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Since we're past the point where emissions cuts alone can keep long term warming below 2 C, I do expect active geoengineering efforts later this century. Solar
by philipkglass 10y ago
Since we're past the point where emissions cuts alone can keep long term warming below 2 C, I do expect active geoengineering efforts later this century. Solar radiation management with aerosols is not a long term fix but could keep positive feedback effects damped while slower long term fixes (like emissions reduction plus accelerated silicate weathering) roll out.
The attractive thing about sulfate aerosols is that they could be formed from sulfur dioxide, which is cheap to form via sulfur combustion and disperses excellently because it's a gas. Delayed oxidation reactions cause SO2 to form nuclei for aerosols. Even though calcium carbonate is also inexpensive, I don't think there is a comparably cheap/easy way to deliver a fluid precursor for it to the upper atmosphere. The closest I can think of is aerosolizing a calcium hydroxide solution that would carbonate in situ via reaction with atmospheric CO2... but calcium hydroxide is only slightly soluble in water. You'd need to lift a lot of extra water mass.
- marcosdumay 10y ago> The attractive thing about sulfate aerosols is that they could be formed from sulfur dioxide So, it just a matter of throwing tons of "dry sulfuric acid" on the atmosphere?
- philipkglass 10y agoSort of. One could release sulfur dioxide (or burn sulfur to form sulfur dioxide) at high altitude, or release slower-reacting sulfur species like carbonyl sulfide from surface locations. In any of these cases what will happen is that reactions with nitrogen oxides, ozone, light, atmospheric moisture, and other particles will ultimately convert the sulfur to sulfuric acid, which will then form additional particles of high reflectivity. It would somewhat increase the surface precipitation acid burden, similar to the acid rain that was a byproduct of 20th century industrialization, but most sulfur oxides that come from power plants or metal refining are flushed out of the lower atmosphere by precipitation. By directly or indirectly adding SO2 to the stratosphere instead of the troposphere, the ratio of reflection:acid content would be higher than that of incidentally produced waste-product SO2. (That's why we can't start cooling the planet just by removing sulfur controls from existing coal plants; most of that SO2 would produce acid rain accompanied by little additional sunlight reflection.)
- tbrownaw 10y agopast the point where emissions cuts alone can keep long term warming below 2 C Isn't that 2C supposed to have come from "just give me a damn number" rather than any analysis of likely impacts? I'm going to be very amused if we somehow stop any warming without reducing co2, and die off when all the shellfish keep dissolving.
- philipkglass 10y agoYes, it's a pretty arbitrary number: https://www.carbonbrief.org/two-degrees-the-history-of-climate-changes-speed-limit https://www.carbonbrief.org/two-degrees-the-history-of-clima... I don't think that "amused" would exactly be my reaction if we kill off all the wild shellfish :-/