Stephen makes a good point that leads to a more general one. If there are precipitation reductions associated with sunlight blocking schemes, consideration should also be given to mitigating these, analogous to the medications given to patients with Type II diabetes to combat the side effects of the primary drug.
This is an oversimplification, but the way summer monsoons work is that in the summer the land gets warmer than the ocean faster, creating a low pressure area and this causes on shore flow as air moves from high to low presssure. For some reason, Laki caused this to be muted. There were no aerosols from Laki over India and it has been suggested there was a teleconnected response (see the paper Stephen attached) although in paleo climate the authors say the effects were direct, but don't give specifics. In the case of Pinatubo, both the land and sea were cooled by the aerosol and the land simply didn't heat up fast enough to generate the on shore flow. If the Arctic only aerosol geoengineering does cause a reduction in the ISM (Indian Summer Monsoon as there are other monsoons that affect India, but this is the most important one), use of the cloud whitening to restore at least some of the temperature differential should be considered. Likewise, in a global aerosol scheme, with a global aerosol spread similar to that of Pinatubo, the cloud whitening could also be used to create a temperature differential, but at some point it becomes a race to the bottom, with the land temperature simply too cool to initiate the low pressure area. In this case, reducing the depth of the aerosol layer over the land may be the most effective way to restore the dynamics. I previously suggested using ammonia released from either planes or balloons to react with the sulfate aerosol and drop them out as ammonium sulfate. This idea as well as Stephen's could be applied to other locations such as the Amazon, Eastern China and Africa where models indicate unacceptable reductions in precipitation are a result of either aerosol geoengineering or global warming. Of course, the ammonia wouldn't be of any value in a global warming/no aerosol scenario. I said in one the earliest papers I wrote on geoengineering that eventually we were going to have to learn how to manipulate the climate to our advantage. That includes both gross scale and fine tuning. In a related issue, last year I posted a link from a group in the UK that was carrying out some 130 different models of aerosol geoengineering. It was a volunteer effort among universities. If they have done even a fraction of the modeling, this work should be taken into account in designing new studies such as Rutgers is proposing. Anyone have an update? You may recall also that we spent some time last year discussing the significance of the "little brown blotches" in absolute terms and now Ken also raises the issue of their resolution. http://en.wikipedia.org/wiki/Monsoon Monsoons are caused by the larger amplitude of the seasonal cycle of land temperature compared to that of nearby oceans. This differential warming happens because heat in the ocean is mixed vertically through a "mixed layer" that may be fifty meters deep, through the action of wind and buoyancy-generated turbulence, whereas the land surface conducts heat slowly, with the seasonal signal penetrating perhaps a meter or so. Additionally, the specific heat capacity of liquid water is significantly higher than that of most materials that make up land. Together, these factors mean that the heat capacity of the layer participating in the seasonal cycle is much larger over the oceans than over land, with the consequence that the air over the land warms faster and reaches a higher temperature than the air over the ocean.[11] Heating of the air over the land reduces the air's density, creating an area of low pressure. This produces a wind blowing toward the land, bringing moist near-surface air from over the ocean. Rainfall is caused by the moist ocean air being lifted upwards by mountains, surface heating, convergence at the surface, divergence aloft, or from storm-produced outflows at the surface. However the lifting occurs, the air cools due to expansion, which in turn produces condensation. In winter, the land cools off quickly, but the ocean retains heat longer. The cold air over the land creates a high pressure area which produces a breeze from land to ocean.[11] Monsoons are similar to sea and land breezes, a term usually referring to the localized, diurnal (daily) cycle of circulation near coastlines, but they are much larger in scale, stronger and seasonal.[12] ----- Original Message ----- From: "Stephen Salter" <[email protected]> To: <[email protected]> Cc: <[email protected]>; "Andrew Lockley" <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Sent: Saturday, May 09, 2009 6:43 AM Subject: [geo] Re: Balancing the pros and cons of geoengineering > Hi All > > The attached paper by Zickfeld et al shows, in figure 2, what might > happen to the Indian Monsoon if we do nothing. Cooling the sea relative > to the land should move things in the opposite direction. > > Stephen > > Emeritus Professor of Engineering Design > School of Engineering and Electronics > University of Edinburgh > Mayfield Road > Edinburgh EH9 3JL > Scotland > tel +44 131 650 5704 > fax +44 131 650 5702 > Mobile 07795 203 195 > [email protected] > http://www.see.ed.ac.uk/~shs > > > > Alan Robock wrote: >> Dear Ken, >> >> I agree. We need several models to do the same experiment so we can see >> how robust the ModelE results are. That is why we have proposed to the >> IPCC modeling groups to all do the same experiments so we can compare >> results. Nevertheless, observations after large volcanic eruptions, >> including 1783 Laki and 1991 Pinatubo, show exactly the same precip >> reductions as our calculations. >> >> Even if precip in the summer monsoon region goes down, how important is >> it for food production? It will be countered by increased CO2 and >> increased diffuse solar radiation, both of which should make plants grow >> more. We need people studying impacts of climate change on agriculture >> to take our scenarios and analyze them. >> >> Alan >> >> Alan Robock, Professor II >> Director, Meteorology Undergraduate Program >> Associate Director, Center for Environmental Prediction >> Department of Environmental Sciences Phone: +1-732-932-9800 x6222 >> Rutgers University Fax: +1-732-932-8644 >> 14 College Farm Road E-mail: [email protected] >> New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock >> >> >> >> Ken Caldeira wrote: >> >>> A few questions re claims about monsoons: >>> >>> 1. How well is the monsoon represented in the model's base state? Is >>> this a model whose predictions about the monsoon are to be trusted? >>> >>> 2. Since the believability of climate model results for any small >>> region based on one model simulation is low, for some reasonably >>> defined global metrics (e.g., rms error in temperature and precip, >>> averaged over land surface, cf. Caldeira and Wood 2008) is the amount >>> of mean climate change reduced by reasonable aerosol forcing? (I >>> conjecture yes.) >>> >>> Alan is interpreting as significant his little brown blotches in the >>> right side of Fig 7 in a model with 4 x 5 degree resolution (see >>> attachment). >>> >>> How does the GISS ModelE do in the monsoon region? If you look at Fig >>> 9 of Jiandong et al (attached), at least in cloud radiative forcing, >>> GISS ModelE is one of the worst IPCC AR4 models in the monsoon region. >>> >>> So, while Alan may ultimately be proven right, it is a little >>> premature to be implying that we know based on Alan's simulations how >>> these aerosol schemes will affect the Indian monsoon. >>> >>> If you look at Caldeira and Wood (2008), we find that idealized Arctic >>> solar reduction plus CO2, on average precipitation is increased >>> relative to the 1xCO2 world. >>> >>> >>> ___________________________________________________ >>> Ken Caldeira >>> >>> Carnegie Institution Dept of Global Ecology >>> 260 Panama Street, Stanford, CA 94305 USA >>> >>> [email protected] <mailto:[email protected]>; [email protected] >>> <mailto:[email protected]> >>> http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab >>> +1 650 704 7212; fax: +1 650 462 5968 >>> >>> >>> >>> >> >> > >> >> > > > -- > > > > > 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. 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