Stratospheric injection of solid particles could reduce climate change impacts

The increasingly dismal prospects of climate change mitigation have propelled research on SAI. The idea is to continuously inject aerosols or their precursors into the stratosphere, where they reflect more sunlight back to space, which cools the climate. SAI does not present a solution to climate change and can only treat some of its symptoms. However, SAI could potentially be used to temporarily reduce some of the impacts of climate change, for example by keeping global temperatures below 1.5 K warming until the net-zero goal has been reached.

To date most research on SAI has focused on the injection of SO₂, which after oxidation forms sulfuric acid aerosols. However, SAI via SO₂ would result in a number of adverse side effects such as local stratospheric warming due to absorption of radiation, which could disrupt the global atmospheric circulation, potentially even exacerbating impacts of climate change at a regional level.

Fabrice Stefanetti and his co-authors used an Earth system model incorporating a solid particle scheme to show that injection of solid particles such as alumina, calcite and diamond could minimize these side effects. The substantially reduced stratospheric heating reduces impacts on the general atmospheric circulation, stratospheric moistening, and on the thickness of the entire troposphere. As a result, solid particles also induce less residual warming over the Arctic, resulting in greater reduction of GHG-induced polar amplification compared to injection of SO₂.

The study highlights the advantages of SAI via non-absorbing materials such as diamond particles. However, substantial uncertainty abounds on other environmental impacts such as the stratospheric ozone response or aerosol-cloud interactions, which prompts new research to explore the full potential of alternative types of SAI in the portfolio of climate intervention measures.