About the discussion on climate, lets' hope that the greenhouse effect
can be avoided. However, as a last resort, in 1988 three scientists
suggested independently that a space screen could be built to deflect
a small fraction of the solar radiation incident on Earth. About 3%
reduction in incident solar radiation was estimated to compensate for a
4 degree increase in temperature. The deflection can be accomplished
by screens in Earth orbit or at Sun-Earth L1 point. An even better low-
tech solution is a dust screen in orbit. This could be launched from the
moon by mag-lev devices similar to those proposed for launching lunar
materials for the colonies. The mass requirements in either case are
1E9 - 1E11 kg, which could be obrained either form lunar or asteroid
resources.
About two years ago a climate simulation study showed that the
screen could indeed achieve the cooling effect.
Detailed designs were published in the Journal of the British
Interplanetary Society and in Nature. The climatic impact of course
needs much more study, but as one of the proposers, I believe that
they will be better than a run-away greenhouse effect that may make
the Earth uninhabitable. Also, deploying the screen will be less
expensive than the economic damage and social upheaval that may
be caused by greenhose warming. Maybe this option for an insurance
against runaway greenhouse effects can add to the motivation for an
infrastructure in space and on the Moon.
If anyone is interested in the details, I will be glad to provide some E-
reprints.
Em Qua 10 Dez 2003 23:29, Michael Mautner escreveu:
> Detailed designs were published in the Journal of the British
> Interplanetary Society and in Nature. The climatic impact of course
> needs much more study, but as one of the proposers, I believe that
> they will be better than a run-away greenhouse effect that may make
> the Earth uninhabitable. Also, deploying the screen will be less
> expensive than the economic damage and social upheaval that may
> be caused by greenhose warming. Maybe this option for an insurance
> against runaway greenhouse effects can add to the motivation for an
> infrastructure in space and on the Moon.
think that it is unlikely to happen. There is evidence that, along Earth's
natural history, there has been major *natural* globs of greenhouse gases
that boosted instantly the temperature of the planet several degrees - much
more than the supposed current human-induced global warming. (See
http://www.gsfc.nasa.gov/topstory/20011212methane.html or
http://www.rochester.edu/pr/releases/ear/champ.htm .) During such events,
sometimes the Earth became *so* hot that there were crocodiles in the Arctic.
Nevertheless, Earth never became another Venus. In fact, I think that Earth is
just too far from the Sun to be really hot; in fact, AFAIR, looking at the
cycle of the Ice Ages, we can see that in fact the normal state of the Earth
seems to be the Ice Ages, and Warm Ages like ours are relatively short
pleasant interruptions.
Lucio Coelho