[counters]

The important, missing detail that breaks down this analogy is that we don't have a reference for a long period of vulcanism while anthropogenic emissions of greenhouse gases continue.

This is where the "termination shock" issue comes in. Given current CO2 emission rates, a 50 year geoengineering strategy would mask an additional 100-125 ppm of CO2 added to the atmosphere. If the geoengineering scheme was suddenly stopped, it's not entirely obvious what the response trajectory would be of the climate system.

[red75prime]

Yeah, stratospheric seeding is mostly a stopgap measure that needs to be used in conjunction with other geoengineering and political projects that strive to reduce/reverse CO2 emissions.

[counters]

And therein arises the "moral hazard" issue. There is a legitimate concern that geoengineering could abate some of the concern over climate change and lead to further delays to reduce GHG emissions. And this is a serious problem because while we might mask global temperature change with these Approaches, they don't help resolve issues like ocean acidification.