Rapid and extensive warming following cessation of solar radiation management

Kelly E Mccusker,Kyle C Armour,David S Battisti,Cecilia M Bitz

doi:10.1088/1748-9326/9/2/024005

Abstract

Solar radiation management (SRM) has been proposed as a means to alleviate the climate impacts of ongoing anthropogenic greenhouse gas (GHG) emissions. However, its efficacy depends on its indefinite maintenance, without interruption from a variety of possible sources, such as technological failure or global cooperation breakdown. Here, we consider the scenario in which SRM—via stratospheric aerosol injection—is terminated abruptly following an implementation period during which anthropogenic GHG emissions have continued. We show that upon cessation of SRM, an abrupt, spatially broad, and sustained warming over land occurs that is well outside 20th century climate variability bounds. Global mean precipitation also increases rapidly following cessation, however spatial patterns are less coherent than temperature, with almost half of land areas experiencing drying trends. We further show that the rate of warming—of critical importance for ecological and human systems—is principally controlled by background GHG levels. Thus, a risk of abrupt and dangerous warming is inherent to the large-scale implementation of SRM, and can be diminished only through concurrent strong reductions in anthropogenic GHG emissions.

Highlights

Stratospheric aerosol injection has emerged as a popular, hypothetical solar radiation management (SRM) technique due to its technological and economic feasibility and potential to swiftly and effectively cool the planet and avoid impending climate emergencies (Keith et al 2010, Vaughan and Lenton 2011)
These results follow from only a few key aspects of climate: the rapid increase in radiative forcing that would occur upon SRM cessation; the rapid adjustment timescales of the ‘fast’ components of the climate system, such as land (Held et al 2010); and the relatively small climate variability of the past century, within the tropics
The results presented here reinforce and extend this assessment by (i) quantifying the regional and seasonal climate response to SRM cessation, of critical importance for the impacts on ecological and human systems, and (ii) demonstrating that over a wide range of plausible 21st century scenarios, rates of warming are primarily controlled by the accumulated greenhouse gas (GHG) emissions that are abruptly unmasked upon SRM cessation

Summary

Introduction

Stratospheric aerosol injection has emerged as a popular, hypothetical solar radiation management (SRM) technique due to its technological and economic feasibility and potential to swiftly and effectively cool the planet and avoid impending climate emergencies (Keith et al 2010, Vaughan and Lenton 2011). (Wigley 2006, Matthews et al 2007, Ross and Matthews 2009, Brovkin et al 2009, Robock et al 2008, McCusker et al 2012, Irvine et al 2012) have focused on the global and annual mean climate response under ‘business-as-usual’ GHG emissions scenarios These studies suggest that the rates of global warming following SRM cessation could reach 1 ◦C/decade or greater, far exceeding warming rates had no SRM been implemented. Motivated by the above assessments of impacts of rapid change on ecosystems and human systems, we first consider here the geographic structure of temperature and precipitation change following SRM cessation, with particular focus on the rates of seasonal warming over land, features lost in the global and temporal averaging of earlier studies. The results are considered in the context of the temperature and precipitation trends experienced over the past century, to which ecosystems and human systems have become well adapted in their respective regions

Geographic pattern of land surface temperature trends

Findings

Discussion and conclusions