On the Linearity of External Forcing Response in Solar Geoengineering Experiments

[ayesha iqbal]

goo.gl/scholar/NCKxvJ

J. G. Virgin, C. G. Fletcher

November 16, 2022

Abstract

To assess impacts of solar geoengineering, the GeoMIP G1 experiment forces Earth System Models with prescribed reductions in solar radiation to balance increases in atmospheric CO2. One key source of uncertainty is the magnitude of solar constant reduction required to offset a CO2 quadrupling. Here, we decompose the G1 experiment in the Community Earth System Model with solar only and CO2 only forcing experiments to quantify single forcing rapid radiative adjustments. We find that radiative adjustments to both single forcings have a net positive effect on top of atmosphere energy balance such that they both increase the net G1 forcing. Stratospheric temperature and short-wave cloud adjustments are the main sources of positive adjustment in both Solar and CO2 scenarios. We also show that net G1 radiative adjustment cannot be represented linearly with CO2 and solar forcing adjustments, which is primarily traced to further reductions in boundary layer clouds.

Source: Geophysical research letters

[ayesha iqbal]

Poster's note: Revised Version 

DOI: 10.1029/2022GL100200

Abstract 

As an idealized proxy for solar geoengineering, the GeoMIP G1 experiment forces Earth System Models with prescribed reductions in solar radiation to balance increases in atmospheric CO2. One key source of uncertainty is the magnitude of solar constant reduction required to offset a CO2 quadrupling. Here, we employ single-forcing simulations with Community Earth System Model to decompose the distinct radiative adjustments associated with solar and CO2 forcing in the G1 experiment. We find that radiative adjustments  to both single forcings have a net positive effect on top of atmosphere energy balance such that they both increase the net G1 forcing. Stratospheric temperature and shortwave cloud adjustments are the main sources of positive adjustment in both Solar and CO2 simulations. We also show that net radiative adjustment in G1 cannot be represented linearly with CO2 and solar forcing adjustments, which is primarily traced to reductions in boundary layer clouds.

Source: Geophysical Research Letters