The global warming projection for the end of the twenty-first century could be about 15 per cent greater than the steepest emissions scenario from the Intergovernmental Panel on Climate Change (IPCC), reports a study published in this week’s Nature.

Climate models indicate that human-caused emissions of greenhouse gases will continue to warm the global climate. However, the projected warming varies extensively among different climate models, complicating efforts to mitigate and adapt to climate change.

Patrick Brown and Ken Caldeira assess the many available climate models and constrain them with observational data of the energy budget at the top of Earth’s atmosphere. Focusing on those that realistically simulate observations, the authors find that the observationally informed warming projection to the end of the twenty-first century for the steepest emissions scenario is about 15 per cent warmer than reported by the IPCC and the uncertainty of the previous projections is reduced by a third.

The results add to a broadening collection of research indicating that when models are constrained by observations, they tend to project more global warming for the remainder of the twenty-first century. Therefore, achieving any given global temperature stabilization target will require steeper greenhouse gas emissions reductions than previously calculated.