#20: An Emissions Budget for Climate Safety

May 14, 2009
by phil
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In a recent Guardian newspaper poll, nine out of ten climate scientists said they did not believe political efforts to restrict average global warming to 2C would succeed. However, two new papers in the 30th April issue of Nature magazine show that it is still technically possible to conceive of an emissions trajectory that would make it likely (ie give us a 75% chance) that we would keep within 2C of global warming compared to pre-industrial times (the threshold defined by the EU between acceptable and dangerous climate change). However it is a tiny budget – less than a quarter of the remaining proven fossil fuel reserves. We speak to one of the lead authors of the studies – Myles Allen of the Climate Dynamics team, University of Oxford – to draw out some of the implications for national and international policymakers.

Key messages

  • We can release 1,000 GtCO2 between 2000-2050 if we want to have a 75% chance of staying below 2C
  • We have already used up a third of this budget (2000-2008)
  • Our remaining budget (700 GtC02) is equivalent to less than a quarter of the remaining proven fossil fuel reserves
  • James Hansen’s 350 ppmC02 scenario will give us a higher chance of staying below 2C since it is based on a lower emissions budget
  • An emissions budget should be the focus of the UN talks rather than a stabilization target (such as 350ppmCO2) or a long-term target (such as 50-85% global cut in CO2 by 2050)
  • The Alliance of Small Island States and the Least Developed Country blocs (together representing 100 countries and around 1 billion people) are calling for temperature rise to be limited to 1.5C rather than 2C

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