The discussion on how to control the out-of-control climate has always seemed to me somehow out of whack. Climate doctors invariably focus on changing our energy sources, but pay little attention to how to cool this rapidly overheating planet. And that is the presenting problem.
Dr. David Keith, a professor of applied physics and of public policy at Harvard, finally addresses this crucial issue in “What’s the Least Bad Way to Cool the Planet?” He offers what will be to many a new framework for addressing our most immediate urgency.
Eliminating emissions by about 2050 is a difficult but doable goal. Suppose it is achieved. Average temperatures will stop increasing when emissions stop, but cooling will take thousands of years as greenhouse gases slowly dissipate from the atmosphere. Because the world will be a lot hotter by the time emissions reach zero, heat waves and storms will be worse than they are today. And while the heat will stop getting worse, sea level will continue to rise for centuries as polar ice melts in a warmer world.
Keith’s conclusion is that we need both to stop carbon emissions and find ways to cool the planet. To do the latter we need some form of social geoengineering, likely in the form of reflecting sunlight. As another report notes, such technologies will likely involve “adding small reflective particles to the upper atmosphere, by increasing reflective cloud cover in the lower atmosphere, or by thinning high-altitude clouds that can absorb heat.” The report acknowledges that there may be “an array of unknown or negative consequences.” And many critics have focused on these. Others have tried to account for them.
The other way to reduce heat is by using carbon removal (capturing it from the air) technologies. This, it seems to Keith, is far less feasible, considering the scale and time required to bring it about.
Planting sufficient trees would require a lengthy and immense transformative effort. Industrial removal methods must confront the challenge that there is just too much carbon to remove from the air in too short a time. The technology is nowhere in place.
The challenge is that a carbon removal operation—industrial or biological—achieves nothing the day it starts, but only cumulatively, year upon year. So, the faster one seeks that one degree of cooling, the faster one must build the removal industry, and the higher the social costs and environmental impacts per degree of cooling.
Geoengineeering—e.g., putting sulfur particles into the stratosphere—sounds “reckless,” says Keith, and will surely exacerbate some climate changes, but
the harms that would result by shaving a degree off global temperatures would be small compared with the benefits. Air pollution deaths from the added sulfur in the air would be more than offset by declines in the number of deaths from extreme heat, which would be 10 to 100 times larger.
And, of course, the “grand challenge is geopolitical.” What countries would get to decide on such a course and execute it? And for how long? Carbon removal is the safest path, but “solar geoengineering may well be able to cool the world this century with less environmental impacts and less social and economic disruption. Yet no one knows, because the question is not being asked.”
More research, and there is very little now, is essential. “Cooling the planet to reduce human suffering in this century will require carbon removal or solar geoengineering or both.”