But even considering such an endeavor raises many practical, economical, political and ethical questions, experts said, including what the effects on global and regional climates would be.
“I’m not in favor of doing it today. I’m agnostic about whether we should ever do it,” said Alan Robock, a distinguished professor of environmental sciences at Rutgers University. “We don’t have enough information and, in any case, we don’t have the technology.”
But Robock said additional research should be conducted despite concerns that determining the feasibility of such “geoengineering” might encourage a government or wealthy individual to try it, and could lessen efforts to curb greenhouse gases such as carbon dioxide.
“I don’t think you can just ignore it and pretend it doesn’t exist, and sometime in the future, when someone becomes scared and wants to do it, they don’t even know whether they can do it,” he said.
Mount Pinatubo’s eruption sent an estimated 20 million tons of sulfur dioxide and ash into the stratosphere, where the sulfur dioxide formed sulfate particles that reflected sunlight back into space. Some believe this could be done effectively and at relatively low cost by injecting an aerosol of sulfur dioxide or some other gas into the atmosphere over a period of time, either from aircraft or powerful missiles.
Ken Caldeira, a senior investigator for the Carnegie Institution for Science, told a congressional committee in 2009 that such methods are inexpensive, can be deployed quickly, and probably would cool the Earth effectively. He stressed, however, that it is more important to address the root cause of global warming by reducing the production of greenhouse gases. Carnegie will host a panel discussion on the subject Tuesday evening.
But Robock, in an interview, said the effort is “not feasible. No technology exists to do solar radiation management. There are no airplanes, or hoses or missiles that exist to get sulfur up into the stratosphere.”
A more limited variation of the idea is to spray sea salt into clouds over the ocean, probably from ships, to form more water droplets in the clouds and make them whiter, said Lynn Russell, a professor of atmospheric chemistry at the Scripps Institute of Oceanography, which is part of the University of California at San Diego. The brighter clouds would reflect more sunlight.