[geo] Re: Geoengineering for real - starting asap

[John Nissen]

Dear Alan, The reason I am concerned about statospheric aerosol effectiveness, is because of some figures from your paper [1].  Quote: The global average reduction in downward shortwave radiation at the surface for the Arctic 3 Mt/yr is only about 0.2 W m-2, while for the Tropical 5 Mt/yr run it is 1.8 W m-2 (Figure 2). When Jeff Ridley did the calculation of the forcing effect of albedo change, with just with disappearance of sea ice, he came up with 0.48 W/m-2, see [2].  But he was taking an effective albedo change of 0.23 which seems very small to me.  And this is without taking into account the added albedo change when snow on land melts - over a massive area in Siberia and Canada.  I believe we have had this additional forcing this year.  Of course the local forcing is going to be much greater than the global forcing - so where it occurs it is around 30 W/m-2.  That is an enormous forcing to counter with a reflective aerosol haze. Thus I am not confident in your assertion that geoengineering could save the sea ice, when we can see how much positive feedback has built up already.  To quote you again: Because of the observed rapid decrease in summer Arctic sea ice [Kerr, 2007], even larger than climate model predictions [Vinnikov et al., 1999; IPCC, 2007; Stroeve et al., 2007], one of the goals of proposed geoengineering is to prevent the disappearance of Arctic sea ice in the summer and the resultant large consequences for the entire ecosystem, including endangered or precarious indigenous species, such as polar bears and walruses. Figure 9 shows that both the Arctic 3 Mt/yr and Tropical 5 Mt/yr cases produce much more sea ice in September, the time of minimum sea ice extent. This is shown in the time series of September Arctic sea ice in Figure 10, which also shows rapid ice melting as soon as geoengineering stops. This is why I am asking you whether you are still confident that SRM could be used to cool the Arctic. Best regards, John [1] Regional Climate Responses to Geoengineering with Tropical and Arctic SO2 Injections. http://www.agu.org/pubs/crossref/2008/2008JD010050.shtml [2] http://www.mail-archive.com/geoengineering@googlegroups.com/msg00658.html --- John Nissen wrote: Hi Ken, Alan, The predictions of sea ice lasting for decades are about to be proved wrong.  The sea ice extent declined by 208000 square kms yesterday.  36 days like this and it will all be gone.  We are heading for what I have been absolutely dreading: a near ice free Arctic in September.   Thus by my "simple argument" for geoengineering [1], that you must be quite tired of reading, we have to apply SRM.  (In the press release, we've ignored the sea level rise.) The rapidity of retreat has taken many by surprise because of neglecting the terrestrial albedo flip.  Siberian snow cover is record low, and temperatures are record high.  Can stratospheric aerosols reflect sufficient sunlight to offset the albedo flip, BOTH of ice on sea AND of snow on land, as they melt away in summer?  Put another way, is there a chance to cool the Arctic and save the sea ice?  Or have we left it too late?  In which case, what is there to do? Best regards, John [1] http://www.mail-archive.com/geoengineering@googlegroups.com/msg03004.html ----- Draft press release: SEA ICE LOSS STUNS SCIENTISTS For Press Release The Arctic sea ice acts as a giant mirror to reflect sunlight back into space and cool the Earth. It has been retreating far faster than the Intergovernmental Panel on Climate Change predicted only three years ago. But, after the record retreat in September 2007, many scientists revised there predictions for the date of a seasonally ice free Arctic Ocean from beyond the end of century to beyond 2030. Only a few scientists predicted this event for the coming decade, and they were ridiculed. However seasonal ice is currently at the lowest level ever for this time of year and is retreating faster than ever before. On 24th June, the sea ice declined by a staggering 208,000 km² which is 112,000 km² above normal (1979-2008 mean) for this time of year.   If the retreat continues at this pace, there will be little sea ice left at the end of summer and we can expect a seasonally ice free ocean in future years. Loss of sea ice causes Arctic warming to accelerate, resulting in increased discharge of methane from vast quantities trapped in permafrost.  The methane, as a potent greenhouse gas, could exacerbate global warming to provoke further discharge, triggering long term and very severe disruption to the Earth's climate. We may now be at the brink of a climate emergency. We suggest that the current situation should be treated as a warning for us all. The world community must rethink its attitude to fighting global warming by cutting greenhouse gas emissions sharply. However, even if emissions could be cut to zero, the existing CO2 in the atmosphere would continue to warm the planet for many decades.  Geoengineering now appears the only means to cool the Arctic quickly enough.  A geoengineering project of the intensity of the Manhattan Project is urgently needed to guard against a global catastrophe. Yours sincerely, John Nissen John Gorman Albert Kallio Sam Carana Professor Stephen Salter, Emeritus Professor of Engineering, Edinburgh University Professor Peter Wadhams, Head of the Polar Ocean Physics Group, Cambridge University John Nissen, College House, Chiswick Mall London W4 2PR Tel: 020 8742 3170 -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to geoengineer...@googlegroups.com. To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.