WADHAMS. Peter Wadhams (professor of Ocean Physics, and Head of the Polar Ocean Physics Group in the Department of Applied Mathematics and Theoretical Physics, 90-Nobel-Laureate University of Cambridge, UK) and colleagues on the threat of 50Gt methane from East Siberian Arctic Shelf (2013): “Economic time bomb. As the amount of Arctic sea ice declines at an unprecedented rate, the thawing of offshore permafrost releases methane. A 50-gigatonne (Gt) reservoir of methane, stored in the form of hydrates, exists on the East Siberian Arctic Shelf. It is likely to be emitted as the seabed warms, either steadily over 50 years or suddenly. Higher methane concentrations in the atmosphere will accelerate global warming and hasten local changes in the Arctic, speeding up sea-ice retreat, reducing the reflection of solar energy and accelerating the melting of the Greenland ice sheet. The ramifications will be felt far from the poles… To quantify the effects of Arctic methane release on the global economy, we used PAGE09. This integrated assessment model calculates the impacts of climate change and the costs of mitigation and adaptation measures… The methane pulse will bring forward by 15–35 years the average date at which the global mean temperature rise exceeds 2°C above pre-industrial levels — to 2035 for the business-as-usual scenario and to 2040 for the low-emissions case (see 'Arctic methane'). This will lead to an extra $60 trillion (net present value) of mean climate-change impacts for the scenario with no mitigation, or 15% of the mean total predicted cost of climate-change impacts (about $400 trillion)."(Gail Whiteman, Chris Hope and Peter Wadhams, “Vast costs of Arctic change”, Nature, 499, 25 July 2013: http://www.nature.com/nature/journal/v499/n7459/pdf/499401a.pdf and http://www.nature.com/nature/journal/v499/n7459/full/499401a.html ) .
[Editor’s note: The Global Warming Potential (GWP) of CH4 on a 20 year time frame and with aerosol impacts considered is 105 times that of CO2 [Drew T. Shindell , Greg Faluvegi, Dorothy M. Koch , Gavin A. Schmidt , Nadine Unger and Susanne E. Bauer , “Improved Attribution of Climate Forcing to Emissions”, Science, 30 October 2009: Vol. 326 no. 5953 pp. 716-718: http://www.sciencemag.org/content/326/5953/716 and Shindell et al (2009), Fig.2: http://www.sciencemag.org/content/326/5953/716.figures-only ). The German WBGU (2009) and the Australian Climate Commission (2013) have estimated that no more than 600 billion tonnes of CO2 can be emitted between 2010 and zero emissions in 2050 if the world is to have a 75% chance of avoiding a catastrophic 2C temperature rise (WBGU, “Solving the climate dilemma: the budget approach”: http://www.ecoequity.org/2009/10/solving-the-climate-dilemma-the-budget-approach/ and Australian Climate Commission, “The critical decade 2013: a summary of climate change science, risks and responses”, 2013, p7: http://climatecommission.gov.au/wp-content/uploads/The-Critical-Decade-2013-Summary_lowres.pdf ).. The 50 Gt (billion tonnes) CH4 in the East Siberian Arctic Shelf is thus equivalent to 50 billion tonnes CH4 x 105 tonnes CO2-equivalent/tonne CH4 = 5,250 tonnes CO2-e or about nine (9) times more than the world’s terminal greenhouse gas (GHG) pollution budget. We are doomed unless we can stop this Arctic CH4 release.]