Jeff Ridley calculated albedo effect, as follows: The effect on global temperatures can be calculated as follows
[quote] 1. The albedo of summer Arctic sea ice is 0.46 2. Clouds are the same albedo as ice and partially obscure the ice reducing to an effective albedo of 0.23 (a figure reached by a number of authors). 3. The summer solar input at the Arctic is about 400 W/m2, thus if all the ice were removed then the balance at the surface would be 0.23 x 400 = 92 W/m2. This is a large local effect - roughly equivalent tot the change in heat from a cloudy day to a clear day. 4. Because of the annual cycle and no sunlight in winter we take a third of this 30 W/m2 on the annual average 5. Summer sea ice covers only 1.6% of the world's surface so the global effect is 30 x 0.016 = 0.48 W/m2 This is not insignificant! 6. A rule of thumb is that 1 W/m2 forcing is equivalent to 1 Kelvin temperature rise. Thus the direct effect of removal of all Arctic sea ice would raise global temperatures by about 0.5 C. The removal of say 20% extra ice in 2007 would thus be expected to have a 0.1 C impact on global temperatures. [end quote] I would use 70% as the albedo flip, between ice/snow (~80%) and water (<10%). But Jeff reduces the albedo change to about a third, at 0.23%, taking into account cloud cover. When we apply aerosols in the stratosphere, they will become less effective due to clouds in the troposphere. Thus to exactly counter the albedo flip where it happens, aerosols would have to reduce insolation by 70%, I think. Any comments? John --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
