Contribution of Shorter-term Radiative Forcings of Aerosols and Ozone to Global Warming in the Last Two Decades

TL;DR

This study investigates the roles of aerosols, ozone, and greenhouse gases in recent global warming, highlighting the impact of short-term radiative forcings and the CRE mechanism on temperature trends and climate change understanding.

Contribution

It introduces a no-parameter physics model that accurately reproduces observed global surface temperature trends from 2000 to 2024, emphasizing the significance of aerosols and ozone.

Findings

UST warming trends in polar regions since 2002

Surface cooling in Antarctic since 2005 and Arctic since 2016

Model captures 76% of GMST variance and predicts future reversal

Abstract

This paper reports observations of regional and global upper stratosphere temperature (UST) and surface temperature, as well as various climate drivers including greenhouse gases (GHGs), ozone, aerosols, solar variability, snow cover extent, and sea ice extent (SIE). We strikingly found warming trends of 0.77(+/-0.57) and 0.69(+/-0.22) K/decade in UST at altitudes of 35-40 km in the Arctic and Antarctic respectively and no significant trends over non-polar regions since 2002. These UST trends provide fingerprints of decreasing and no significant trends in total GHG effect in polar and non-polar regions respectively. Correspondingly, we made the first observation of surface cooling trends in both the Antarctic since 2005 and the Arctic since 2016 once the SIE started to recover. But surface warming remains at mid-latitudes, which causes the recent rise in global mean surface temperature (GMST). These temperature changing patterns are consistent with the characteristics of the cosmic-ray-driven electron reaction (CRE) mechanism of halogen-containing GHGs (halo-GHGs) with larger destruction rates at higher latitudes. Moreover, the no-parameter physics model of warming caused by halo-GHGs reproduces closely the observed GMSTs from 2000 to 2024, including the almost no warming during 2000-2012 and the significant warming by 0.2-0.3 deg C during 2013-2023, of which 0.27 deg C was calculated to arise from the net radiative forcing of aerosols and ozone due to improved air quality. The results also show that the physics model captures 76% of the variance in the observed GMSTs, exhibiting a warming peak in October 2023 and predicting a gradual GMST reversal thereafter. The results from this study may greatly improve our understanding of global climate change and lead to the identifying of the correct major culprit for human contribution to changing the climate.