Constraining human contributions to observed warming since the pre-industrial period

Abstract

Parties to the Paris Agreement agreed to holding global average temperature increases "well below 2 degrees C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees C above pre-industrial levels". Monitoring the contributions of human-induced climate forcings to warming so far is key to understanding progress towards these goals. Here we use climate model simulations from the Detection and Attribution Model Intercomparison Project, as well as regularized optimal fingerprinting, to show that anthropogenic forcings caused 0.9 to 1.3 degrees C of warming in global mean near-surface air temperature in 2010-2019 relative to 1850-1900, compared with an observed warming of 1.1 degrees C. Greenhouse gases and aerosols contributed changes of 1.2 to 1.9 degrees C and -0.7 to -0.1 degrees C, respectively, and natural forcings contributed negligibly. These results demonstrate the substantial human influence on climate so far and the urgency of action needed to meet the Paris Agreement goals.