Postal Address: P.O. Box 3000, Boulder, CO, 80307-3000
Shipping Address: 3090 Center Green Drive, Boulder, CO, 80301
John Lathamís principal current research interests are in the fields of cloud physics, atmospheric electricity and global climate. More specifically, he is working on (1) the glaciation of convective clouds, (2) the electrification of thunderstorms, (3) the relationships between lightning frequency and other thundercloud parameters, and (4) a possible global warming mitigation technique (please see "Research on Global Warming..." section, below) involving controlled enhancement of the reflectivity of maritime stratocumulus clouds. His main collaborators in the above-mentioned research are scientists from UK universities and NASA. His publications on these and related topics can be accessed via the link on this homepage. John Latham is also a published writer (poetry, novel, stories, plays) a brief summary of which activity can be accessed via the link to his literary vita, on this homepage.
John Latham’s principal current research interests are in the fields of cloud physics, atmospheric electricity and global climate. More specifically, he is working on (1) the glaciation of convective clouds, (2) the electrification of thunderstorms, (3) the relationships between lightning frequency and other thundercloud parameters, and (4) a possible global warming mitigation technique (please see "Research on Geo-engineering (Cloud Brightening)” below) involving controlled enhancement of the reflectivity of maritime stratocumulus clouds. His main collaborators in the above-mentioned research are scientists from US and UK universities and research institutions. His publications on these and related topics can be accessed via the link on this homepage. John Latham is also a published writer (poetry, novel, stories, plays) a brief summary of which activity can be accessed via the link to his literary vita, on this homepage.
In the following paragraphs we provide a non-technical account of our Cloud Brightening geoengineering idea. We outline the current status of the work, the personnel involved, major achievements, papers published, problems yet to be resolved etc. For readers requiring more detailed information we provide access to our published papers herein.
Rationale for our Geoengineering Effort: Summary
The escalating global warming resulting from the burning of fossil fuels seems likely to have an ever-increasing number of adverse, irreversible and possibly catastrophic consequences. The establishment of some technique for holding the Earth's temperature constant until a clean form of energy is developed to take over from oil, gas and coal is therefore an urgent requirement. We are examining the possibility of seeding maritime clouds with large quantities of small seawater particles to make them reflect more sunlight, thus producing a cooling, which computations employing world-class global climate models suggest could balance predicted global warming for perhaps 50 years, if technological and other issues are resolved. The computations also indicate that the sea-ice cover at both poles could be maintained at current levels, thereby preventing the runaway global heating situations that could result from (1) transforming highly reflective snow and ice, which bounces most sunlight that lands on it back into space, to highly absorptive seawater: (2) the release of large quantities of methane resulting from the melting of the permafrost. We need to engage in further studies of all relevant scientific and technological aspects of this idea - and also identify and assess all likely ramifications of its possible global deployment - in order to determine unequivocally whether or not it can play the crucially important role of suppressing global warming. Currently, no funding is available for the pursuance of these necessary studies.
The Cloud Brightening Geoengineering technique.
Since it appears increasingly unlikely that the major countries of the world will reduce their carbon dioxide emissions rapidly enough to prevent disastrous consequences, it has become imperative to examine 'geo-engineering' ideas for suppressing warming for several decades, until clean-energy sources can be identified and deployed on a global scale. Colleagues and I are examining one such possible technique, described below.
The basic idea (proposed by Latham, Nature, 1990) is to increase the reflectivity of the Earth to incoming sunlight, thus producing a cooling. Our calculations (Latham, 1990, 2002; Bower et al. 2006, Latham et al. 2008, Rasch et al. 2009), indicate that cooling sufficient to hold the Earth's temperature constant for perhaps 50 years could be achieved by increasing the reflectivity of low-level shallow maritime stratocumulus clouds - which cover a huge area (between about a quarter and a third) of the oceanic surface - by seeding them with sea-water droplets, (typically about 1 micrometer in size) sprayed into the atmosphere below the clouds. These particles act, on entry to the clouds, as centers for additional droplet formation, thus increasing the droplet number concentration, thereby causing the clouds - for well-established physical reasons - to become more reflective. These clouds are naturally (i.e. without seeding) very important climatologically, as they bounce back into space about half the sunlight that lands on them (The Earth would be much warmer if these clouds did not exist). Our calculations (supported by those of other scientists) indicate that if we could increase the average cloud reflectivity from about 50% to 60% the associated global cooling would be adequate to balance the warming resulting from a doubling of the atmospheric carbon dioxide (CO2) concentration, which will probably not occur for a few decades. Ship-tracks (lines or streaks of cloud brightening - observed from satellites - which follow the trajectories of ships passing underneath the clouds, and are caused by particles in the ships' exhausts rising into the clouds and creating additional cloud droplets - provide direct confirmation of the occurrence of cloud whitening, but to be useful climatologically - i.e. to produce a significant global cooling - we need to seed clouds on a much larger scale.
One set of plans for dealing with the crucial engineering problems of the production and dissemination of seawater droplets at the rates and on the geographical scales required are described in Salter, Latham & Sortino (2008), full reference below. It is proposed therein that these particles will be disseminated from unmanned, satellite-controlled, wind-powered vessels, an artist's impression of which is shown in Figure 1 below. The Discovery Channel manufactured a slightly smaller version of these "Flettner Vessels" for a 1-hour documentary film it produced on our cloud brightening scheme. It worked perfectly. It is not yet clear whether Flettner vessels would be utilised if our cloud brightening scheme was ever to be deployed, or whether more conventional vessels would be chosen. The former have significant ecological advantages over the latter. Professor Salter and colleagues at the University of Edinburgh are working on a spray production system, based on silicon micro-fabrication technology. Alternative spray production techniques based on electrohydrodynamic liquid breakdown are being investigated by Dr Armand Neukermans and his team of scientists & engineers, in California.
This cloud brightening global cooling technique has the advantages that: (1) if Flettner vessels are used, the only raw materials required are wind and seawater; (2) the amount of global cooling could be adjusted by switching on or off, by remote control, sea-water droplet generators mounted on the vessels employed; (3) if necessary, the entire system could be immediately switched off, with conditions returning to normal within a few days; (4) since not all suitable clouds need to be seeded, there exists, in principle, flexibility to choose seeding locations so as to optimise beneficial effects and subdue or eliminate adverse ones.
Conclusions from our Work to Date
Although design work on the major technological aspects of our work has progressed well despite the absence of funding, significant support will be required in order to produce and test prototypes, particularly of the spray system. Accordingly, the aspect of our work that is most advanced at the moment is global climate modeling of our cloud brightening scheme. We have been fortunate in having access to two of the World's best climate models, emanating from the Hadley Center, Meteorological Office, UK, and the National Center for Atmospheric Research, US. Both of these models have been used, separately, to assess our idea, with Dr Phil Rasch directing our work in the US, and Dr Alan Gadian the work in the UK. To date, two papers (cited below) have been published on these GCM studies, and can be accessed herein.
The results so far have been encouraging. The computations predict - subject to caveats mentioned below - that our cloud brightening scheme could hold the Earth's average surface temperature and polar sea-ice coverage (both poles) roughly constant at least up to the point where the atmospheric CO2 concentration is doubled, which might be thirty or fifty years from now. i.e. the scheme could potentially provide several decades of remission, within which to develop and deploy a new primary global energy source to replace the burning of fossil fuels.
Figure two presents specimen results on the crucial sea-ice maintenance issue. It shows that CO2-doubling (without seeding) in the Northern and Southern Hemisphere summers reduces the sea-ice coverage at both poles considerably from current values, but that by seeding about 60% or 70% of the suitable oceanic cloud-cover, the sea-ice coverage is restored. In fact, there is over-compensation in the Southern Hemisphere.
