon dioxide emissions from fossil fuels increased by 29 per cent between 2000 and 2008, and even rose by 2 per cent in 2008 despite the global economic downturn.

“The only way to control climate change is through a drastic reduction in global CO2 emissions,” said Corinne Le Quéré of the University of East Anglia (UEA) and the British Antarctic Survey and the study’s lead author. “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 CO2 concentrations 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.”

Other findings from the study include:

• CO2 emissions from the burning of fossil fuels rose by 41 per cent between 2008 and 1990, the reference year of the Kyoto Protocol.
• CO2 emissions from the burning of fossil fuels have increased at an average annual rate of 3.4 per cent between 2000 and 2008, compared with 1 per cent per year in the 1990s.
• Emissions from land use change have remained almost constant since 2000, but now account for a significantly smaller proportion of total anthropogenic CO2 emissions (20 per cent in 2000 to 12 per cent in 2008).
• Emissions from coal are now the dominant fossil fuel emission source, surpassing 40 years of oil emission prevalence.
• Emissions from emerging economies such as China and India have more than doubled since 1990 and developing countries now emit more greenhouse gases than developed countries.
• A quarter of the growth in CO2 emissions in developing countries can be accounted for by an increase in international trade of goods and services.

The research team has called for more work to be done to improve our understanding of the land and ocean CO2 sinks, so that global action to control climate change can be independently monitored.