Concrete actions to curtail greenhouse gas emissions have so far been limited on a global scale1, and therefore the ultimate magnitude of climate change in the absence of further mitigation is an important consideration for climate policy2. Estimates of fossil fuel reserves and resources are highly uncertain, and the amount used under a business-as-usual scenario would depend on prevailing economic and technological conditions. In the absence of global mitigation actions, five trillion tonnes of carbon (5 EgC), corresponding to the lower end of the range of estimates of the total fossil fuel resource3, is often cited as an estimate of total cumulative emissions4, 5, 6. An approximately linear relationship between global warming and cumulative CO2 emissions is known to hold up to 2 EgC emissions on decadal to centennial timescales7, 8, 9, 10, 11; however, in some simple climate models the predicted warming at higher cumulative emissions is less than that predicted by such a linear relationship8. Here, using simulations12 from four comprehensive Earth system models13, we demonstrate that CO2-attributable warming continues to increase approximately linearly up to 5 EgC emissions. These models simulate, in response to 5 EgC of CO2 emissions, global mean warming of 6.4–9.5 °C, mean Arctic warming of 14.7–19.5 °C, and mean regional precipitation increases by more than a factor of four. These results indicate that the unregulated exploitation of the fossil fuel resource could ultimately result in considerably more profound climate changes than previously suggested.
Tuesday, May 24, 2016
10 Degrees in Two Hundred Years?
I suppose a couple of cautions are in order: I haven't seen any of the big names in climate science comment on this yet, and one of the authors is a Greens politician; but still, this seems an interesting look at what may happen if you were to burn all fossil fuel reserves. The abstract: