(our series concludes with part four presenting the remainder of the important presentation by Dr. Edward Teller and his associates. For the complete series, click Dr. Edward Teller link on left in Blanket Effect)
ACTIVE CLIMATE STABILIZATION:
Practical Physics-Based Approaches to Prevention of Climate Change
Edward Teller, Roderick Hyde, Lowell Wood
Prepared for invited presentation at the
National Academy of Engineering Symposium Complements to Kyoto:
Technologies for Controlling CO2 Emissions,
National Academy of Sciences, 2101 Constitution Avenue NW,
Washington DC 20007,
23-24 April 2002
As already noted, metals are greatly superior to dielectrics with respect to the specific efficiency with which they scatter radiation, and the several novel particular means which we’ve considered for the use of metals in management of radiative forcing indeed reflect a 10-100-fold mass savings, relative to
The geometries of metallic scatterers, as might be expected, center on metal dipoles and metallic screens, with dimensions selected to be comparable to the reduced wavelengths of the portion of the solar spectrum desired to be scattered.
The physics of metallic scatterers – which, to be sure, also include small, thin metallic-walled superpressure balloons – suggest that they could most effectively scatter back into space the UV portions of solar insolation, just as do dielectric scatterers.
These more highly engineered scatterers have significantly higher specific costs-to-emplace in the stratosphere than do dielectric aerosols, but their far lower masses result in estimated annual costs to address the reference year-2100 problem which may be as much as five times less than approaches of comparable power based on dielectrics: of the order of $0.2 B/year.
Since they also would diminish the intensity of a portion of the solar spectrum which is net-damaging to both plants and animals, their ‘side-effects’ are comparably beneficial to those of dielectric aerosol Rayleigh scatterers; again, the net economic cost of deploying such a climate stabilization system would be substantially negative.
Finally, resonant scatterers of sunlight offer huge gains in mass efficiency – although much of this gain seems likely to be lost in ‘packaging’ these materials so that they’re at once harmless and unharmed in the photoreactive stratosphere.
Net, these novel materials appear to offer mass budgets a few-fold lower than the most interesting metallic scatterers but have operating costs comparable to dielectrics for the resulting radiative forcing management system.
Once again, this novel type of climate stabilization probably would be aimed at attenuating the near-UV solar spectrum, and thus would have economic costs were would be net-negative.
Most all of these atmospherically-deployed scatterers remain ‘locked’ into the air mass-parcels into which they are initially deployed and thus eventually descend from the stratosphere, mostly as a result of vertical transport in the polar vortices at high latitudes.
Once out of the stratosphere, they ‘rain out’ along with other tropospheric particulate material.
The quantities so deposited are tiny compared to natural particulate depositions, e.g., wind-lofted dust and volcanic aerosol.
The radiative forcing ‘magic’ results from the mid-stratospheric deployment of these optimally-formed scatterers.
Virtually no natural particulate – with the exception of a small fraction of explosive volcanic ejecta – ever ascends so high, and thus is atmosphere-resident for so very long or ‘works’ so hard in a radiative transport sense; tropospheric particulates usually ‘wash out’ within time-frames of a few days to a couple of weeks.
Even volcanic aerosol particulate typically is far too large to be mass-optimal, and also is loaded with chemical impurities which unfavorably impact stratospheric ozone levels; it’s of interest in the present discussion only as an undoubted proof-of-concept of the several different types of engineered-scatterer systems which we propose.
Finally, deployment of one or more metallic scattering screens so diaphanous as to be literally invisible to the human eye just inside of the interior Lagrange point of the Earth-Sun system and on the Earth-Sun axis represents the absolute optimum of all means known to us for insuring long-term climate stability, and is rather novel.
Barely 3,000 tonnes of optimally-implemented metallic screen suffices to stabilize climate against worst-case greenhouse warming through preferential scattering of near-IR solar radiation so that it just barely misses the Earth, and the same-sized screen in a slightly off-axis position could be used to prevent future Ice Ages, as well, by scattering ‘near-miss’ solar radiation back onto the Earth.
Exactly how to execute the deployment of such a long-term capital asset of the human race at the present time isn’t clear, however, and therefore its cost is indeterminate.
The foregoing considered, then, if you’re inclined to subscribe to the Rio Framework Convention’s directive that mitigation of global warming should be effected in the “lowest possible cost” manner – whether or not you believe that the Earth is indeed warming significantly above-and beyond natural rates, and whether or not you believe that human activities are largely responsible for such warming, and whether or not you believe that problems likely to have significant impacts only a century hence should be addressed with current technological ways-&-means rather than be deferred for obviating with more advanced means – then you will necessarily prefer active technical management of radiation forcing of the Earth to administrative management of greenhouse gas inputs to the Earth’s atmosphere, for the practical reasons sketched in the foregoing.
Indeed, if credit is properly taken for improved agricultural productivity resulting from increased CO2 and decreased solar UV fluxes – and human dermatological health benefits are likewise properly accounted for – we expect that the net economic “cost” of radiative forcing management will be seen to be extraordinarily negative, perhaps amounting to several hundred billions of dollars each year, worldwide, as suggested.
The more spectacular sunrises and sunsets and the bluer skies will be non-economic “collateral benefits.”