Additional climate impacts of overshoot scenarios

We are approaching the 1.5°C temperature goal of the Paris agreement at a worrisome pace. Achieving this global temperature goal is physically still possible but would require drastic greenhouse gas emission reductions as well as the deployment of some level of carbon dioxide removal. Most scenarios that limit global warming to 1.5°C by the end of the century experiment an overshoot – a temporary exceedance of this level of global warming followed by a decrease in global mean temperature once global greenhouse gas emissions become net-negative in the second half of the century.

However, besides a number of well documented tipping points our understanding of the reversibility of climate impacts remains limited. It is indeed not well understood for which climate and sectoral impacts one can expect reversibility or not, and over which time scale it would occur.

Here we attempt to present an overview of changes that an overshoot would bring to the climate system. We analyze standard climate indicators as well as extreme event indicators in overshoot scenarios including the SSP119 and the SSP534 scenarios for a range of CMIP6 models. Comparing climate projections at a fixed warming level before and after global warming has peaked reveals significant differences in local climatic conditions, with precipitation pattern changes being particularly affected. This preliminary investigation will help to identify regions of interest for which the mechanisms that hinder reversibility could be analyzed in more depth in future research.