Cloud Brightening

Emergency Climate Protection

By John Latham

Global Cooling is an informal group of collaborating scientists from the US and UK examining Cloud Brightening; an idea for creating a controlled global cooling to balance global warming resulting from burning fossil fuel. This group is organized by Dr John Latham, National Center for Atmospheric Research, Boulder, Colorado, who first published the idea, which involves seeding marine clouds to increase their reflectivity.

We propose to mitigate global warming by increasing the reflectivity of low ocean clouds. A fleet of wind-powered satellite controlled vessels spraying a fine mist of seawater into maritime clouds could increase their reflectivity.

Computer modeling shows that this could reverse the loss of polar sea ice and thereby hold back the heating feedback loop caused now as reflective ice is replaced by dark water.

This could in turn be the key to averting the massive release of methane from permafrost, which potentially threatens to cause an even more dangerous run-away warming phenomenon.

Technical Abstract from a 30 page paper presented at the Royal Society in London, November 2010 html or PDF

Combined LOI & RFP for a 2011 grant application html or 10 page PDF

The likelihood that the major countries of the world will limit their carbon dioxide emissions sufficiently to prevent disastrous consequences before carbon-free energy sources are developed to replace fossil-fuel burning are slender, and it is therefore imperative to devote resources to the examination of possible 'geoengineering' ideas for suppressing further warming, probably for several decades, until clean-energy sources are in full operation.

Latham and colleagues are examining one such idea, which involves making low-level marine clouds, which cover about a third of the ocean surface, more reflective to incoming sunlight, thereby producing a cooling effect adequate to balance global warming. This idea has been published in a number of peer-reviewed articles and has received a positive response internationally when presented at numerous conferences and research institutions.

We now have about 25 scientists and technologists – some world-ranking - from 7 institutions in the US & the UK: [NCAR, PNNL, Silver Lining, U of Washington, U of Edinburgh, U of Leeds, U of Manchester] working on cloud brightening in a voluntary capacity. i.e. they are not paid to do so – we have no funding, except for one PhD student – the others are either retired, or more commonly have managed to incorporate cloud brightening studies into their full-time research positions.

Our geoengineering idea (first advanced by Latham, 1990) involves increasing the reflectivity (albedo) of the Earth to incoming sunlight. Obviously, if a greater fraction of the sunlight arriving at the top of the atmosphere is reflected back into space, the overall result is a cooling of the Earth. Our calculations (Latham, 1990, 2002; Bower et al. 2006, Latham et al.2008, Rasch et al 2009) indicate that adequate cooling could be achieved by increasing the reflectivity of low-level shallow maritime clouds - which cover a large fraction of the oceanic surface - by atomizing sea-water beneath them to produce tiny droplets, a significant fraction of which enter the clouds, act as centers for additional droplet formation, and thus, for well-established physical reasons, cause them to become more reflective. Plans – spearheaded by Stephen Salter (Salter et al, 2008), and – separately, by Armand Neukermans – are well advanced for dealing with the crucial engineering problems of the production and dissemination of these seawater droplets at the rates and on the geographical scales required. Although conventional vessels might be used, we have given most attention to the idea that these particles would be disseminated from unmanned, satellite-controlled, wind-powered vessels designed by Salter and based on an original design by Anton Flettner in the nineteen twenties.

Cloud Brightening has the advantages that: (1) the only raw material required is seawater; (2), if necessary, the system could be switched off and conditions would return to normal within a few days. However, as with all geoengineering ideas, there are a number of important meteorological and safety ramifications which must be fully and satisfactorily examined before operational deployment of such an intervention would be justified. These include assessments, which require major computations using the best available global climate models, of the influence of any possible deployment on rainfall. It may well prove advantageous that our idea does not require full global seeding, because – to a significant degree – we could choose to seed only those clouds which would have minimal adverse impact.

We have no doubt that the ultimate solution to global warming will be to reduce fossil fuel combustion by the requisite amount to halt further temperature rise, we but are also convinced that such a reduction is highly unlikely to occur in the near future. If our idea (or any other reflectivity enhancement or global cooling technique) could successfully be deployed, it would not, of course, affect the atmospheric carbon dioxide levels, whose increase has injurious planetary effects which will need to be addressed, in addition to temperature. However, if it proved feasible, in a controlled way, to produce a cooling to compensate for global warming, we could buy time within which to stave off catastrophic warming and maintain the ice cover at both poles while clean energy sources which could take over from fossil fuel burning are being developed (Latham, 2007). We are very encouraged by the positive reactions to our idea from climate scientists. We regard it as deplorable that resources have so far not been provided to enable any such ideas to be adequately assessed.

Our Cloud Brightening idea has been favorably received by the scientific community and we have published eight papers on it. We are currently actively seeking funding on a non-profit basis under the auspices of Global Cooling. For more information please see the info below and email John Latham.

PDF summary (download)

Global Cooling
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Eight papers (in reverse chronological order) on Cloud Brightening:

P.J.Rasch, J. Latham & C.C.Chen, 2010. Geo-engineering by Cloud Seeding: influence on sea-ice & Climate System. Environ. Res. Lett. 4 045112 (8pp) (doi:10.1088/1748-9326/4/4/045112).

S. Salter, G. Sortino and J. Latham, 2008. Sea-going Hardware for the Cloud Albedo Method of Reversing Global Warming Phil.Trans.Roy. Soc. A, 366, 2989-4006, (doi:10.1098/rsta.2008.0136).

J. Latham, P.J. Rasch, C.C.Chen, L. Kettles, A. Gadian, A. Gettelman, H. Morrison, S. Salter., 2008. Global Temperature Stabilization via Controlled Albedo Enhancement of Low-level Maritime Clouds. Phil. Trans. Roy. Soc. A, 366, 3969-3987, (doi:10.1098/rsta.2008.0137).

J. Latham, 2007. Cooling may be possible, but we need safety data. Nature, 447, 908.

K.Bower, T.W.Choularton, J.Latham, J.Sahraei and S.Salter., 2006. Computational Assessment of a Proposed Technique for Global Warming Mitigation Via Albedo-Enhancement of Marine Stratocumulus Clouds. Atmos. Res. 82, 328-336.

Latham, J., 2002, Amelioration of Global Warming by Controlled Enhancement of the Albedo and Longevity of Low-Level Maritime Clouds. Atmos. Sci. Letters. (doi:10.1006/Asle.2002.0048).

J Latham and M H Smith: 1990 Effect on global warming of wind-dependent aerosol generation at the ocean surface. Nature, 347, No. 6291, 372-373.

Latham, J., 1990: Control of global warming? Nature 347. 339-340.

Global Cooling is a fiscally sponsored non-profit project of Planetwork NGO, Inc. a CA 501(c)3.
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