Alan has made a valuable point, but I think misses another. Geoengineering would sensibly be used within a three-pronged program; and, if you accept the hypothesis that CO2 emissions are the only significant causal factor in global warming (which we are not seeing lately), it would be necessary to ensure the efficacy of the other two elements over the short (well less than 1000 years) time period.
Prong 1. Geoengineering reduces the global temperature. This we need to prevent catastrophic (or devastating) climate change. How long this must go on is a function of the speed and efficacy of the other two companion actions. Prong 2. Reduce or eliminate anthropomorphic carbon emissions. The rate of emissions reduction would sensibly be done in conjunction with the speed and efficacy of prong 3. Prong 3. Accelerate ambient (air) CO2 capture. Some research suggests this might be cost-effective at capture levels equal to existing emission rates and perhaps at greater than existing emission rates. To the degree this is available, the importance of Prong 2 is diminished. Notably, geoengineering also has the side benefit of providing breathing space to ensure we have climate science correct - something the IPCC admits is not particularly well sorted out in many ways, and which many scientists think is not sufficient to be the basis of policy formation where that policy would implicate significant economic dislocation. There really isn't more to this issue that that. There is no credible basis for thinking we would have to use geoengineering for 1000 years and probably not even 100 years. I'd guess we won't need it at all (note the word "guess" and the word "I"), but if we do, I suggest air capture is going to explode as a technology and limit the need for anthropogenic global cooling to less than 20 years. As I'm not going to be alive much more than about 20 years, I will accept wagers on this payable to my children. d. On Tue, Jan 27, 2009 at 11:41 AM, Alan Robock <[email protected]>wrote: > > Dear Gene and all, > > Actually what this paper says is the solar radiation management will > have to be maintained for 1000 years to deal with global warming. > Because the effects of CO2 pollution are irreversible, what this paper > means is the we have to do mitigation now. If we wait 20 years, > geoengineering will not buy us time, as the climate will not return to > pre-emission levels for 1000 years. > > Carbon sequestration from the atmosphere, on the other hand, if it could > be done on a large enough scale, and without side effects, would help > solve the problem, because 40% of the additional CO2 will stay in the > atmosphere forever, as nature will not remove it. > > Alan > > Alan Robock, Professor II > Director, Meteorology Undergraduate Program > Associate Director, Center for Environmental Prediction > Department of Environmental Sciences Phone: +1-732-932-9800 x6222 > Rutgers University Fax: +1-732-932-8644 > 14 College Farm Road E-mail: [email protected] > New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock > > > On Tue, 27 Jan 2009, Eugene I. Gordon wrote: > > > Please note: > > > > http://www.noaanews.noaa.gov/stories2009/20090126_climate.html > > > > It is a blockbuster. How can they ignore geoengineering now? > > > > > > -gene > > > > > > > > > > > > > > > > > > > -- David W. Schnare Center for Environmental Stewardship --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
