Fossil-fuel constraints on global warming

In 2008 and 2009 two papers by Kharecha and Hansen and by Nel and Cooper examined possible fossil energy availability and energy consumption scenarios and consequences for future climate. The papers yield somewhat similar results regarding atmospheric CO₂ levels, but they reach substantially different conclusions regarding future climate change. Here, we compare their methods and results. Our work shows that Nel and Cooper's paper significantly underestimates future warming. Nel and Cooper conclude that even if all the available fossil fuels would be burned at the maximum possible rate during this century, the consequent warming would cap at less than 1 °C above the 2000 level. We find that – under Nel and Cooper's assumption of an intensive exploitation of fossil fuels – the global temperature in 2100 will likely reach levels which would lead to severely damaging long-term impacts.