Abstract
Solar geoengineering refers to a range of proposed methods for counteracting global warming by artificially reducing sunlight at Earth’s surface. The most widely known solar geoengineering proposal is stratospheric aerosol injection (SAI), which has impacts analogous to those from volcanic eruptions. Observations following major volcanic eruptions indicate that aerosol enhancements confined to a single hemisphere effectively modulate North Atlantic tropical cyclone (TC) activity in the following years. Here we investigate the effects of both single-hemisphere and global SAI scenarios on North Atlantic TC activity using the HadGEM2-ES general circulation model and various TC identification methods. We show that a robust result from all of the methods is that SAI applied to the southern hemisphere would enhance TC frequency relative to a global SAI application, and vice versa for SAI in the northern hemisphere. Our results reemphasise concerns regarding regional geoengineering and should motivate policymakers to regulate large-scale unilateral geoengineering deployments.
Highlights
Solar geoengineering refers to a range of proposed methods for counteracting global warming by artificially reducing sunlight at Earth’s surface
We investigate North Atlantic tropical cyclone (TC) in simulations performed using the HadGEM2-ES general circulation models (GCMs) in a fully coupled atmosphere–ocean configuration[18] by directly tracking TC-like features[19], by utilising various metrics that have been developed as proxies for TC activity[13,20,21], and by employing a widely used statistical-dynamical downscaling model[22]
The injection of aerosol into the stratosphere following a volcanic eruption can lead to radically different spatial and temporal distributions depending upon the altitude and latitude of the injection[30], the representation of the quasi-biennial oscillation (QBO31) and the local meteorological conditions that prevail at the time of the eruption[32]
Summary
Solar geoengineering refers to a range of proposed methods for counteracting global warming by artificially reducing sunlight at Earth’s surface. We investigate the effects of both single-hemisphere and global SAI scenarios on North Atlantic TC activity using the HadGEM2-ES general circulation model and various TC identification methods. A study has been performed[6] on the frequency and intensity of Atlantic hurricanes and associated storm surges using a multimodel analysis of Geoengineering Model Intercomparison Project (GeoMIP) scenarios G3 and G47, where stratospheric aerosol injection (SAI) is applied relatively uniformly to both hemispheres. As regional SAI applications have been proposed to target, for instance, NH sea-ice concentrations[8] and would necessarily alter the inter-hemispheric aerosol gradient, it is instructive to assess the implications of global and regional SAI scenarios on North Atlantic TC activity. Note that on top of these TC identification methods, other methods have been developed such as ‘dynamical downscaling’ that involves embedding a high-resolution climate model within a GCM26, and alternative explicit TC identification algorithms such as the Camargo-Zebiak algorithm[27]
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