A new study, involving academics at the University of Sheffield, has accurately measured for the first time the current carbon cycles in the world. The research will enable scientists to make more accurate predictions concerning the impact of climate change in the future.
The paper, which will be published today (5 July 2010) in the journal Science, used large amounts of remote sensing, climate and carbon data from around the world to assess Gross Primary Production. This is the process which drives all plant growth, food production, eco-system services and fluxes of carbon dioxide in the atmosphere.
The new approach measures for the first term the quantity and uncertainty of this large annual flux in carbon dioxide, from the atmosphere into plants, at 123 plus or minus 8 billion tonnes per year. The research also highlighted that uptake of carbon dioxide is most pronounced in the planet's tropical forests, which are responsible for 34% of the inhalation of carbon dioxide from the atmosphere. In addition, savannahs account for 26% of the global uptake, although they also occupy almost twice as much surface area as tropical forests.
It was also found that precipitation plays a significant role in determining the gross global carbon dioxide uptake on more than 40% of vegetated lands, a discovery that stresses the importance of water availability for food security. According to this study, Earth System models can show great variation and some of them overestimate the influence of rainfall on global carbon dioxide uptake.
The researchers used data from FLUXNET, an international initiative established more than 10 years ago to monitor exchanges of carbon dioxide between the Earth's ecosystems and the atmosphere, along with remote sensing and climate data from around the world to calculate the spatial distribution of mean annual Gross Primary Production between 1998 and 2006.
The international collaboration involved Dr Mark Lomas and Professor Ian Woodward, from the University of Sheffield's Department of Animal and Plant Sciences, and was led by Christian Beer and Markus Reichstein from the Max Planck Institute for Biogeochemistry in Jena, Germany. The Sheffield-based researchers used a global vegetation model developed in the city to simulate global scale productivity. The model concurred with independent data and a key result was the global scale mapping of precipitation limitations of productivity.
Professor Ian Woodward said: "This model indicates that these limitations of productivity will become more intense with global warming, while at the same time indicating that some areas which are temperature limited at high latitudes will show increased productivity."
Journal
Science