BTAS - There Is No Plan B - Why Albedo Hacking Is Insane Bullshit That Never Work
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The upshot is that the total cumulative carbon allocation for humanity compatible with a 50–50 chance of keeping global warming under 2 degrees Celsius (3.6 degrees Fahrenheit) is, in round numbers, a trillion tonnes. That’s it. Forever. And of that trillion tonnes, we have already used up over 630 billion tonnes, leaving just 370 billion tonnes to go.
That might seem like a lot of tonnes, but at current emissions rate, we’d get there in just 37 years, or 2057. Up until 2016, there was reason to hope that perhaps the world emission rate had stopped growing and had leveled off; if the emission rate held steady at that level out to 2030, and thereafter trended linearly to zero by 2080, then with the help of the Paris climate accords we would have decarbonized without exceeding the trillion-tonne budget.
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Albedo hacking has been touted as a sort of Plan B to make up for the world’s failure to make a responsible start on decarbonization of the economy. This is the scenario envisioned in an editorial by the noted atmospheric chemist Paul Crutzen in 2006, and it has tended to dominate the perception of the role of albedo hacking ever since (Crutzen 2006 Crutzen, P. 2006. “Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve A Policy Dilemma?” Climatic Change 77: 211–220. doi:10.1007/s10584-006-9101-y. August.[Crossref], [Web of Science ®] , [Google Scholar]). But of all the possible scenarios in which albedo hacking would be deployed, using it to make up for a failure to decarbonize is the most nonsensical. Carbon dioxide accumulates in the atmosphere, but stratospheric aerosols do not. Therefore, albedo hacking as a response to failure to decarbonize requires injecting ever-increasing amounts of chemicals into the stratosphere, up to the point where the physical limits of the technique are reached or unanticipated adverse consequences become unbearable.
The excess carbon dioxide that human activities inject into the atmosphere has a warming effect that extends essentially forever, whereas the stratospheric aerosols meant to offset that warming fall out of the atmosphere in about a year. It’s just a matter of gravity – stuff denser than its surroundings falls – aided a bit by atmospheric circulations that enhance the removal. This is why the cooling effects of even a major volcanic eruption like Pinatubo dissipate after two years or so. Hence, whatever level of albedo hacking is needed to avoid a dangerous level of warming must be continued essentially forever. Otherwise, an abrupt termination would catastrophically unleash pent-up warming in a matter of a few years – a snapback known as Termination Shock – and the magnitude of this potential climate shock would increase, the longer that albedo hacking is used to offset our failure to decarbonize. Deployment of albedo hacking does not in any way “buy time” to get carbon dioxide emissions under control, since once emitted, carbon dioxide cannot to any significant extent be unemitted with known economically feasible technology; if albedo modification becomes necessary, it must be maintained essentially forever. The problematic need to continue albedo hacking essentially forever, if it becomes necessary at all, is called the problem of Millennial Commitment.
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https://desdemonadespair.net/2019/09/there-is-no-plan-b-for-dealing-with-climate-change-with-regard-to-the-climate-crisis-yes-its-time-to-panic.html
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