Political choices that delay efforts to mitigate climate change have the largest impact on the cost of trying to meet global warming targets, according to an analysis in this week’s Nature.

The study considers four key factors that can affect the costs of staying below a certain global warming threshold, such as 2 °C. These findings could have important implications for ongoing climate policy discussions.

Poor understanding of the costs of climate change mitigation is underpinned by uncertainties in the geophysical response of the Earth system to emissions of greenhouse gases, availability of mitigation technology, social demand for energy and political decision-making. Usually the geophysical uncertainties are assessed separately from the other three, but Joeri Rogelj and colleagues integrate all four factors in an assessment of the overall influence of these dimensions. They find that political uncertainties are the most influential, followed by geophysical, social and technology uncertainties. To achieve climate change targets, the implementation of sustained, concerted and coordinated mitigation efforts must not be delayed, the authors conclude.