Modeled dependence of climate feedback on CO2 and stratospheric aerosol forcing at different latitudes

[Geoengineering News]

https://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-25-0482.1/JCLI-D-25-0482.1.xml

Authors: Long Cao and Yu Fang

Online Publication: 07 July 2026

DOI: https://doi.org/10.1175/JCLI-D-25-0482.1

Abstract

The strength of climate feedback determines forcing efficacy (the amount of global mean surface air temperature change per unit of radiative forcing imposed). Previous studies have found that the strength, spatial pattern, and temporal evolution of climate feedback depend on the type, location, and magnitude of imposed forcing. In this study we use the NCAR CAM4 model coupled with a slab ocean component to examine individual climate feedbacks (Planck, albedo, lapse rate, water vapor, and cloud feedback) in response to both CO2 and stratospheric sulfate aerosol forcing imposed over either globe, low latitudes (30°S–30°N), or polar region (60°S–90°S and 60°N–90°N). Our simulations show that the efficacy of a globally uniform aerosol forcing is about 90% of that from CO2 forcing. The difference in albedo, water vapor, lapse rate, and cloud feedback between these two forcings all contribute to the difference in forcing efficacy. Simulations also show that forcing efficacy and climate feedback depend strongly on the latitudes where the forcing is imposed. For both CO2 and stratospheric aerosol, forcing imposed at the polar region produces an efficacy that is more than three times that of global forcing, and forcing imposed at low latitudes produces an efficacy that is about half that of global forcing. Differences in albedo, water vapor, lapse rate and cloud feedback contribute to the difference in forcing efficacy for low-latitude and polar forcing. The key factors underlying differences in climate feedbacks are different patterns of surface and vertical temperature changes between CO2 and stratospheric aerosol forcing, and between low-latitude and polar forcing. Our study contributes to a further understanding of climate response to different types of external forcings. It also advances our understanding of climate feedback to stratospheric aerosol injection method that is proposed to counteract anthropogenic global warming.

Source: AMSO