Tweaking global warming with science

In my last post I linked to a talk from David Deutsch about the possibility of decreasing the odds of a global increase in temperature (or of some catastrophes associated with it) with science. Well, it looks like Deutsch may be right: promising ideas are coming up from the scientific side.

I’ve heard of cloud seeding before, but only as a means to make it rain where it wouldn’t otherwise. Until I found this article about the research of John Latham, of the National Center for Atmospheric Research in Boulder, US, Stephen Salter, of Edinburgh University, UK, and their colleagues. They propose to spray salt water in low-lying clouds above the oceans to increase their reflectivity to the sun’s light. This could be achieved, they say, with a world-wide fleet of ships dedicated to taking the water from the ocean and spraying it up in the air in huge jets.

Latham and co-workers, including wave-energy researcher Stephen Salter of Edinburgh University, claim that such spraying could increase the rate at which clouds reflect solar energy back into space by as much as 3.7 Wm-2. This is the extra power per unit area that scientists say will arrive at the Earth’s surface following a doubling of the concentration of atmospheric carbon dioxide compared to pre-industrial levels — 550 ppm vs 275 ppm (Phil. Trans. R. Soc. A DOI:10.1098/rsta.2008.0137).

And if that’s not cool enough, they plan to use sailing ships to do the job — but with no sails! Their proposed sips use these things called “Flettner rotors”, which are giant rotating cilinders that use the so-called “Magnus effect” to create a propelling force perpendicular to the airstream. This YouTube video shows the futuristic design of those things:

Now of course, any such geoengineering could have unforeseen consequences, just as our carbon dioxide emissions had in the first place (well, unforeseen is not quite the right word in this case. Scientists have been crying about global warming for decades! Global warming wasn’t as unexpected as the cane toad infestation in Australia). Anyway, diminishing our emissions should still be the first priority, and careful research and tests should be done to ensure the safety of any drastic solutions as these.

But I agree with those guys that we are unlikely to achieve a significant reduction in emissions in time to prevent major consequences, and projects as these, while risky, may be an alternative to see us through if all else fails. And in an emergency, you have to act promptly, with your best guesses, given the analysis of the foreseeable risks. I doubt the risks of this kind of project are as alarming as those of the worst-case scenarios for global warming. And in any case, they could always turn it off instantly if things are not working as planned. So kudos for Latham, Salter et al.! Let’s hope they can make it work!


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