Hi Ken and others interested in albedo engineering, Below is a draft letter I am writing in response to Professor Jim Hansen's latest missive: http://www.columbia.edu/~jeh1/mailings/20081121_Obama.pdf I would welcome comments, and suggestions to flesh out the existing references or add more pertinent ones.
Cheers from Chiswick, John (alias Professor Chiswick - thanks for that promotion, Eugene!) --- Dear Professor Hansen, May I suggest that the situation is even more dire than you suggest, and come to an additional conclusion? In your opening summary you say: Paleoclimate data show that climate sensitivity is ~3°C for doubled CO2, including only fast feedback processes. These "fast feedbacks" include the albedo effect of Arctic sea ice. But the paleodata do not show the Arctic sea ice ever completely disappearing in summer. In fact the Arctic sea ice may have acted as a thermostatic control, preventing interglacial warming exceeding certain limits [1] and thus preventing its own disappearance. However we find ourselves today in a completely unprecedented situation. We have the possibility of summer disappearance within a few years - by 2012 or 2013 according to some experts [2] - thus breaking our own planetary thermostat. This will lead to significant feedback to global warming - in the range 0.4 to 1.6 Watts per square metre [3] - thus suggesting that climate sensitivity is underestimated. But it leads to much greater local warming - more than sufficient to cause massive methane release for frozen structures such as permafrost [4] - more than sufficient to destabilise the Greenland ice sheet and result in a metre or more of sea level rise this century [5]. What is more, the limits of interglacial warming may have protected vital carbon sinks, both terrestrial and oceanic. Thus the loss of Arctic sea ice could result in less than the current 50% of anthropogenic CO2 being absorbed, and again the climate sensitivity is adversely affected. The timescale for saving the Arctic sea ice is far shorter than the timescale for emissions reduction. Even removal of CO2 from the atmosphere by geoengineering could not conceivably be done quickly enough. Thus it seems that the only possibility to save the Arctic sea ice is through albedo engineering. However there are two methods which are feasible to quickly cool the Arctic region - one using stratospheric aerosols [6] and one using marine cloud brightening [7]. These could be used together, to increase the chance of success and allow some fine-tuning of the process, e.g. to minimise unwanted side-effects. Furthermore these methods could scaled up to halt warming globally, and protect the carbon sinks. No serious scientist is suggesting that geoengineering should be used exclusively, or as an excuse to avoid drastic emission cuts. Without such cuts, CO2 will cause ocean acidification. But the magnitude of the danger that we are in militates even more urgent cuts, and a more urgent move to low carbon economies around the world. So I absolutely support your efforts to have CO2 levels reduced to 350ppm or less. But albedo engineering is needed quickly. So my added conclusion is as follows. Barack Obama should be persuaded to set up a project to save the Arctic sea ice, with the focus, determination and urgency of the Manhattan project in WW2. This is the moral imperative. Failure is not an option. Yours, John Nissen [1] Highest temperature of interglacials little different from today's global mean. [2] A group of scientists are arguing that the summer sea ice is likely to be gone in 2012 or 2013. [3] 0.4 is estimate by Jeff Ridley of the Hadley centre, and 1.6 is my own - based on different assumptions. [4] David Lawrence's work, for example. [5] Hansen's own warning. [6] Caldeira et al [7] Salter, Latham et al ---- ----- Original Message ----- From: James Hansen To: [EMAIL PROTECTED] Sent: Friday, November 21, 2008 11:35 PM Subject: Tell Barack Obama the Truth -- The Whole Truth To be removed from Jim Hansen's e-mail distribution, reply with REMOVE as subject. A draft write-up, Tell Barack Obama the Truth -- The Whole Truth, is at http://www.columbia.edu/~jeh1/mailings/20081121_Obama.pdf Criticisms are welcomed -- it was written pretty quickly as I am leaving this weekend for a long trip. Jim --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
