Research by the UCLA atmospheric chemist considers whether tinkering with the stratosphere to slow down global warming is feasible, let alone advisable.

UCLA Today

For more than two decades, atmospheric chemist Richard Turco has been studying geoengineering, the climate engineering techniques aimed at halting global warming by spraying  particles into the atmosphere that reflect some of the sun's heat away from Earth. The idea is inspired by large volcanic explosions that caused a few years of temporary cooling in recent centuries.

Advocates of climate engineering have suggested using high-altitude planes to distribute the particles or spraying them into the atmosphere using giant hoses tethered to massive blimps. The idea of geoengineering has taken on growing urgency among people who fear we no longer have time to stop global warming simply by reducing carbon emissions. Turco's research considers whether tinkering with the stratosphere to slow down global warming is even feasible, let alone advisable.
 
Of all the proposals he’s seen so far, the professor with UCLA's Institute of the Environment and the Department of Atmospheric and Oceanic Sciences, concludes: "It sounds crazy to me." Turco, who speaks with a trace of a Jimmy Stewart accent, sat down with UCLA Today writer Alison Hewitt to talk about his research. Below is an edited Q&A.

What's so unlikely about geoengineering?
 
One of their main proposals is that we will use planes to spray sulfur dioxide vapor into the stratosphere, forming particles that will reflect some of the sun's heat away from the Earth. The idea that you could do this with a few planes is ludicrous. You'd have to build a fleet of specialized aircraft capable of flying at 20 kilometers and carrying huge amounts of toxic material. There is no such plane. You'd need special airports, thousands of these planes, a way to load and store the sulfur – it's not going to be cheap or easy.
 
You say we'd need thousands of planes. Where does a number like that come from?

My colleague, Fangqun Yu, a research professor at the State University of New York–Albany, and I have done simulations. Proposals usually try to mimic the effects seen in volcanic explosions that led to temporary cooling worldwide. To emulate just one modest-sized volcano, you'd need to get 10 million tons of sulfur dioxide into the stratosphere. We can't do it all at once. Say we give it a year, and we put 10 tons on an airplane – that's already a pretty big plane. To get the 10 million tons [distributed] would require a million flights a year, or roughly 3,000 flights per day.
 
What's the allure of geoengineering?
 
It sounds very simple and elegant, especially since nature has done some experimenting with volcanoes, proving that sulfur in the atmosphere can cool the Earth down. It's also portrayed as a sort of fallback, emergency plan: If we can't reduce carbon emissions enough to halt climate change, we can shut off the heating effect of all that carbon with geoengineering, creating a shield around the Earth. It's a seductive, compelling argument for [keeping] the status quo, this idea that we can go about our old carbon ways with nothing to lose. But these ideas aren't credible, and it's not solving the issues associated with the continued build-up of CO2 in the atmosphere.
 
What are the downsides?

You're only solving one part of the problem. Assuming it even works, you've stopped the warming trend. But CO2 is still in the air and getting absorbed by the oceans, which will cause the acidification of the oceans. Coral reefs would disappear, and the whole biodiversity of the ocean would be impacted.
 
Also, no more blue skies. The sulfur in the sky would make it look polluted all the time, a kind of milky-white haze everywhere on Earth. Children won't know what blue sky looks like.
 
All of the sulfuric acid particles will eventually fall to Earth, so there might be acid rain, but that would have a relatively small effect. The sulfur aerosol is very likely to cause significant depletion of the ozone layer, so we'll have less sunlight because of the shield, but more UV radiation.
 
But above all, once CO2 is in the atmosphere, it will stay there for hundreds to thousands of years. Here's what that means: You can never let the shield down, because if you do, that build-up of carbon dioxide would cause the climate to warm up catastrophically and  quickly, far faster than if we allowed it to happen without geoengineering, which might at least give us time to adapt. So that shield cannot fail. We are committed for centuries to maintaining the aerosol shield. We would trap ourselves. It sounds crazy to me to put a system in place that must be maintained for centuries to avert disaster.
 
How much would a geoengineering system like that cost?
 
