By Betsy Mason
For decades, climate scientist David Keith of Harvard University has been trying to get people to take his research seriously. He's a pioneer in the field of geoengineering, which aims to combat climate change through a range of technological fixes. Over the years, ideas have included sprinkling iron in the ocean to stimulate plankton to suck up more carbon from the atmosphere or capturing carbon straight out of the air.
Solar geoengineering would involve injecting reflective aerosols from high-altitude planes into the layer of the upper atmosphere known as the stratosphere, which stretches between 10 to 50 kilometers (6 to 31 miles) above Earth's surface. The idea is that the aerosol particles would reflect a small amount of sunlight away from the planet, reducing the amount of heat trapped by greenhouse gases and mitigating some of the effects of climate change.
The planned Stratospheric Controlled Perturbation Experiment will send a balloon carrying scientific instruments in a gondola into the stratosphere. The instruments will release a small amount of material — likely ice or mineral dust — to form a kilometer-long plume of aerosol particles (left). Modified airboat propellers will allow the gondola to maneuver above the plume (middle) and lower instruments into the plume to take repeated measurements of how the particles spread through the stratosphere (right). ADAPTED FROM J.A. DYKEMA ET AL / PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A 2014
David Keith envisions using multiple approaches to combat climate change. The red line shows how the impacts of climate change would worsen with a business-as-usual scenario of unabated burning of fossil fuels and other greenhouse gas emissions. Aggressively cutting emissions bends that curve, and removing carbon from the atmosphere offers further cuts, but there are still consequences from the already high levels of carbon dioxide. In this scenario, solar geoengineering would lessen the impact from existing atmospheric carbon dioxide, effectively carving the top off the curve.<p>Some people think we should use it only as a get-out-of-jail card in an emergency. Some people think we should use it to quickly try to get back to a preindustrial climate. I'm arguing we use solar geoengineering to cut the top off the curve by gradually starting it and gradually ending it.</p><p><strong>Do you feel optimistic about the chances that solar geoengineering will happen and can make a difference in the climate crisis?</strong></p><p>I'm not all that optimistic right now because we seem to be so much further away from an international environment that's going to allow sensible policy. And that's not just in the US. It's a whole bunch of European countries with more populist regimes. It's Brazil. It's the more authoritarian India and China. It's a more nationalistic world, right? It's a little hard to see a global, coordinated effort in the near term. But I hope those things will change.</p>
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