4:00 start of my talk 9:30 start of 2 Wm^-2 scenario description 30:50 end of scenario 44:00 start of napkin diagram (mitigation, CDR, and SRM)

Background papers: Moderate & Temporary SRM: keith.seas.harvard.edu/publications/t… Climate response: keith.seas.harvard.edu/publications/h… SCoPEx: keith.seas.harvard.edu/publications/s… and projects.iq.harvard.edu/keutschgroup/s…

Great talk. But you appear to seriously overestimate the incentives and ease of doing multilateral agreements to implement this technology. You say that going alone is more risky than teaming up - ergo teaming up with others likely getting us closer to a 'global optimum'.

I do think pure unilateralism is unlikely because even a totally self-interested state would seek allies to reduce opposition. Do you disagree? I don't think I made any claim that this would automatically tend to a utilitarian optimum. Quite the contrary.

Actually.... thank you. I'm skeptical of geoengineering, but open to learning. I appreciate you taking the time to post this. Nothing like a little light reading over the holidays!

Skepticism is the right outlook on something with such obvious potential downsides.

Is this the silica flakes idea supported by @BillGates to reflect back the harmful rays? Thank you, Dr Keith.

Hum... about everything here is confused. Yes Gates has supported or work. But I don't know what you mean by silica flakes. See if the talk answers your questions.

Loved the talk! You mention the release of sulfur by current plane flights, but "kilograms of sulfur every minute" (40:50) seems like it would dwarf a 1.5Mt project - 2kg*120m time in air*40M flights = 9.6Mt per year into the lower stratosphere. How big an effect is this already?

Some other figures online suggest total sulfur per flight more like 10kg, which would produce 0.5Mt total. Is this already having an effect on the climate we can measure, or does suboptimal location (away from tropics, wrong altitude?) mean that the effects are negligible?