Weather Break

From the Creighton University Department of Atmospheric Sciences

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Geoengineering Low Clouds

July 21st, 2009 · No Comments

Click here to listen to episode 562 of Weather Break.

All this week on Weather Break, we’re tackling the subject of geoengineering. Geoengineering is this idea that mankind can use technology to make big changes to the climate of the Earth as a deliberate way to address the problems associated with Global Warming. The plan that we talked about yesterday involved adding sulfur to the stratosphere. We know from experience with volcanic eruptions that the planet gets cooler when sulfur is injected into that part of the atmosphere because the sulfur reflects sunlight back up into space before it is able to warm the surface of the Earth.

Another geoengineering idea that is being kicked around is this idea of using low clouds over the oceans as a way to cool the planet back down by a few degrees. Clouds, of course, are white–they reflect much of the sunlight that hits them, keeping the surface a bit cooler. As it happens, the kinds of low clouds that form over certain parts of the world’s oceans are slightly less white than you might think. The reasons for this are a bit technical–it has to do with the fact that these oceanic clouds are composed of a relatively small number of fairly big drops of water, whereas the clouds that you and I are familiar with are made up of vastly larger numbers of very tiny drops. The result is that the low clouds over the ocean really aren’t quite as white and therefore actually do reflect a little less sunlight than other clouds do.  It turns out that it is surprisingly easy to made chemical and physical changes in these low clouds to change just how white they really are.  Could mankind fine-tune the behavior of low clouds to regulate the temperature of the Earth like a thermostat?  And what would the consequences of a plan like this be?


Much of the information in today’s episode of Weather Break was based on materials available in this article from Scientific American.

Mankind already changes the whiteness (or “albedo”) of low clouds over the ocean through what are called “ship tracks”.  For more information about ship tracks and pictures of these clouds from space, visit NASA (or this page from NASA), ScienceBits, the University of Wisconsin, or Wikipedia.

Tags: Climate Change · Geoengineering

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