The Great Transition
2000 and 2006, 264 Gt CO2 were emitted – this means if rates of CO2are kept at their current rate of 36.3Gt per year, the total carbon budget would be exhausted by 2024 or 2027 depending on the accepted probability of exceeding 2 °C (20 per cent and 25 per cent respectively). However, the authors also warn that if global greenhouse gas emissions are still more than 25 per cent above 2000 levels in 2020, the probability of exceeding 2°C rises 53–87 per cent. Given that 80 per cent of greenhouse gases are due to the combustion of CO2, this means limiting use to less than one half of the proven economically recoverable oil, gas and coal reserves. Using a different methodology, the second paper led by Myles Allen, Head of the Climate Dynamics group at University of Oxford’s Atmospheric, Oceanic and Planetary Physics Department yields results that are broadly consistent with Meinshausen.106 More recent work still from the Met Office Hadley Centre warns of a scenario in which a 4°C rise in temperature by 2060 is possible. In 2008, cautious calculations by nef’s climate change and energy programme suggest that there may be as little as 100 months, starting from August 2008, to stabilise concentrations of greenhouse gases in the atmosphere – before the risk of uncontrollable global warming occurring increases significantly.107 This has also been supported by the recent research by the Tyndall Centre for Climate Change Research.108
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