Fossil fuels dominate future warming but not the past or present

Nathaniel Tarshish, David M Romps, Inez Fung

Fossil fuels have long been considered the primary driver of global warming, but this claim has not been rigorously demonstrated. Here, we quantify the impact of fossil fuels on historical warming with an ensemble of climate emulators that account for aerosol cooling and other key uncertainties. Contrary to conventional wisdom, we find that the majority of present-day anthropogenic warming likely stems from non-fossil sources, particularly agriculture and land-use change. Moreover, fossil fuels likely caused net cooling before 1980, as high rates of sulfate emissions from coal increased Earth's reflectivity enough to offset the associated greenhouse-gas warming. Although fossil fuels are likely responsible for less than half of present-day warming, they have dominated emissions of long-lived carbon dioxide, and so fossil fuels are expected to dominate global warming by mid-century and for millennia thereafter.