Hi Ken, One compelling reason for deploying stratospheric aerosols is at high latitudes to save the Arctic sea ice. And I believe this IS an emergency, because if the Arctic sea ice goes, as it threatens to, there is a real possibility that methane discharge from permafrost will escalate irreversibly and ice discharge from Greenland will escalate irreversibly. And then I really believe we've had our chips (i.e. collapse of civilisation will almost inevitably follow).
Now is it possible to weigh the probabilities and risks of using stratospheric aerosols for this (e.g. using Alan Robock's list, but bearing in mind much reduced aerosol quantities for this specific use), against the probabilities and risks of the Arctic sea ice going with disastrous and irreversible consequences? And, if the latter risks outweigh the former, what is the optimum time to apply aerosols, assuming that other geoengineering techniques may not be ready for large scale deployment within years? (In particular, the marine cloud brightening technique is still at "early stage" as John Latham admits.) People, including yourself, keep talking about geoengineering as a last resort, but the hurdles to be overcome are getting higher all the time, especially as the Arctic warms. "A stitch in time saves nine". Less than a billion dollars per year spent on Arctic geoengineering, if started forthwith, might have a good chance to save nine billion lives this century (assuming that we also do what's necessary to avoid other critical problems like ocean acidification). What's the downside of Arctic geoengineering in comparison? Cheers, John ----- Original Message ----- From: Ken Caldeira To: [email protected] Cc: geoengineering Sent: Tuesday, April 21, 2009 12:03 PM Subject: Re: [geo] EGU meeting, April 19-24 [snip] It is my view that there would need to be some mighty compelling reasons to deploy a stratospheric aerosol system, if not only because people who experience bad weather in subseuqent years might be incented to sue (or even attack militarily) parties engaged in aerosol release. So, if we in an emergency situation acid rain, ozone loss, etc would be among the costs taken into account before making a decision, but these costs may not be decisive. I still think Mt Pinatubo is the poster child for stratospheric aerosols approaches: We know it can cool the Earth, we know it can do this quickly, and we know it does not immediately cause a global catastrophe. Were we faced with a real climate emergency, there could be a lot of pressure to exercise the Pinatubo option. I do not see that the abstract by Eliseev et al markedly changes this picture. [snip] --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
