David Keith wants to spray a pollutant into the sky to block some sunlight. He says the benefits would outweigh the danger. David Keith wants to spray a pollutant into the sky to block some sunlight. He says the benefits would outweigh the danger. Keith, David W, Geoengineering, Content Type: Personal Profile, Global Warming, Greenhouse Gas Emissions, University of Chicago, Harvard University, Research, Carbon Dioxide, Earth, Sulfur and Sulfur Compounds, University of Calgary NYT > Science