Climate mitigation pathways exploring end-of-century temperature targets often allow for a certain temperature overshoot, meaning that the global temperature is allowed to temporarily exceed the given target. The extent of this temperature overshoot is determined by many uncertain variables associated with the transformation of human systems, including those on socio-economic and technological progress. However, little is known about the additional climate risks that the associated temperature overshoot may pose.
The study now published in Nature Climate Change shows how, in the second half of the century, temperature overshoot will lead to both higher mitigation costs and higher economic losses. The research highlights the need to complement low-carbon climate mitigation pathway studies with climate risk analysis, in particular associated with the allowed temperature overshoot.
Ensemble of nine global models
The study, led by the European Institute on Economics and the Environment (EIEE), involved computing the probabilistic impacts for different warming targets and overshoot levels on the basis of an ensemble of nine global integrated assessment models. These are widely used to assess global climate change mitigation pathways, and all possess a detailed representation of energy and land-use systems and a wide array of decarbonization options. Among the nine models is the TIAM-ECN model operated by Bob van der Zwaan's team at TNO, with Larissa Nogueira and Francesco Dalla Longa as main modellers.
According to the researchers, a proper risk analysis accompanying proposed mitigation efforts can limit temperature overshoot. This will result in a stream of climate change benefits, cut major impacts and eventually lower mitigation costs. All these benefits accrue during the second half of the century.
The work also provides a bridge between the mitigation pathways community, which typically explores the costs and risks associated with the energy transition (in society), and the climate impact community, which investigates the costs and risks of climate change (in the environment).
Laurent Drouet et.al.: Net zero-emission pathways reduce the physical and economic risks of climate change. 2021, Nature Climate Change, DOI: 10.1038/s41558-021-01218-z