5 degrees Celsius as the maximally acceptable warming level.
(3) The study was led by the two brothers Malte and Nicolai Meinshausen from the Potsdam Institute for Climate Impact Research and Oxford University’s Statistics Department, respectively.
(4) More than 300 billion tonnes of carbon dioxide have been emitted since year 2000 due to burning of fossil fuels and deforestation. Thus, the emission budget of 1,000 billion tonnes (GtCO2) for the years 2000 up to 2050 is reduced to less than 700 billion tonnes for the remaining period since 2009. This remaining budget is hence less than a quarter of our estimate for known economically recoverable fossil fuel reserves (2800 GtCO2). See Meinshausen et al. (2009) for further details.
(5) IPCC Fourth Assessment Report, Intergovernmental Panel on Climate Change, http://www.ipcc.ch/ipccreports/assessments-reports.htm
(6) Companion study: 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. Nature, doi:10.1038/nature08019 (2009).
(7) Associated Commentary: Allen, M. R., Frame, D. J., Frieler, K., Hare, W., Huntingford, C., Jones, C., Knutti, R., Lowe, J., Meinshausen, M., Meinshausen, N. & Raper, S. The exit strategy: Emission targets must be placed in the context of a cumulative carbon budget if we are to avoid dangerous climate change. Nature Reports Climate Change, doi:10.1038/climate.2009.38 (2009).
(8) News & Views piece in Nature by Schmidt, G. & Archer, D. Too much of a bad thing. Nature (2009).