The main caveats alluded to earlier are: (1) that all important technological issues are satisfactorily resolved: (2) that the reflectivity increase of the oceanic clouds is roughly as assumed in our GCM work. There exists some limited supportive evidence from satellite studies, but more is required, and we need to acquire a much deeper and more comprehensive understanding of the characteristics and behavior of marine stratocumulus clouds, which are in reality significantly more complex than our GCM modeling assumes. We have recently initiated the required cloud modelling : (3) that there are no unacceptable ramifications of the deployment of the scheme that cannot be corrected: (4) the GCM computations are supported by the results of an authoritative, comprehensive limited-area field experiment. If rigorous testing of these four issues (and others) does not provide results which are compatible with the assumptions implicit in our modeling, there would be no justification for deploying this geoengineering idea. These issues are currently under examination.
Reactions to our Cloud Brightening Geoengineering Idea.
We have published seven papers (listed below) in a number of peer-reviewed scientific journals. Two comprehensive ones appeared, in 2008, in a special geo-engineering issue of the venerable and prestigious Philosophical Transactions of the Royal Society. This issue constitutes the most up-to-date, comprehensive and authoritative assessment of such climate mitigation projects. Articles about our work have appeared in many popular and scientific magazines, including Scientific American, The New York Times and Nature, both in the US and abroad. There have been a number of interviews of members of our team on TV and radio, in several countries. It has received a strongly positive response internationally (via conferences, workshops, seminars etc). It has been the subject of two TV documentaries (BBC and Discovery Channel). The UK Royal Society conducted a thorough survey of all geo-engineering schemes, and ours was one of only two global cooling techniques recommended for support. A similar assessment by the Copenhagen Consensus Center concluded that our cloud brightening scheme was the most promising one. In essentially all cases, the reactions to our idea have been favourable. Presentations describing our technique have been made to Congress and to a UK parliamentary committee.
The following collaborators are actively involved in our Cloud Brightening work.
PNNL, Richland, WA .. Dr Phil Rasch, Dr Hailong Wang.
NCAR, Boulder, CO . Dr Jack Chen, Dr John Latham.
NOAA, Boulder, CO . Dr Graham Feingold.
U.Washington, Seattle, WA . Dr Rob Wood, Dr Cecelia Bitz
Silver Lining, CA. Ms Kelly Wanser, Dr Armand Neukermans, Dr Gary Cooper, Mr David Donald, Mr David Johnston, Dr Jack Foster, Dr Lee Galbraith, Dr Bob Ormond, Mr John Rush, Dr Qin Wang.
Purdue University , Dr Dan Hirleman
Manchester University, UK . Dr Keith Bower, Dr Tom Choularton, Dr Hugh Coe, Dr John Latham, Dr Brian Launder, Dr Hector Iacovides & Dr Tim Craft
Leeds University, UK. Dr Alan Gadian, Dr Alan Blyth, Mr Ben Parkes, Ms Laura Stevens
Edinburgh University, UK. Dr Stephen Salter, Dr Tom Stevenson, Dr Camelia Dunare.
Sevilla University , Spain Dr Alfonso Ganan-Calvo.
Karlsruhe University, Germany , Dr Thomas Leisner
Publications emanating from our Cloud Brightening Work
We have published eight papers on our work to date. They are:
1. Latham, J., 1990: Control of global warming? Nature 347. 339-340. (PDF)
2. 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. (PDF)
3. Latham, J., 2002, Amelioration of Global Warming by Controlled Enhancement of the Albedo and Longevity of Low-Level Maritime Clouds. Atmos. Sci. doi:10.1006/Asle.2002.0048. (PDF)
4. 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. (PDF)
5. J. Latham, 2007. Cooling may be possible, but we need safety data. Nature, 447, 908.
6. 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. (PDF)
7. 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. (PDF)
8. 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 (PDF)