The 10-year zonal average corresponds to the average total column ozone depletion resulting from the injection of 5 Mt/year of alumina particles assuming different settings of R1 or alumina particles to be coated with sulfuric acid (“H2SO4 coating”) simulated with SOCOL-AER in (a) 2020 and (b) 2090 ozone-depleting substances and greenhouse gas conditions. For comparison, we also show a SO2 injection scenario with injection rates equal to those of the alumina injection scenarios (i.e. 5 Mt of SO2 per year in red). Credit: Geophysical research letters (2023). DOI: 10.1029/2023GL105889
As levels of greenhouse gases rise in Earth’s atmosphere, scientists are considering ways to temporarily limit rising temperatures. One idea is to inject aerosols into the stratosphere to reflect incoming sunlight, thereby reducing global warming and its associated risks.
Most previous research has focused on the use of sulfur dioxide gas, also released during volcanic eruptions. However, injecting sulfur dioxide into the stratosphere is associated with side effects, including ozone depletion and local stratospheric warming.
Recent studies have shown that the use of solid materials such as alumina, calcite or even diamond particles could cool the climate more effectively while simultaneously reducing these side effects. However, understanding of how solids injection affects the stratospheric ozone layer is limited. Current knowledge is based on rare, decades-old experimental data on alumina particles emitted into the stratosphere via the exhaust of solid-fuel space rockets.
In new research published in Geophysical research letters, Sando Vattioni and colleagues show that stratospheric conditions resulting from space shuttle exhaust plumes are not comparable to alumina injection scenarios for climate intervention. They found that while alumina injection may have an advantage over sulfur dioxide in terms of reducing local stratospheric warming, there are “significant uncertainties” in estimating the impact of such injections on the ozone layer.
The scenarios tested would inject about 5 megatons of alumina particles into the stratosphere per year, which would offset about a quarter of the current radiative forcing caused by anthropogenic greenhouse gas emissions. The researchers estimate that the global average ozone loss from these scenarios could range from negligible to 9 percent, about twice the historic peak of ozone loss from chlorofluorocarbons in the 1990s.
The authors note that more research is needed on potential surface reactions of solid particles in the atmosphere. In particular, this means learning more about surface reactions under current and future stratospheric conditions with respect to temperature, trace gas concentrations and relative humidity. Improving this understanding could help reduce uncertainty about the potential behavior of solid particles when injected into the stratosphere for climate intervention purposes.
More information:
Sando Vattioni et al, Chemical impact of the injection of stratospheric alumina particles for the modification of solar radiation and associated uncertainties, Geophysical research letters (2023). DOI: 10.1029/2023GL105889
Provided by the American Geophysical Union
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