As California Governor Jerry Brown’s Global Climate Action Summit is underway in San Francisco, we look at one of the more controversial solutions to climate change: geoengineering. Sometimes called “climate manipulation,” geoengineering involves the deliberate altering of the earth to decrease the impact of greenhouse gas emissions. Such proposals are already being explored by government agencies, scientists, and businesses around the world. Supporters of geoengineering endorse radical ways to manipulate the planet, from spraying aerosols with sulfur particles into the stratosphere, to scrubbing carbon dioxide from the atmosphere. But critics say these “techno-fixes” do nothing to address the root causes of climate change, and worse, can be dangerous for the earth. We host a debate between Gopal Dayaneni, board member of the ETC Group and a founding member of the Climate Justice Alliance, and David Keith, professor of applied physics at Harvard’s School of Engineering and Applied Sciences and professor of public policy in the Harvard Kennedy School. He is also the founder of Carbon Engineering, a company developing technology to capture CO2 from ambient air.