Scientists present new challenges for climate change policy - 29 April 2009
Two studies published in Nature on 30 April show that the risk of dangerous climate change is primarily determined by the accumulation of carbon dioxide emissions over time, not by short-term emission rates.
The first study led by Dr Myles Allen from Oxford University, and involving Dr Chris Huntingford from the Centre for Ecology & Hydrology, shows that total cumulative emissions of one trillion tonnes of carbon (1 Tt C, or 3,670 billion tonnes of CO2) over the entire anthropocene period 1750-2500 causes a most likely peak warming of 2 degrees Celsius above pre-industrial temperatures. Most of the world’s governments are committed to avoiding warming in excess of 2 degrees Celsius. Of this budget, emissions to 2008 have already consumed approximately half (0.5 Tt C).
The second study, led by Dr Malte Meinshausen from the Potsdam Institute for Climate Impacts Research, finds that a total emission budget of about 0.9 Tt C gives a best-estimate peak warming by 2100 of 2 degrees Celsius, including the effects of other human influences on climate. This budget drops to less than ¾ Tt C (equivalent to 1,000 billion tonnes of CO2 between 2000 and 2050) if the risk of temperatures exceeding 2oCelsius is limited to one-in-four.
Dr Myles Allen said, “To avoid dangerous climate change we will have to limit the total amount of carbon we inject into the atmosphere, not just the emission rate in any given year. Climate policy needs an exit strategy: as well as reducing carbon emissions now, we need a plan for phasing out net emissions entirely.”
Dr Chris Huntingford said,” Research often reveals new complexities, but this analysis could actually simplify matters for policymakers: the relationship between total emissions and future warming can be inferred largely from quantities we can observe, and is remarkably insensitive to the timing of future emissions.”
The research for the first study was carried out by scientists from the University of Oxford, the Centre for Ecology & Hydrology, the Met Office and Potsdam Institute for Climate Impacts Research.
Additional information
Allen, M. R., Frame, D. J., Huntingford, C., Jones, C. D., Lowe, J. A., Meinshausen, M. & Meinshausen, N. Warming caused by cumulative carbon emissions towards the trillionth tonne was published in Nature on 30 April 2009, doi:10.1038/nature08019
Media enquiries for Dr Chris Huntingford should be directed to the Centre for Ecology & Hydrology press office. Oxford University issued a press release to accompany publication of this paper.
Dr Chris Huntingford is a climate modeller based at the Centre for Ecology & Hydrology in Wallingford, UK.
Useful links
CEH's Biogeochemistry Science Programme
Research carried out by Dr Chris Huntingford
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