Hi All Oliver is being too pessimistic. If it seems as if we are overdoing the cooling and emission reductions we rapidly switch off the cooling systems and start releasing some of the sequestered CO2, perhaps even persuading people to burn more coal.
Any control engineer will tell you that all that is needed are low phase lags in the instrumentation system that tells us the temperature error and the control system that applies the correction. If the the loop gain is less than unity when the two phase lags get to 180 degrees the system will be stable at the point we choose. This may look difficult now but so was riding a bicycle along a twisty road before we knew how to do it. Stephen Oliver Wingenter wrote: > Dear Group, > > To me a runaway greenhouse means the negative feedbacks have been > overwhelmed by accelerating positive forcing. In such a case only an > ice age could reverse the runaway effect, a few other checks could > contribute (CLAW hypothesis). If an ice age cannot cool the planet > and stop the positive feedbacks, temperature will increase until we > reach a new steady state. I don't know what that would be. Some have > said that we could end up as the next Venus. > > Sincerley, > > Oliver Wingenter > > On Feb 2, 4:59 am, Govindasamy bala <[email protected]> wrote: > >> Runaway feedback means running its course completely. It is feedback >> specific. >> >> A good example is the presumed water vapor feedback on Venus. >> Apparently, earth and venus started with similar amount of h2o. >> Because Venus started with much higher surface temperature, the evolution of >> temperature and water vapor never intercepted the phase line of vapor and >> liquid. The climate warmed until all the water got evaporated. Basically, >> there was no sink for vapor which precipitation. On earth, this is not going >> to happen because we got the precipitation sink on earth...how lucky we are. >> >> But I guess we do have runaway ice-albedo feedback on earth. we could get >> ice-free planet or snowball earth........ >> >> Cheers. >> Bala >> >> On Mon, Feb 2, 2009 at 5:03 PM, Eugene I. Gordon >> <[email protected]>wrote: >> >> >> -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
