Last Wednesday night, as I watched the climate discussions with each of the Democratic Party candidates on CNN’s Presidential Climate Town Hall, I kept asking, “Why is only Andrew Yang talking about solar geoengineering?”
True, he is the most tech-savvy of the candidates, but all of them need to understand the various scientific solutions we have – and don’t have.
All the candidates get the idea of replacing fossil fuels, but none of them understand the magnitude of this solution or the time and money required to do it.
For the U.S. alone, it will cost about $10 trillion over 20 years. Without nuclear, that cost doubles to $20 trillion over 30 years. For the world, it will cost US$65 trillion – without nuclear it will cost over $100 trillion. These are not trivial numbers and are unlikely to get spent in time to help. Which is why we need solar geoengineering.
Solar geoengineering is the process by which humans deliberately reduce the effect of heat-trapping greenhouses gases by reflecting a small fraction of sunlight back into space.
It sounds strange, but it isn’t as odd, or as difficult, as it might seem. And we know that it works because it happens every time a huge volcano erupts. And we’ve been studying those for over 100 years.
Some serious scientific mojo has been applied to this idea at universities around the world. Harvard’s Solar Geoengineering Research Program is a research initiative devoted entirely to the science, technology and public policy of solar geoengineering.
But too few scientists, and too little funding, has been applied to this solution. Which is sad since it doesn’t need much.
There are several technologies for this approach, including injection of aerosols (fine droplets or particulates as fine as powder) into the stratosphere, where they would scatter some sunlight back to space, thus cooling the planet by reducing the amount of heat that enters the lower atmosphere (see figure).
Marine cloud brightening is another way to reflect solar radiation back into space. This would use automated ships to spray droplets of seawater into the atmosphere above the ocean where they evaporate to form an elevated concentration of sea-salt aerosols which seed higher concentrations of cloud droplets in clouds over the ocean, increasing their reflectivity (see figure).
According to one the fields long-time researchers, Dr. David Keith at Harvard, solar geoengineering could limit global warming’s predicted side effects such as sea level rise and changes in precipitation and other weather patterns. Because these changes would have their most powerful impact on the world’s most vulnerable people, who lack the resources to move or adapt, Keith finds a strong ethical case for research into solar geoengineering.
Besides, we’ve been geoengineering the atmosphere for over a century - in the wrong direction – by injecting huge amounts of CO2 and other greenhouse gasses into the atmosphere.
Let’s face it. As a species, we just have not risen to the occasion of fighting the planetary crisis of global warming. And by all measures we’re not going to. Global emissions are continuing to rise. Oil and gas keep getting cheaper and easier to find, and coal is the easiest energy source to emplace in a poor country with little infrastructure.
To bring this home, all you have to do is see how climate scientists are seeking psychiatric help for the depression, anxiety and PTSD that happens when you see a train wreck coming but no one seems to want to do anything about it - and you’re on the train.
And America seems to have gone on a carbon binge. We’re producing more oil, gas and coal than any other country, and more than ever before. Along with trying to repeal over 80 environmental rules going back to the Nixon Administration, the Trump Administration has moved to eliminate federal curbs on methane emissions from oil and gas operations.
Even the oil companies don’t want this.
Prior to the United States pulling out of the Paris climate accords, there was growing skepticism that the world could, or would, decrease its total greenhouse gas emissions by 2040 enough to actually prevent the worst of global warming.
All climate models show that the next 20 years is critical. The best we can do is keep warming to 3 to 4°F, and that only if we get global emissions to zero by 2040. If we don’t, temperatures rise by 6 to 8°F. That’s because CO2 has a half-life in the atmosphere between 30 and 300 years, depending on the various chemical mechanisms that naturally remove CO2 from the atmosphere.
And that’s just the half-life.
We have to start reducing emission now by almost 10% per year until 2040 when anthropogenic emissions will have to be zero. We are extremely unlikely to meet this target - global emissions are still growing and it looks like we will not even start declining for at least 10 more years. At that time we would have to reduce emissions by 20% per year.
Let me state that clearly – there is no way to reduce carbon emissions in the next 20 years sufficient to mitigate the worst effects of climate change.
This is sobering indeed. But don’t get too bummed because it’s not the end. Many scientists have wondered how to either remove GHGs from the atmosphere or mitigate the effects some other way. Indeed, an entire scientific discipline has evolved around this issue and some great work has been done.
Removing GHGs is really difficult and really expensive. Much more expensive than preventing them from entering in the first place. So if we refuse to spend the amount of money and effort needed to reduce emissions, we certainly wouldn’t spend even more trying to get them back out. But we still need to try.
The other strategy is to mitigate the effects of warming by directly cooling the planet. Cooling occurs naturally when millions of tons of particles such as soot from huge fires, particulates and gasses from large volcanic eruptions, or excessive amounts of ice crystals, enter the atmosphere and either block incoming solar rays or reflect them back into space.
Enter Solar Geoengineering.
Solar geoengineering should not replace reducing emissions (mitigation), coping with a changing climate (adaptation), or carbon dioxide removal and sequestration. Solar geoengineering does not change the CO2 concentrations in the atmosphere, it treats a symptom - heat.
It’s like putting some serious sunblock on Planet Earth, giving us time to figure out how to lower our carbon emissions to near-zero.
Changing the Earth’s albedo, or reflectivity, is what these strategies target. Lower albedos capture and hold solar radiation, higher albedos reflect it back.
Speaking as a geologist, we have seen the cooling effects of big fires and big volcanoes in the geologic record going back many millions of years, so we know it works, and how it works. When the huge volcano Krakatoa erupted in 1883, the billions of tons of particulates thrown into the stratosphere dropped global temperatures about two degrees. But as the particulates came out of the atmosphere over the next few years, the effect went away.
