[eesmith]

If it were so easy then stratospheric aerosol injection would get the sulfur up high enough to be more effective, without the harm of bunker fuel pollution.

From https://en.wikipedia.org/wiki/Global_dimming

> Because the historical levels of global dimming were associated with high mortality from air pollution and issues such as such as acid rain,[123] the concept of relying on cooling directly from pollution has been described as a "Faustian bargain" and is not seriously considered by modern research.[111] Instead, the seminal 2006 paper by Paul Crutzen suggested that the way to avoid increased warming as the sulfate pollution decreased was to revisit the 1974 proposal by the Soviet researcher Mikhail Budyko.[124][125] The proposal involved releasing sulfates from the airplanes flying in the upper layers of the atmosphere, in what is now described as stratospheric aerosol injection, or SAI.[122] In comparison, most air pollution is in the lower atmospheric layer (the troposphere), and only resides there for weeks. Because aerosols deposited in the stratosphere would last for years, far less sulfur would have to be emitted to result in the same amount of cooling.