http://www.grida.no/climate/ipcc_tar/wg3/176.htm
"In principle, only ~10^5t of such mesh structures are required to achieve the benchmark 1% increase in albedo." http://www.ucalgary.ca/~keith/papers/26.Keith.2000.GeoengineeringHist... "Teller et al (8) note that a scattering system at the L1 point need only deflect light through the small angle required for it to miss the earth, about 0.01 rad as compared to 1 rad for scatterers in near earth orbit or in the stratosphere..." You missed Keith's preceeding comment about positioning such a "system" at L1. He noted that: " The obvious geometry is a fleet of shields in low-earth orbit (NAS92). However, solar shields act as solar sails and would be pushed out of orbit by the sunlight they were designed to block. The problem gets worse as the mass density is decreased in order to reduce launch costs. A series of studies published in 1989–1992 proposed locating the shield(s) just sunward of the L1 Lagrange point between the Earth and sun, where they would be stable with weak active control." That phrase "active control" is the problem. Control implies structure to keep the mass together while force(s) are applied to counter the effects of solar wind and solar pressure. Those forces must be produced by reaction, ie, rockets that throw away mass. Even electric propusion requires some source for the mass being thrown overboard and some additional mass to produce the electricity, perhaps PV cells. Supplying all this mass would require servicing and constant maintenance for as much as 1,000 years after the fossil fuels are gone. Building something this large would make the Space Station look like a flea. Providing this is very expensive with today's technology. Your off-hand comment about costs is silly, as this alternative looks grossly expensive to me. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. 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/globalchange -~----------~----~----~----~------~----~------~--~---
