Estimating the timing of geophysical commitment to 1.5 and 2.0 °C of global warming

Following abrupt cessation of anthropogenic emissions, decreases in short-lived aerosols would lead to a warming peak within decade, followed by slow cooling as GHG concentrations decline. This implies geophysical commitment temporarily crossing levels before reaching them. Here we use an emissions-based climate model (FaIR) estimate temperature change following emissions 2021 and every year thereafter until 2080 eight Shared Socioeconomic Pathways (SSPs). Assuming medium-emissions trajectory (SSP2–4.5), find that are already committed greater than 1.5 °C with 42% probability, increasing 66% 2029 (340 GtCO2 relative 2021). Probability 2.0 is currently 2%, 2057 (1,550 Because will cool from decline, 2100 not occur at least probability 2055. Halting does immediately stop atmospheric continue warm the planet. study shows society may be exceeding probability; delaying cuts increases this for all scenarios.