It does not automatically follow, of course, that this methane will in fact actually be released over such a time period. While not discounting the concerns, several scientists have argued that the ten-year timeline is far too short, prompting Wadhams to defend the scenario. NASA's Gavin Schmidt is among those who have been particularly critical of the notion of such a rapid methane pulse.
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Using an updated version of a model first used in the UK government's 2006 Stern Review on the Economics of Climate Change, the authors superpose a decade-long pulse of 50 Gt of methane, released into the atmosphere between 2015 and 2025, on two standard emissions scenarios: "business-as-usual," in which emission of CO2 and other greenhouse gases continues without mitigation; and a "low-emissions" case, in which there is a 50 percent chance of keeping the rise in global mean temperatures below 2 degrees Celsius (3.6 F).
They conclude that such a methane pulse would 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. 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)."