Post AaC0QkvXYc8KsF838K by atthenius@fediscience.org
(DIR) More posts by atthenius@fediscience.org
(DIR) Post #AaC0QkvXYc8KsF838K by atthenius@fediscience.org
2022-12-26T03:03:57Z
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Several folks have been sharing news of a private company trying a #geoengineering approach to ‘cancel out’ some global warming.#SRM or solar resource management is humans trying to co-opt the way strato-volcanic eruptions impact the earth. #Volcano #climateHere is my summary on WHY I think this is a bad idea. (Think my colleagues would agree; please add on.) 1/
(DIR) Post #AaC0QmtqDtxkzYLilM by atthenius@fediscience.org
2022-12-26T03:07:02Z
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These Making Sunset guys are thinking of a SRM ~1 W/m2. Volcanic eruptions like 91 Mt Pinatubo are like 5-7 times that size at peak. 91 Pinatubo injected something like 18 Tg SO2 into the stratosphere and 150 Mt H2O. (Much Bigger!) 91 Pinatubo caused a peak decrease in global temperature of 0.5C. 1) Increasing the aerosol optical depth of the atmosphere with sulfate aerosols (or ash, dust or a whole host of other mostly non-absorbing aerosols) can decrease the temperature of the troposphere.
(DIR) Post #AaC0QoqMzmNH1Mjyd6 by atthenius@fediscience.org
2022-12-26T03:08:38Z
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2) It is pretty obvious that if sunlight or INcoming SOLar radiATION gets caught up with aerosols scattering back to space in the stratosphere, that there is cooling in the troposphere… but also some WARMING in the stratosphere … because some of the insolation won’t be scattered but absorbed.
(DIR) Post #AaC0QqfoC17AhBoZRg by atthenius@fediscience.org
2022-12-26T03:09:29Z
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3) Stratospheric chemistry is complex. The ozone layer is delicate. Messing with the temperature or chemical composition of the stratosphere, including injection of SO2 or H2O, can mess up ozone because of a chemical pathway impacting the destruction of ozone through OH radicals availability. Ozone in the stratosphere is good for people (skin cancer w/o it!)… and its destruction / creation also can cause regional temperature anomalies of a couple degrees C.
(DIR) Post #AaC0QrjOGBZdyaUwfQ by atthenius@fediscience.org
2022-12-26T20:07:45Z
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Adding a bit of clarifying to the comment about Making Sunset guys wanting to do ~1 W/m2 forcing. I have no idea what they actually did — I haven’t seen independent measurements. Maybe its only 10’s of grams SO2 like in the MIT techreview reporting. I say ~1W/m2 forcing because they tried to get someone from scientists’ geoengineering listserve to write up a white paper on the impact of a forcing that size.
(DIR) Post #AaC0QtHoTghendbwxc by atthenius@fediscience.org
2022-12-26T03:11:13Z
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4) Global temperatures and hydrologic cycle are linked. Increase stratospheric aerosols, and you decrease the amount of direct shortwave insolation reaching the earth’s surface. Evaporation occurs most readily with that direct shortwave insolation, so volcanic aerosols or SRM will inevitably also decrease shortwave to the earth’s surface and decrease evaporation. Precipitation and evaporation MUST balance to first order. IOW: SRM aerosols likely mean lower temperatures AND lower precipitation.
(DIR) Post #AaC0QvvwdRzd0gP1n6 by atthenius@fediscience.org
2022-12-26T03:12:18Z
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5) Volcanic / SRM clouds are ephemeral wispy things that do not cause uniform global changes. Any region (think an area of earth the size of Europe or Australia) can have the opposite impact of global trends. Some things that have been suggested for the year following a volcanoes (and thus also for SRM):: winter warming of Europe. Predilection for a positive El Nino Southern Oscillation state.
(DIR) Post #AaC0Qyg6Qo6TWQ0v0y by atthenius@fediscience.org
2022-12-26T03:13:15Z
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6) Because the impacts of stratospheric aerosols are not globally homogeneous, you can get weird but profound regional things. Like, in the past, volcanic activity in the Northern Hemisphere would cool that hemisphere preferentially, shifting global tropical rain bands called the ‘Inter-Tropical Convergence Zone’ into the southern hemisphere and depriving massive areas of the rain needed to have a ‘normal’ climate.
(DIR) Post #AaC0R1Rg8tLe6YHwRs by atthenius@fediscience.org
2022-12-26T03:13:34Z
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7) In human history, many of the greatest (most tragic) famines were associated with times of increased volcanism. Plants actually need shortwave radiation for photosynthesis. Its nice to be warm, but its better to have plant food. SRM could decrease crop yields and all sorts of things directly from the radiative changes (not to mention the precipitation and temperature changes from above).
(DIR) Post #AaC0R4Ox9TwzGy2J7I by atthenius@fediscience.org
2022-12-26T03:15:18Z
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8) Although there *are* natural examples of volcanoes… there aren’t THAT many. Empirical evidence for how volcanoes impact climate is extremely limited in the satellite era (1980-today); only 1991 Mt Pinatubo was observed mostly well. (1982 El Chichon less so… and its only ~⅓ the size of 91Pinatubo). We have models for how the climate will respond to forcing excess aerosols into the stratosphere, but relatively little constraint. SRM folks are forcing us all into uncharted territory.
(DIR) Post #AaC0R7V5d7dqsrvkbA by atthenius@fediscience.org
2022-12-26T03:15:28Z
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9) There are no geopolitical boundaries in the stratosphere. Stuff goes where the background circulation (brewer Dobson) and chemistry requires. The good part of that is that if the aerosols injected into the stratosphere are volcano-sized (~0.5 μm) and not TEENY, this circulation will remove stuff in 4-5 years, depending on size and level of injection.