Alvia: You're right: "There is also some confusion, I believe in what we are calling "stratospheric aerosols" over the Arctic. The Pinatubo aerosols were in the Overworld stratosphere, the stratosphere above the altitude of the tropical tropopause (>53,000 ft.) Benford's proposal along with others that seek to have the aerosol descend and be gone before the Arctic winter involves "tropospheric aerosols" or other sunlight scattering materials. The altitude at issue here has never been clearly stated, but I assume it is to be around 40,000-45,000 ft, close to the magic 53,000, but not above it and high enough to guarantee aerosol lifetimes of several months. If you want to use airplanes like the 747, the KC-135, the "extender" or even the B-52, that's about as high as you are going to be able to go."
I originally thought of the 40,000-45,000 ft site, but as you say, this demands some real measurements. That's what early, small field tests with tracer aerosols can discover. It's clear that research might usefully break down into distinguished phases: 1. Lab development. How do aerosols deploy and evolve in stratospheric conditions? How to deploy them? Where? What level? etc Do these in high vacuum chambers such as the JPL 3-story one, which can adjust gas pressure and temperature. Most lab experiments are wall dominated and not useful for real numbers. But nozzle design, local chemistry etc can be done in them. (There's a group at NASA Ames that does this. And others, too--but those I know because I looked into doing this work there.) 2. Local Field Tests The Arctic stratosphere begins in the 8 to 10 km range, easily reached by the KC-10 Extender. This midflight refueler is about to be replaced, so plenty are available and well understood, with experienced pilots. I calculate that a test in the Arctic over roughly 150 mile perimeters would give decent diagnostics of the main parameters -- descent time, spreading rate, temperature changes, chemistry, etc. I think regional, local tests can be done quietly and well for low cost. To truly try to cool a small region of the Arctic, after due diplomacy with the Arctic Council (and only them), could cost well under $ 100 million. 3. Cooling the whole Arctic would be best to hand off to a civilian agency, costing about 1 $ billion/year. NOAA satellites, Arctic Council measurements on their territories, and in situ measurements in the stratosphere and troposphere, would be essential. Sea ice is the best overall diagnostic tracer. This agenda we can organize, but until a sea change in attitude occurs, there's no funding. Calculations of the angular effects, down-reflection etc, as this list has seen this week, are complex and need a full study. Gregory Benford --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
