Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session Q7: Is Geoengineering a Possible Stop-Gap Measure to Rapid Climate Change? |
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Sponsoring Units: FPS Chair: Barbara Levi, American Institute of Physics Room: Governor's Square 12 |
Monday, May 4, 2009 10:45AM - 11:21AM |
Q7.00001: Solar-band Climate Engineering Technologies, Risks and Unknowns Invited Speaker: The combination of high inertia and high uncertainty makes the coupled climate-economic system dangerously hard to control. If the climate's sensitivity is at the high end of current estimates, it may be too late to avert dramatic consequences for human societies or natural ecosystems even with immediate and aggressive mitigation efforts. The engineered alteration of planetary radiation budgets--geoengineering--offers and means of managing climate risk, but entails a host of new risks. Most discussion of geoengineering has focused on the injection of sulfur particles into the stratosphere. I will consider the physics of engineered particles, and in particular the possibility of designing self-levitating particles that exploit photophoretic forces, enabling more control over particle distribution and lifetime than is possible with sulfates, perhaps allowing climate engineering to be accomplished with fewer side-effects. Finally, I will discuss options for phased deployment of geoengineering to manage risks and maximize opportunities for learning by doing. [Preview Abstract] |
Monday, May 4, 2009 11:21AM - 11:57AM |
Q7.00002: The Many Problems with Geoengineering Using Stratospheric Aerosols Invited Speaker: In response to the global warming problem, there has been a recent renewed call for geoengineering ``solutions'' involving injecting particles into the stratosphere or blocking sunlight with satellites between the Sun and Earth. While volcanic eruptions have been suggested as innocuous examples of stratospheric aerosols cooling the planet, the volcano analog actually argues against geoengineering because of ozone depletion and regional hydrologic and temperature responses. In this talk, I consider the suggestion to create an artificial stratospheric aerosol layer. No systems to conduct geoengineering now exist, but a comparison of different proposed stratospheric injection schemes, airplanes, balloons, artillery, and a space elevator, shows that using airplanes would not be that expensive. We simulated the climate response to both tropical and Arctic stratospheric injection of sulfate aerosol precursors using a comprehensive atmosphere-ocean general circulation model, the National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE. We simulated the injection of SO$_{2}$ and the model converts it to sulfate aerosols, transports them and removes them through dry and wet deposition, and calculates the climate response to the radiative forcing from the aerosols. We conducted simulations of future climate with the Intergovernmental Panel on Climate Change A1B business-as-usual scenario both with and without geoengineering, and compare the results. We found that if there were a way to continuously inject SO$_{2}$ into the lower stratosphere, it would produce global cooling. Acid deposition from the sulfate would not be enough to disturb most ecosystems. Tropical SO$_{2}$ injection would produce sustained cooling over most of the world, with more cooling over continents. Arctic SO$_{2}$ injection would not just cool the Arctic. But both tropical and Arctic SO$_{2}$ injection would disrupt the Asian and African summer monsoons, reducing precipitation to the food supply for billions of people. These regional climate anomalies are but one of many reasons why geoengineering may be a bad idea. I also discuss 19 other reasons. Global efforts to mitigate anthropogenic emissions and to adapt to climate change are a much better way to channel our resources to address anthropogenic global warming. [Preview Abstract] |
Monday, May 4, 2009 11:57AM - 12:33PM |
Q7.00003: Recent Results from Iron Enrichment Experiments: Implications for Geoengineering Invited Speaker: The oceans play a key role in cycling carbon and are responsible for about half the photosynthesis on the planet. Ice core records tie to changes in marine production changes in climate and recent experiments suggest iron availability covaries with marine production over the last several glacial-interglacial transitions. Several open ocean iron enrichment experiments have recently been conducted to test this linkage directly and findings from these groundbreaking experiments will be presented. Together these results unequivocally demonstrate the pivotal role iron plays in controlling community structure and growth and the uptake of CO$_2$ in major ocean regions. The combustion of fossil fuels has increased atmospheric carbon dioxide approximately 100 ppm above preindustrial levels and has become a major environmental concern. The question of purposeful iron fertilization to control climate is gaining considerable attention partly due to the results of these experiments and the fact that iron is inexpensive and can leverage massive carbon uptake. In addition, the resultant blooms of phytoplankton reduce ocean acidification. What remains to be tested is whether iron fertilization would create unintended and negative consequences to ocean ecosystems. In this talk, both the theory, practice and results of iron fertilization experiments will be presented together with a discussion of some possible negative impacts. Natural iron inputs have had a major impact on climate in the past when atmospheric carbon dioxide was much less than it is today. The role of iron fertilization as a geoengineering solution to climate change, has yet to be tested and can only be evaluated through experimental manipulations designed for this purpose. [Preview Abstract] |
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