Climate change: Global temperatures might not respond to mitigation efforts for decades

Significant reductions in human emissions could take decades until they lead to detectable changes in global surface temperatures, a study in Nature Communications finds. These results suggest that climate change mitigation demands long-term commitment, as short-term effects cannot be expected.

While it is widely agreed that reductions in anthropogenic emissions are necessary to mitigate global warming, the timescale over which atmospheric changes may occur is unclear. In public debates it is sometimes assumed that reductions will rapidly affect global warming, but the climate system is characterized by strong inertia and intrinsic noise, which can hide a response to abrupt changes in the short-term. Although this issue has been discussed in previous studies of carbon dioxide (CO2) mitigation, the response to other human emissions is less well known.

Bjørn Samset and colleagues studied the effects of abrupt reductions in several types of emissions (such as CO2, methane and black carbon) in a modelling setup. As they use idealized emission reductions scenarios, the authors note that the timings in the study cannot be interpreted as predictions, but can provide an impression of the timescales over which changes will be detectable, despite the internal noise of the climate system. They find that for many emissions, including CO2, methane, nitrous oxide and different aerosols, it would take decades until a statistically measurable reduction can be detected in the global surface temperature. Although there is no detectable short-term response, mitigation of emissions including CO2, methane and black carbon, leads to substantially less warming on longer time scales. The authors conclude that the absence of short-term global temperature responses to mitigation should not be an argument against pursuing these efforts, as they need time to be effective.