Carbon Removal or Sunlight Reflection?

Time to Act Unconventionally to Address Climate Change

Sometime in the mid-2000s, I can’t remember precisely when, I attended a conference in Colorado at which many of the world’s leading climate scientists and economists presented their climate change projections, and costs and benefits of various measures for addressing the adverse consequences of climate change. As best as I can recall, there was consensus that things were going to get worse, but some disagreement about what policies to take.

On the last panel of the conference, one or two scientists made a compelling case for an idea that, up to then, I had never known about. Although most of the expert attendees seemed to dismiss the idea as being too risky, or even crazy, I had a totally different reaction: cautious, but intense interest.

This (then) far-out idea was called “geo-engineering” – having airplanes continuously spray sulfates into the upper atmosphere, which would reflect sunlight and thus cool the earth, offsetting (and potentially more than offsetting) the warming effect of greenhouses gases (principally CO2) on the earth. The estimated cost then was several billion dollars a year, a drop in the bucket compared to the trillions of dollars required to essentially replace the fossil-fuel based infrastructure of the global economy. The admitted downside: uncertain effects on ocean life and the food chain of the sulfur dioxide that would be created when the sulfate particles fell to the ocean and mixed with the water there or with rain clouds on their way down.  

My immediate reaction to this presentation is that the world needed a lot more research about this idea, especially how to assess and mitigate the side effects, because the upside was huge. Since I was pessimistic even then that US policymakers, let alone those in other countries – principally China and India -- ever would be able to agree on and implement effective mitigation policies in time to avert potentially future climate-related disasters, some form of geo-engineering, if scientists/innovators could meet the objections, appeared able to solve the climate change problem at a fraction of the cost of the more conventional approaches of reducing or “mitigating” CO2 emissions.

I was reminded of this conference and my reaction then to the geo-engineering presentation last month, when one of the worst and deadliest tornadoes on record tore through a 200-mile path in Arkansas, Kentucky, and Illinois. The event was followed a few days later by hurricane force winds throughout the Midwest (where I live). And all this after a horrendous hurricane season on the Louisiana coast, another summer of devastating wildfires and ongoing drought in the West (which contributed to the Marshall fire in Colorado New Years’ eve), extreme heat in the Northwest and nearby Canada over the summer, and an unprecedented ice storm last winter that brought the whole state of Texas to its knees.

THIS IS NOT NORMAL. Man-made Climate change clearly is here, though it is manifesting itself in highly unpredictable ways, in place and time. This is not to say that climate change clearly was the cause of any of the specific extreme events just listed. No one perfectly understands the “causes” of all weather events as it is. But I understand the consensus of climate experts to be that whatever the underlying probabilities of extreme weather at any point in time and space, climate change increases those probabilities.

More investments in “resilience” or “adaptation” – which I have advocated with my co-author John Fleming – unfortunately cannot solve all climate-related problems. https://www.brookings.edu/research/the-climate-wolf-at-the-door-why-and-how-climate-resilience-should-be-central-to-building-back-better/. There are no resilience measures that can protect against sudden and violent tornadoes. Or against drought. And in the long run, not even against worst case permanent increases in ocean levels of 10 feet or more.

Nor will the conventional wisdom of climate change activists – that the world needs to be far more aggressive about reducing CO2 emissions, or “climate mitigation” – do the trick either. Extreme climate-related or aggravated events, even more intense and more frequent than those recently experienced, are likely to continue and maybe get worse, even if the US and the rest of the world manage to get to “net zero” emissions by the year 2050, an objective that will require huge private and public global investment – in the range of $150 trillion, or about 4-5 percent of global GDP per year, over the next three decades: https://www.bruegel.org/2021/08/how-much-investment-do-we-need-to-reach-net-zero/.  I want to underscore the word “global.” Because the atmosphere, by definition, is global in nature, even if the US were magically able to get to “net zero” quickly, without the rest of the world doing the same (a still distant goal after the latest international climate confab at Glasgow), US efforts will have only a marginal impact on the number and severity of continuing climate-related extreme events.

That is because the earth’s atmosphere is already loaded with greenhouse gases (“carbon” or “CO2” here for short) -- 412 parts per million – a concentration that is 12 percent above the 2000 level, and far above the 350 ppm that was once thought to be “safe.” Indeed, it is officially estimated that the current CO2 concentration in the atmosphere is higher than at any time the last 800,000 years. https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide.

High ambient CO2 concentrations drive climate change, trapping more heat at or near the earth’s surface, thereby distorting the climate while melting ice sheets on the two poles, Greenland, Russia and Scandinavian. Melting raises ocean levels, putting increasing amounts of coastal areas around the world permanently under water.

Even if the rate of new CO2 emissions slows, which it is not even clear that the world is on a path to do, already too high ambient CO2 concentrations will only increase, and so will adverse climate-related impacts from it.

In principle, one way to prevent or mitigate these impacts is through much accelerated rollout of “carbon capture” technologies, which if they worked, would “drain” the climate “bathtub” of existing CO2. I ignore so-called “carbon sequestration and storage,” or technologies that capture CO2 coming out of industrial or electricity-generating smokestacks. CSS is useful but still only keeps newly generated CO2 from going into the atmosphere rather than taking existing CO2 out of it.

One way to reduce ambient CO2 concentration levels is to capture CO2 directly from the atmosphere and then either store it underground or embed it in some useful material like cement. So far direct-air capture (DAC) is very expensive at $600-800/metric ton (or “ton”) – still more than 10 times the cost of mitigating carbon emissions, as one might expect, because so much air must be processed relative to its CO2 content to make a real difference. But one company, Climeworks, has recently put on line a facility in Iceland that aims to get DAC costs down to $100-200 ton, and has found some companies – such as Microsoft, Stripe, Swiss Re – to underwrite the costs of removing some amounts of carbon, and even the band Coldplay, which has engaged the company to cancel out some of the emissions from its upcoming world tour. https://techcrunch.com/2021/12/03/co2-capture-iceland-climeworks-orca/. The US Department of Energy is working to get DAC costs below $100/ton over the next decade. https://www.energy.gov/articles/secretary-granholm-remarks-going-carbon-negative-doe-event-us-pavilion-cop26.