But these natural processes are uncontrolled and in many cases cause very big adverse environmental changes themselves. Of course, the particulates and gases coming out of a volcano are not the ones we would choose in solar geoengineering.
And that’s the whole point of research, says Dr. Tom Ackerman at the University of Washington Department of Atmospheric Sciences. Because we have studied large volcanic eruptions like Krakatoa, Tambora and Pinatubo, there aren’t any real basic science unknowns. We know that stratospheric aerosols can achieve cooling that offsets half of the warming from a doubling of CO2 concentrations.
It’s just figuring out how to do it effectively without causing other problems.
By choosing where to release the aerosols, a uniform global aerosol layer could be created. Its thickness could be varied as needed - thicker at high latitudes or in one hemisphere or the other - in order to craft a desired outcome. Within certain limits.
As Keith describes, solar geoengineering has three essential characteristics: it is cheap, fast and imperfect. Long-established estimates show that solar geoengineering is at least 100 times cheaper than cutting emissions in offsetting the expected global temperature rise through 2100.
A few grams of particles in the stratosphere can offset the radiative forcing of a metric ton of atmospheric carbon dioxide. At about US$1,000 a metric ton for aerosol delivery, that adds up to maybe a billion dollars per year, not the trillions of dollars it will take to replace all fossil fuels with hydro, nuclear and renewables.
And $50 to $100 million a year for about 10 years is all it would take to do the research needed to figure out how to do this right. That’s barely the cost of a single fighter jet, not much for saving the planet and half the species on it.
Not to fund this research program is like being too cheap to buy sunblock, knowing skin cancer runs in your family.
This research will answer a lot of things, even the ethics questions of whether we should do it at all. But if you don’t do the research in the next ten years, you may not be able to implement this correctly when you realize we need to do this fast. And others may do it anyway, without the care we might show.
The Chinese have specifically said they will do exactly this if things get too out of hand with global warming. And they have a robust research program already underway.
As Joseph Lassiter of Harvard calculates, “Assuming humanity continued to make a net addition of CO2 into the atmosphere every year for a decade, and some of the sulfate aerosol shield would dissipate every year, continuous injections of greater amounts of sulfates would be needed each year in order to maintain the concentration required to manage the earth’s temperature.”
For example, in the first year it would take about 25,000 metric tons of sulfates dispensed by 1 or 2 aircraft to offset about 50% of that year’s increase in warming. In order to maintain the 50% reduction, in year two, about 50,000 tons of sulfates would need to be dispensed and so on each year into the future. After 10 years this number would reach over a million metric tons of sulfates dispensed by 100 aircraft.
This is still not much. And we should finally start decreasing carbon emissions after 2030, decreasing over the next few decades until we no longer need solar geoengineering.
Let’s be clear - solar geoengineering is not to be done, or even considered, as a replacement for cutting carbon emissions. It’s just to buy us the several decades we need to actually cut emissions to near zero without frying the planet.
This is because solar geoengineering cannot eliminate all of the damages caused by green-house gas-driven warming, even if it tried to restore global average temperatures to pre-industrial levels. Compared to the warming caused by GHGs - which trap long wave radiation - climate variables such as temperature and precipitation respond differently to cooling caused by solar geoengineering which reflects short wave radiation.
For example, if temperatures were restored to pre-industrial levels by solar geoengineering, the water cycle would be weaker than it was in the 1700s.
An important point to remember about solar geoengineering is that it inherently self-limiting. You have to keep doing it continuously until we get a handle on emissions. If you stop, the effect goes away in a year or two as the aerosols come out of the atmosphere, just like happens a few years after every huge volcanic eruption.
But this turns out to be a good thing. Solar geoengineering can be adjusted easily and relatively quickly, even reversed, if you don’t like the effects. We wouldn’t have to accept even a few degrees temperature increase, we could keep it the way we want it, even cool off a bit back to where we were 100 years ago.
As Keith puts it, “Because the warming impact of carbon is more or less forever [on biological lifetimes], all that we can achieve this century by cutting emissions is to stop making the problem worse. Solar geoengineering allows a more optimistic outcome. In combination with technologies to remove carbon that is already in the atmosphere, it would allow humanity to aim to restore the preindustrial climate over two human lifetimes.”
And we do have technologies to remove and capture CO2 from the atmosphere, the ocean and the fossil fuels being burned. It just will take some time for them to have a global impact and to decide where to put the CO2.
So what would we put into the atmosphere? Many materials have been looked at, including alumina, diamond dust and bismuth tri-iodide, all with a hope of decreasing unwanted side-effects like ozone depletion that may occur with sulfur.
I like calcium carbonate particles, basically ground up limestone or sea shells. They are not toxic, don’t appear to harm the ozone layer, and as they fall into the ocean they would help mitigate ocean acidification a bit.
Critics worry that solar geoengineering could have unintended consequences, like sulfate damaging the ozone layer, and that focusing on this type of response is a distraction from the better response of decreasing carbon emissions. Even fears of military misuse crop up.
But these are the questions that would be answered by a serious research program.
Peter Frumhoff of the Union of Concerned Scientists mused that “Solar Engineering is the emergency room response to climate change. We need to have it ready but we hope never to use it. Preventive medicine is always better.
But we have failed on the preventive medicine side of global warming. Standing next to an accident victim in the ER saying they need a better diet and exercise isn't helpful.
Fossil fuel use is climbing as fast as ever worldwide, mainly in the developing world. And we in the developed world have failed at helping them find alternative energy sources.
Like many epic questions of the future, it would be wise to do our due diligence before we are forced into radical actions.
A big question, of course, is whose hand would be on the thermostat?
Date: Sep 10, 2019