Dear John In my piece I didn't use the term SRM, which I try to avoid, and specifically addressed the application of cloud brightening in such a scenario
Best o On Tuesday, 2 April 2013 20:09:16 UTC+1, JohnLatham wrote: > > SRM and droughts in the Sahel, > > Hello Oliver, Jim, Andy, and All, > > Good to read the several interesting results and arguments, > hopefully to be developed further. > > However, I’d like to request rectification of a common > tendency for the terms SRM, and sometimes climate > geoengineering to be regarded as synonymous with > stratospheric sulphur seeding. The latter is without > question the best known SRM technique, and clearly > has a significant likelihood of proving useful, but > other SRM ideas, including Marine Cloud Brightening > (MCB) and Russell Seitz’s microbubble technique also > have promise and should not be disregarded at this stage. > > Bala, Caldeira et al. found that extensive oceanic > cloud seeding via MCB did not significantly reduce > rainfall over land. Jones et al. found that – with > geographically more limited seeding - the occurrence of > rainfall reduction over land via MCB did or did not occur > dependent on the choice of seeding locations. Our own > work on MCB, with larger seeding areas, gave results > similar to those of Bala et al. So it is too sweeping and > also misleading to say that SRM would cause droughts in > the Sahel. > > Although designed to produce global effects MCB, in > principle, could also be used to address much smaller-scale > issues, such as hurricane weakening and coral reef > preservation: and could perhaps prove helpful regarding > the prevention of polar sea-ice loss > > Best Wishes, John. > > > John Latham > Address: P.O. Box 3000,MMM,NCAR,Boulder,CO 80307-3000 > Email: [email protected] <javascript:> or > [email protected]<javascript:> > Tel: (US-Work) 303-497-8182 or (US-Home) 303-444-2429 > or (US-Cell) 303-882-0724 or (UK) 01928-730-002 > http://www.mmm.ucar.edu/people/latham > ________________________________________ > From: [email protected] <javascript:> [ > [email protected] <javascript:>] on behalf of O Morton [ > [email protected] <javascript:>] > Sent: 02 April 2013 14:53 > To: [email protected] <javascript:> > Subject: [geo] SRM and droughts in the Sahel > > Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall > > * Jim M. Haywood< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#auth-1>, > > > * Andy Jones< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#auth-2>, > > > * Nicolas Bellouin< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#auth-3> > > > * & David Stephenson< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#auth-4> > > > > Nature Climate Change > (2013) > doi:10.1038/nclimate1857 > > Received > 23 October 2012 > Accepted > 22 February 2013 > Published online > 31 March 2013 > Article tools > > The Sahelian drought of the 1970s–1990s was one of the largest > humanitarian disasters of the past 50 years, causing up to 250,000 deaths > and creating 10 million refugees1< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref1>. > > It has been attributed to natural variability2< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref2>, > > 3< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref3>, > > 4< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref4>, > > 5< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref5>, > > over-grazing6< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref6> > > and the impact of industrial emissions of sulphur dioxide7< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref7>, > > 8< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref8>. > > Each mechanism can influence the Atlantic sea surface temperature gradient, > which is strongly coupled to Sahelian precipitation2< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref2>, > > 3< > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html#ref3>. > > We suggest that sporadic volcanic eruptions in the Northern Hemisphere also > strongly influence this gradient and cause Sahelian drought. Using > de-trended observations from 1900 to 2010, we show that three of the four > driest Sahelian summers were preceded by substantial Northern Hemisphere > volcanic eruptions. We use a state-of-the-art coupled global > atmosphere–ocean model to simulate both episodic volcanic eruptions and > geoengineering by continuous deliberate injection into the stratosphere. In > either case, large asymmetric stratospheric aerosol loadings concentrated > in the Northern Hemisphere are a harbinger of Sahelian drought whereas > those concentrated in the Southern Hemisphere induce a greening of the > Sahel. Further studies of the detailed regional impacts on the Sahel and > other vulnerable areas are required to inform policymakers in developing > careful consensual global governance before any practical solar radiation > management geoengineering scheme is implemented. > > Full article at > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1857.html > > Blogpost by me at > http://heliophage.wordpress.com/2013/03/31/climate-geoengineering-for-natural-disasters/ > > > Extract: One implication is that climate geoengineering deployed in just > the northern hemisphere looks like a very bad idea. Programmes in just the > north have been considered and studied, in part because of the worries > people have about something suddenly going wrong in the Arctic, something > that needs “fixing” quickly. This research makes such approaches look > dangerous. > More interesting, and more novel, is the implication that geoengineering > might be used to avert a Sahelian drought caused by a volcano. If the > stratospheric sulphates released in a major northern eruption were promptly > countered by a deliberate release of sulphates into the southern > hemisphere, both hemispheres would cool. The ITCZ would stay put, and a > drought might well be averted. For a major drought, that would be a big > win. The drought in the 1980s, which followed on the 1982 eruption of El > Chichon in Mexico, killed about a quarter of a million people and turned > millions more into refugees. > ... > And if the Earth is left to its own devices, such droughts will happen > again. Last century there were two eruptions that cooled the north and were > followed by drought in the Sahel. The north is better endowed with > volcanoes than the south, since the Pacific “ring of fire” is more a > horseshoe of fire, with a gap in the south but a continuous arc in the > north. The odds of at least one eruption in the Pinatubo-to-Krakatoa range > somewhere of the Earth in this century are better than even. The chances of > one happening in the north are obviously lower; but the odds are hardly > long. > If humans had had the technological wherewithal to stop the 1980s Sahel > drought in its tracks, would people have wanted to use it? It seems likely > that there would have been a constituency for it, not least in the Sahel. > And many of the reasons people have for objecting to geoengineering as an > inappropriate “technical fix” to man-made climate change might apply with > rather less force if the technology was being used to forestall a natural > disaster on a continental scale. > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To post to this group, send email to > [email protected]<javascript:>. > > Visit this group at http://groups.google.com/group/geoengineering?hl=en. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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