Hemispherically symmetric strategies for stratospheric aerosol injection

<p<Stratospheric aerosol injection (SAI) comes with a wide range of possible design choices, such as the location and timing of the injection. Different stratospheric aerosol injection strategies can yield different climate responses; therefore, understanding the range of possible climate outc...
Ausführliche Beschreibung

<p<Stratospheric aerosol injection (SAI) comes with a wide range of possible design choices, such as the location and timing of the injection. Different stratospheric aerosol injection strategies can yield different climate responses; therefore, understanding the range of possible climate outcomes is crucial to making informed future decisions on SAI, along with the consideration of other factors. Yet, to date, there has been no systematic exploration of a broad range of SAI strategies. This limits the ability to determine which effects are robust across different strategies and which depend on specific injection choices. This study systematically explores how the choice of SAI strategy affects climate responses in one climate model. Here, we introduce four hemispherically symmetric injection strategies, all of which are designed to maintain the same global mean surface temperature: an annual injection at the Equator (EQ), an annual injection of equal amounts of SO<span class="inline-formula"<<sub<2</sub<</span< at 15° N and 15° S (15N<span class="inline-formula"<+</span<15S), an annual injection of equal amounts of SO<span class="inline-formula"<<sub<2</sub<</span< at 30° N and 30° S (30N<span class="inline-formula"<+</span<30S), and a polar injection strategy that injects equal amounts of SO<span class="inline-formula"<<sub<2</sub<</span< at 60° N and 60° S only during spring in each hemisphere (60N<span class="inline-formula"<+</span<60S). We compare these four hemispherically symmetric SAI strategies with a more complex injection strategy that injects different quantities of SO<span class="inline-formula"<<sub<2</sub<</span< at 30° N, 15° N, 15° S, and 30° S in order to maintain not only the global mean surface temperature but also its large-scale horizontal gradients. All five strategies are simulated using version 2 of the Community Earth System Model with the middle atmosphere version of the Whole Atmosphere Community Climate model, version 6, as the atmospheric component, CESM2(WACCM6-MA), with the global warming scenario, Shared Socioeconomic Pathway (SSP)2-4.5. We find that the choice of SAI strategy affects the spatial distribution of aerosol optical depths, injection efficiency, and various surface climate responses. In addition, injecting in the subtropics produces more global cooling per unit injection, with the EQ and the 60N<span class="inline-formula"<+</span<60S cases requiring, respectively, 59 % and 50 % more injection than the 30N<span class="inline-formula"<+</span<30S case to meet the same global mean temperature target. Injecting at higher latitudes results in larger Equator-to-pole temperature gradients. While all five strategies restore Arctic September sea ice, the high-latitude injection strategy is more effective due to the SAI-induced cooling occurring preferentially at higher latitudes. These results suggest trade-offs wherein different strategies appear better or worse, depending on which metrics are deemed important.</p< Ausführliche Beschreibung

Autor*in:	Y. Zhang [verfasserIn] D. G. MacMartin [verfasserIn] D. Visioni [verfasserIn] E. M. Bednarz [verfasserIn] B. Kravitz [verfasserIn]

Format:	E-Artikel
Sprache:	Englisch

Erschienen:	2024

Übergeordnetes Werk:	In: Earth System Dynamics - Copernicus Publications, 2011, 15(2024), Seite 191-213
Übergeordnetes Werk:	volume:15 ; year:2024 ; pages:191-213

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DOI / URN:	10.5194/esd-15-191-2024

Katalog-ID:	DOAJ098588117