(This is an updated version of part 3 in our series featuring Dr. Teller's vision of how to deal with unwanted climate change, excerpts from pages 6-7. For the entire series, click Dr. Edward Teller link)
Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change (PDF)
Edward Teller, Roderick Hyde and Lowell Wood
This article was submitted to the
National Academy of Engineering Symposium
April 23 – 24, 2002
Ways-&-Means For Active Management Of Radiative Forcing
‘Covering’ of the order of 1 million km2 of the Earth’s area with something that substantially affects the sunlight falling on it – or the Earth’s thermal re-radiation from it – might appear to be a rather ambitious task.
However, since matter may be made to interact quite strongly with radiation, if its composition and geometry are properly chosen, the principal challenge is not the preparation or handling of the quantities of materials involved in this ‘cover’ but rather the ensuring that they will stay in place for usefully long intervals.
(image left from euronuclear.org)
As a specific example and looking ahead to one of our results, the present concern about global warming centers on the inputting of about 7 billion tonnes of carbon into the atmosphere each year and several times this level several decades hence; the annual deployment of barely 0.01% this mass of sulfur – roughly one ten-thousandth as much sulfur as carbon – in appropriate form and location can be made to entirely offset the “greenhouse effect” of the ten-thousand-fold greater mass of added CO2.
(image right from University of Nebraska, click image for detail)
We have examined such considerations in a little detail, and the summary of our earlier results is as follows.
From a basic physics viewpoint, materials vary strongly in their ability to interact with and thus to manipulate optical-spectrum radiation, with resonant scatterers having the greatest mass efficiency by far, good metals having about 10,000 times less specific radiative-interaction efficiency than resonant scatterers, and typical dielectrics having about 1% the specific radiative-interaction power as do the best metals.
Each of these classes of materials offers distinct, independent, eminently practical ways-and-means of accomplishing the technical management of radiative forcing; some of these are old, but several of them are novel.
We’ll briefly review a sampling of both old and new types.
Positioning of scatterers of incoming solar radiation in the Earth’s upper atmosphere – specifically, the middle to upper stratosphere – is a now-venerable approach that appears to provide the most practical deployment, as operational lifetimes of such engineered scatterers can be as long as a half-decade; required replacement rates are correspondingly modest.
Thus, the stratosphere is where we propose to deploy all of the insolation-modulation scattering systems that we propose for near-term study. (image right of stratospheric ozone, from NOAA)
Optimized formation and emplacement of sulfate aerosol is the most mass-costly – albeit a reasonably dollar-economical – means of scattering back out into space the sunlight fraction needed to offset the predicted effects of atmospheric CO2 concentration in the year 2100. (image left of sulfur levels in atmosphere, from umich.edu, click image for detail)
Interestingly enough, such Rayleigh scattering of sunlight, performed by stratospherically-deployed aerosols whose diameters are several-fold smaller than the wavelength of light itself, will selectively scatter back into space the largely deleterious ultraviolet component of sunlight while diminishing the light that we see – and that plants use for photosynthesis – only imperceptibly. (image right from wikipedia.com)
From the human perspective, skies would be bluer, twilights would be more visually spectacular, plants would be less stressed by UV photodamage and thus would be more productive, and children playing out-of-doors would be much less susceptible to sunburn (and thus to skin dysplasias and dermal cancers as adults), if this stratospheric Rayleigh scattering system were to be deployed.
We’ve estimated the dollar-outlay cost of such active management of radiative forcing on the year-2100 scales to be about $1 B[illion]/year, and no one to our knowledge has taken issue with this scooping-level estimate since we offered it a half-decade ago.
Indeed, the National Academy study implicitly acknowledged the practicality of this type of approach, although it considered only thoroughly non-optimized dielectric aerosol scattering.
Incidentally, such costs appear to be an order-of-magnitude less than health-care savings in the U.S. alone due to avoidance of UV skin damage – and far less than increased agricultural productivity due to avoidance of crop photodamage in the U.S. alone; thus, the cost to the U.S.taxpayer of implementing this system of benefit to all humanity would appear to be quite negative: its economic benefits would greatly outweigh its economic costs.