I estimate the cost at $200 billion every year for the first 50 years, and again, we would have to do this for centuries. I looked at what it would cost to build the planes, the lifetime of the aircraft, how much it costs to maintain a large commercial fleet, the costs of producing, storing and transporting toxic sulfur, housing for the workers who would do all of this, and so on. There are more and more people and groups promoting this as a safe, easy and cheap solution to global warming. But their ideas just don't take into account most of the details.
 
Is geoengineering impossible to organize?
 
Well, $200 billion a year might be affordable if you think about the whole world chipping in. It would have to be run by something like the United Nations. Everyone would have to agree to it because everyone would be affected. Even if we succeeded in preventing further global warming, there will inevitably be a losing side. Some people will be worse off because of storms or droughts and unpredictable changes, so now you're also talking about liability. All kinds of claims could be lodged against the authority operating this system. Who's going to give them insurance to protect them against the lawsuits of the world?
 
What is the danger that a "rogue nation" might unilaterally attempt geoengineering and change the climate without asking?
 
If geoengineering were as easy as some people claim, if it only took a few planes, maybe someone could do that, but in reality it's a huge scheme. If you mean a nation like Iran, they don't have the resources to do anything like this.
 
It would take a big nation like the U.S., or the European Union. Maybe Russia, China or India. Some of these countries already do local and regional weather modification. During the Beijing Olympics, for example, the Chinese seeded the clouds to try and wash pollution out of the air. Russia uses weather modification to coax snow to fall outside of major cities. But for a single nation to take on global geoengineering could be an act of aggression. It would violate international treaties. Then again, if we had a means of fixing the climate, then is doing nothing also an immoral act?
 
Assuming someone could get past all the logistical hurdles such as using planes that don't yet exist, would geoengineering work?
 
People argue that it's very doable, and there's simple physics there, I agree in principle. But we don't know how to do it right yet. We need airplanes that don't exist to put sulfur in the air, and we don't even know how much sulfur. The tricky part is that the sulfur particles evolve and react and change over time. Yet with geoengineering, the goal has to be a steady, reliable state for centuries. This can't be done with one big puff in one place like with a volcano. You have to spray small amounts of sulfur all over every day. You're changing the climate of the whole Earth. If something goes wrong, the climate could become unstable.
 
We found in our calculations that by adding the material continuously, it doesn't act the same as one big volcanic puff. You actually need more sulfur than research on the cooling effects of volcanoes would suggest, because as you add more sulfur, the effect becomes less and less efficient. The particles clump together and don't reflect back as much light. If the particles are too large, that would actually create a warming effect. If you do it wrong, we'll all be cooked.
 
Do you think there's still time to solve climate change by curbing carbon emissions?
 
I don't know that I have much hope that we'll turn this around. A decade or two ago, we said we needed to reduce emissions, and the IPCC [the Intergovernmental Panel on Climate Change, the international body that the United Nations relies on for climate predictions] developed scenarios for how much carbon would be in the atmosphere around the year 2000. We've gone above the most pessimistic prediction they had, and that's even after the Kyoto treaty, even after everyone saying we had to change our ways.
 
This is why geoengineering has taken on a new life. Carbon emissions have gone up much faster than make any sense. No one wants to pay for hard solutions, so the back door is "easy" geoengineering.
 
What are some of the worst suggestions you've heard?
 
I've been studying this more seriously in recent years because of the renewed interest – desperation, really – surrounding geoengineering. There are a variety of schemes. One idea is hydrogen-filled balloons to carry the payload up. Another is a giant hose, tethered to a gigantic blimp in the sky. Some of these ideas are so nutty that they hardly deserve consideration.
 
Consider the idea of a 20 kilometer hose. There is no such hose. The weight of the hose itself – it's completely nutty. Or if you're sending the sulfur up in balloons, how many balloons do you need? How would you deliver the sulfur once the balloons reached 20 kilometers? How would you retrieve the balloons? You'd need thousands of really enormous balloons to lift the tons of sulfur, and they'd be incredibly expensive. One fellow suggested dispersing the sulfur by putting it in the balloon and arranging for the balloon to burst into flames at the proper altitude. Great, you've burned your expensive balloon, and now there are gondolas, thousands a day, crashing to Earth! It's just totally nutty.