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Hi all, As I said, I would start a new thread on aerosols, due to Hansen's comments here: http://www.columbia.edu/~jeh1/mailings/2009/20091216_TemperatureOfScience.pdf "The different hemispheric records in the mid-twentieth century have never been convincingly explained. The most likely explanation is atmospheric aerosols, fine particles in the air, produced by fossil fuel burning. Aerosol atmospheric lifetime is only several days, so fossil fuel aerosols were confined mainly to the Northern Hemisphere, where most fossil fuels were burned. Aerosols have a cooling effect that still today is estimated to counteract about half of the warming effect of human-made greenhouse gases. For the few decades after World War II, until the oil embargo in the 1970s, fossil fuel use expanded exponentially at more than 4%/year, likely causing the growth of aerosol climate forcing to exceed that of greenhouse gases in the Northern Hemisphere. However, there are no aerosol measurements to confirm that interpretation. If there were adequate understanding of the relation between fossil fuel burning and aerosol properties it would be possible to infer the aerosol properties in the past century. But such understanding requires global measurements of aerosols with sufficient detail to define their properties and their effect on clouds, a task that remains illusive, as described in chapter 4 of Hansen (2009) [1]." Glacier mass loss has been an excellent proxy for global mean temperature and the rate has corresponded to the CO2 climate forcing until the 80's. I would still like a convincing explanation of why the glacier mass ice loss started accelerating in the 80's [2]. Was it cleaner air with less sulphate aerosol pollution? Was it increased black carbon? Was it some kind of positive feedback gaining hold? Or was it combination of factors? And has there been a difference in glacier retreat between northern and southern hemispheres? Cheers, John [1] Hansen(2009): “Storms of My Grandchildren.” Bloomsbury USA, New York. (304 pp.) [2] http://en.wikipedia.org/wiki/File:Glacier_Mass_Balance.png -- 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. |
