Cutting emissions isn’t enough: Counteract global warming with geoengineering

With consecutive devastating hurricanes hitting Florida early this fall season, and a new normal of storm damage in the U.S. projected to exceed $100 billion annually, it is time to recognize that our collective efforts to mitigate climate change by shifting to greener energy may not suffice.

Despite making some progress in slowing the growth of emissions, the world continues to emit more carbon dioxide than ever, notwithstanding impressive progress in wind, solar and hydroelectric energy. The planet’s 8 billion people are becoming more prosperous all the time — a good thing overall, but with the predictable result of more energy consumption.

Our transition to clean industry and energy must continue, to be sure. But even if global efforts to cut emissions were redoubled, the world is still in for a lot of costly effects from climate change — rising oceans, changing rainfall patterns, stronger storms, more drought.

Is it time to consider geoengineering or climate engineering — artificially cooling the planet — more seriously? The idea has been floated for at least a half century now, and taken seriously by some forward-looking thinkers for a couple decades. But with global temperatures now more than 1 degree Celsius above pre-industrial levels (about 2 degrees Fahrenheit), and likely headed for 2 degrees Celsius in coming decades — a level widely recognized as dangerous — the answer may be yes.

The cost of severe climate impacts might be lowered, possibly a lot, with active planetary cooling efforts. Even if every country doesn’t come to that conclusion, climate perils could become so great that some vulnerable countries, from Pakistan to various island nations around the world, might take matters into their own hands and start engineering the planet.

Even a wealthy individual could try to achieve this outcome unilaterally. That would not be the preferred route; we need a better way to think about how to put Earth’s collective hand on any such future planetary thermostat.

Yes, any effort at partial global cooling would involve messing with Mother Nature. We need to be very careful about this idea, and learn much more before we do it. But, of course, we are already messing with the planet though our carbon dioxide and other emissions. The National Academy of Sciences, in a major 2021 study, has called for more serious research, including government funding, to complement and expand upon the modest experiments that have been done by others.

There are numerous ideas for how to cool the planet. Most interesting to me is the “natural experiment” that has already been done with volcanic eruptions — to put enough sulfur dioxide into the upper atmosphere that a very modest percent of incoming sunlight is reflected back to space. Mount Pinatubo in the Philippines was the last significant example of this, in 1991. In 1815, Mount Tambora in Indonesia erupted, leading to a “year without summer” in 1816. Temperatures in the U.S. and Europe were several degrees below normal; crops died and famine occurred as a result. That experience reminds us we mustn’t overshoot; great care is needed in any effort at climate modification.

By watching these natural experiments and doing some of our own, we can figure out how to calibrate any future artificial change in temperature. When it comes to cost, the option of high-altitude aircraft dispensing particles seems to be the cheapest, but nobody is sure, because adequate experimentation hasn’t been done. Air currents would help ensure that the particles diffused around the planet, affecting the whole world’s climate.  

There are risks with this approach. Some studies suggest that monsoons may be affected — if that happens, or if people think it is happening, finger pointing will begin.

Even as such dramas unfold, nothing about doing such climate engineering for perhaps a few decades should lessen our commitment to slashing pollution from the industrial and energy systems of today. Climate engineering is unlikely to work perfectly, and the more climate warming that we have to mask, the greater the potentially harmful side effects. On top of that, the buildup of carbon dioxide doesn’t just cause climate warming — it also acidifies the oceans, which can cause havoc in ecosystems. Reversal of some warming doesn’t stop the acid.

In addition to doing more experimentation, there are political issues to explore as well. It may soon be time to begin preliminary discussions in multilateral forums about how any attempt at climate engineering might be coordinated and supervised.

Who would make the decisions about climate engineering? The deciding body clearly needs to be representative of all major groups of countries, yet without a veto power for any one country. The U.N. Security Council is weighted too heavily towards the established industrial powers — the very countries that largely created the problem. Something else is needed for this purpose. Perhaps this body should make future decisions based on some kind of supermajority vote.

Then there is the question of how much cooling to attempt. It would probably make sense to take something significant and simple; we don’t want to overshoot the mark and cool the planet relative to pre-industrial temperatures. So maybe we should aim to reduce the world’s temperature by 1 degree Centigrade, since by the time any decision might be made (in the 2030s?), temperature rises may well have reached 1.5 degrees.

Then there is the question of cost. It seems logical that wealthy industrialized countries that have emitted the most carbon dioxide should pay the most. In fact, I’d argue we should together pay for the whole thing, in keeping with the spirit of the Paris climate accords. The costs would include those for cooling the planet and compensating any communities or countries that suffered adverse consequences.

There will be a lot to sort out and develop consensus about if this kind of idea is ever attempted. All the more reason to get started now, both with experimentation and with initial international dialogues over how any future climate engineering should be undertaken.

Michael O’Hanlon is the Phil Knight Chair in Defense and Strategy at the Brookings Institution and author of “Military History for the Modern Strategist: America’s Major Wars Since 1861.”