Lecture 23

Lecture 23 - SIO 40 – Life and Climate on Earth Nov 30 2009 Lecture 23 – Mitigating global warming Part I Geo-engineering approaches Geo ‐

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Unformatted text preview: SIO 40 – Life and Climate on Earth Nov. 30, 2009 Lecture 23 – Mitigating global warming, Part I Geo-engineering approaches Geo ‐ engineering Solutions (?) eo-engineering is an approach to mitigating global warming that involves using technology to ounteract climate change impacts either at the source level (ie. doing something about growing reenhouse gas levels) or at the impact level (ie. offsetting climate change itself). These approaches involve planetary-scale environmental engineering, the likes of which society has not yet seen. Recommended Reading http://www.theatlantic.com/doc/200907/climate-engineering The above illustration from the recommended article shows an artist’s depiction of a scheme to inject sulfate aerosols into the stratosphere to cool the Earth. The idea of purposely injecting sulfur dioxide into the stratosphere to cool the planet is based on the knowledge that volcanic injection of SO 2 into the stratosphere (above left) results in the formation of sulfate aerosols which can reduce transmission of solar radiation through the atmosphere (above right). Would it work? We already have some data….. lobal mean temperature changes for 5 years preceding and following a large volcanic eruption (at year zero). Data are average changes noted for 5 major eruptions: Krakatau, Santa Maria, atmai, Agung, and El Chicon. These averages suggest a global cooling of 0.3-0.7 ° C for 1-3 ears following an eruption. Cooling due to volcanic eruptions Concerns about sulfate aerosol addition While aerosols themselves do not destroy ozone, interaction of aerosols with chlorine in the stratosphere due to CFC’s can have a detrimental effect on ozone levels, as observed following the eruption of Mt. Pinatubo (above). Some worry that purposeful addition of sulfate aerosols to the atmosphere to counteract global warming could have unforseen negative effects on ozone. Other concerns relate to acid rain and unpredictable shifts in rainfall caused by the aerosol addition, which could adversely affect climate in some regions. Schemes to increase Earth’s albedo Some geo-engineering schemes are targeted at increasing Earth’s overall albedo, thus reflecting more solar energy back into space rather than absorbing it. One such idea, pictured above, would involve fleets of up to 1500 ships that would cruise the oceans, sucking up seawater and spraying it into the lower atmosphere. This would increase cloud albedo over the oceans. Other ideas related to albedo include wrapping reflective “blankets” around glaciers, or floating reflective surfaces over large areas of the oceans. Schemes to reduce incoming solar radiation rom the Atlantic article: “Roger Angel, an astronomy and optics professor at the University of Arizona,...
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This note was uploaded on 10/23/2010 for the course SIO SIO 40 taught by Professor Barbeau during the Fall '10 term at UCSD.

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Lecture 23 - SIO 40 – Life and Climate on Earth Nov 30 2009 Lecture 23 – Mitigating global warming Part I Geo-engineering approaches Geo ‐

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