Thu, Nov 19, 2009 page6

• Carbon dioxide output rose 29% in past decade

  GLOBAL CARBON PROJECT New research indicates forests, oceans and soil are less efficient at absorbing carbon emissions than they were just 50 years ago

  • THE GUARDIAN
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  Scientists said that carbon dioxide emissions have risen by 29 percent in the past decade alone and called for urgent action by leaders at the UN climate talks in Copenhagen to agree drastic emissions cuts in order to avoid dangerous climate change.

  By studying 50 years of data on carbon emissions from human and natural sources, such as volcanoes, a team of international researchers was able to estimate how much carbon dioxide is being absorbed naturally by forests, oceans and soil.

  They concluded, in the journal Nature Geoscience, that those natural sinks are becoming less efficient, absorbing 55 percent of the carbon now, compared with 60 percent half a century ago.

  The drop in the amount absorbed is equivalent to 405 million tonnes of carbon, or 60 times the annual output of the largest coal-fired power station in the UK.

  The carbon dioxide absorbed by a natural carbon sink can be adversely affected by annual variations in weather and rising concentrations of the gas in the atmosphere.

  Corinne Le Quere of the University of East Anglia, England, who led the study with colleagues at the British Antarctic Survey, suggested that rapidly rising human emissions of carbon dioxide might have initiated a feedback mechanism in the climate system, whereby natural sinks become even more inefficient as the amount of the greenhouse gas increases in future.

  The research gives greater urgency to the maneuvering ahead of the Copenhagen summit.

  The study is the most comprehensive analysis to date of how economic changes and shifts in the way people use the land in the past five decades have affected the concentration of carbon dioxide in the atmosphere.

  “The global trends we are on with CO2 emissions from fossil fuels suggest that we’re heading towards 6C of global warming,” Le Quere said. “This is very different to the trend we need to be on to limit global climate change to 2C [the level required to avoid dangerous climate change].”

  That would require carbon dioxide emissions from all sources to peak between 2015 and 2020 and that the global per capita emissions be decreased to 1 tonne of carbon-dioxide by 2050. The average US citizen emits 19.9 tonnes a year.

  “Based on our knowledge of recent trends in CO2 emissions and the time it takes to change energy infrastructure around the world and on the response of the sinks to climate change and variability, the Copenhagen conference is our last chance to stabilize climate at 2C above preindustrial levels in a smooth and organized way,” Le Quere said. “If the agreement is too weak or if the commitments are not respected, we will be on a path to 5C or 6C.”

  Le Quere’s work, part of the Global Carbon Project, showed that carbon dioxide emissions from burning fossil fuels increased at an average of 3.4 percent a year between 2000 and last year compared with 1 percent a year in the 1990s.

  Despite the global economic downturn, emissions still increased by 2 percent last year. Most of the recent increase has come from China and India, though a quarter of their emissions are a result of trade with the West.

  Based on projected changes in GDP, the scientists said emissions for this year were expected to fall to 2007 levels, before increasing again next year.

  But Le Quere’s conclusion on the decline of the world’s carbon sinks is not universally accepted. Wolfgang Knorr, of the University of Bristol, England, recently published a study in Geophysical Research Letters, using similar data to Le Quere, where he argued that the natural carbon sinks had not noticeably changed.

  “Our apparently conflicting results demonstrate what doing cutting edge science is really like and just how difficult it is to accurately quantify such data,” Knorr said.

  Overall trends can be difficult to detect because of the climactic and other natural conditions affecting absorption of sinks.

  Le Quere said, however, her team’s analysis had been able to remove more of the noise in the data that is associated with the natural annual variability of carbon dioxide levels due to, for example, El Nino or volcanic eruptions.
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