Taking carbon out of the air directly is not the only form of carbon capture. The National Academy of Science released a report last month outlining six possible ways of using the oceans to absorb more CO2, since the more CO2 that can be extracted from seawater, the more carbon the oceans can absorb from the air https://www.nationalacademies.org/news/2021/12/new-report-assesses-the-feasibility-cost-and-potential-impacts-of-ocean-based-carbon-dioxide-removal-approaches-recommends-u-s-research-program. While none of these approaches has yet been commercialized, NAS recommends $125 million in research to turn one or more of the six ideas surveyed in that report into reality. Indeed, one research team at UCLA has reported especially promising results from one technique it has already developed and has plans to pilot test. https://newsroom.ucla.edu/releases/using-seawater-to-reduce-co2-in-atmosphere.

To be economically viable, either or both air or ocean- based carbon capture technologies must be scaled, so that high fixed costs of deployment and R&D can be spread over a larger volume, realizing economies of scale. Accomplishing this, in turn, requires R&D and early-stage proof of concept funding, likely measured in billions of dollars. Once the costs per ton have been brought down to reasonable ranges, say $50-80 ton, substantially greater amounts of funding will be required to finance the deployment of these technologies.

One method for attracting both early and later stage financing for carbon capture is through “advance commitments” whereby the funders, public or private or both, agree to pay for certain amounts of carbon removal. The same funding concept has been used for paying for vaccinations in poor countries: https://www.politico.com/news/agenda/2021/12/22/carbon-removal-advance-market-commitments-525988?fbclid=IwAR1zygcV73sRdnf3wTA46aybwwvhh_eNhFd8aUQW7Qz3Dg71sLwBzuy24Sc.

Carbon removal may be our best bet to avert continuing, and likely more frequent and more severe extreme climate-related weather events, but it will still cost trillions of dollars, depending on the success of CO2 emissions mitigation measures, which as already noted, also will cost trillions (though less if cost-effective capture technologies are in place). And it will take time, likely at least a decade to have a noticeable difference on the climate. There is one key advantage of carbon removal, however: it does not require international agreement. Removing carbon from the air from some locations affects the global atmosphere, and will benefit all (in theory, so much carbon could be removed that the world one day could turn from wrestling with global warming to global cooling, but that day, if it ever comes, is far off).

Which brings me back to geo-engineering, which in principle, should be substantially less expensive and would more immediately offset climate change than either mitigation or removal. In the roughly 15 years since that meeting about geo-engineering I described at the outset, various scientists have proposed other means for enhancing sunlight reflectivity, which may not involve the unknown but potentially dangerous side-effects of spraying sulfate particles into the air. One such idea is to refreeze rapidly warming polar regions by using tall ships to pump salt particles from the ocean into polar clouds to make them brighter. https://www.bbc.com/news/science-environment-48069663.

Another idea reported on PBS earlier this year would paint roughly one percent of the world’s buildings with special white paint, containing barium sulfate, a chemical that is now used to provide contrast in X-rays. This simple technological fix can cool surfaces well below ambient air temperatures – even eliminating the need for air conditioning in some places -- and in that way combat the warming induced by greenhouse gases. https://www.pbs.org/newshour/show/can-the-worlds-whitest-paint-save-the-world.

It mystifies me why more attention hasn’t been paid to the white paint proposal, which at least on the surface (no pun intended), presents little or no downside risks, and huge upsides. Although painting one percent of all structures around the world would be costly, the total costs can’t possibly be anything like the trillions of dollars annually for effective mitigation or carbon capture. Maybe there are supply constraints on the production of barium sulfate, but assuming there aren’t, it would pay for the US to subsidize the deployment of this simple white paint solution throughout the world, with funds funneled through an international organization like the World Bank. If the US government doesn’t want to pay, then the advanced commitment of private sector dollars now going into or contemplated for carbon removal could be used to pay for the white paint solution. And with no apparent side-effects, this approach would not present the kinds of global coordination problems that have plagued repeated global climate change conferences about mitigation and carbon removal, or other solutions that rely on sunlight reflection rather than emissions mitigation. Indeed, developing countries that are least equipped to make the transition to green energy, may provide the largest constituency for climate measures that rely more on enhancing reflectivity than mitigation/capture.

But there is one drawback to any of the reflection-based solutions to climate change discussed here, even as interest in them grows among climate scientists: the closer they get to implementation the more they are likely to deter investments in other climate change measures, not just mitigation but also carbon removal, which we may still need if the reflection-based approaches don’t pan out. https://e360.yale.edu/features/geoengineer-the-planet-more-scientists-now-say-it-must-be-an-option. Moreover, some climate activists will criticize any solution that allows the continued use of fossil fuels as somehow immoral or dangerous.

In my mind, and perhaps yours, our collective eyes should be on the right ball: getting control of climate change as rapidly and as cost-effectively as possible, with a minimum of known and unintended downsides. If that means that some technologies now on the drawing boards fall by the wayside, so be it. If that means the world can continue to use fossil fuels, safely, for decades more, that’s fine too, so long as doing so doesn’t destroy the planet.

In sum, more serious attention should be given by policy makers and all those in the private sector eager to address climate change to ideas that once seemed to fringe or even crazy, but in fact might offer the climate breakthrough the world needs, and soon.