The Case for Geoengineering: Solar Radiation Modification as a Necessary Climate Solution

Welcome to the twenty-one new subscribers who have joined Unearthed since the last post! Today, we have a doozy lined up: Geoengineering.

Geoengineering entails the intentional modification of earth’s climate for human purposes, such as stopping global warming or preventing an ice age. But, dear reader, this is not a topic for polite cocktail party chatter, because an intentional intervention into the Earth’s climate is seen as highly controversial, especially within environmental circles. So why are top scientists from institutions like Harvard, MIT, and Columbia publicly arguing for more research into the topic?

After a canny rebranding as “solar radiation modification”, the case for geoengineering goes like this:

1. Meeting Net Zero goals like the Paris Agreement will entail tremendous cost and economic sacrifice. The requirements for electrification alone look Sisyphean: how will we possibly be able to double world copper supply in the next 10-15 years? What about cobalt, or lithium?

2. Even if we do meet our goals for electrification, we will struggle to meet Net Zero because of the challenge of carbon dioxide removal. This is required to offset certain sectors like international air travel for which there is no plausible alternative. We simply do not have the technology to deliver the needed offsets at scale, at cost.

3. Even if we did manage to hit those targets, with carbon dioxide removal at scale, we still face significant risks for passing certain “tipping points” like the destabilization of the Greenland Ice Sheet, melting permafrost, or changes in North Atlantic ocean circulation.

4. So what do we do? We can buy ourselves time, cheaply and at scale, by mitigating solar radiation through natural solutions like stratospheric aerosols or cloud brightening.¹

Solar radiation management is one of those things that provokes guttural reactions in folks, so I would ask for your patience as I walk through the above arguments.

The Challenges of Achieving Net Zero Goals

Can we even achieve Net Zero by 2050 if we try? The IMF has identified mining capacity as a tremendous challenge to climate goals, with the soaring demand required to electrify everything likely leading to price spikes for critical materials. As Daniel Yergin² writes in the WSJ,

…translating the 2050 net zero goals into the equipment and technologies that will be needed—electric-vehicle batteries and charging stations, offshore wind, onshore wind, solar panels, battery storage, etc.—adds up to a doubling of the need for copper by the mid-2030s.

Doubling copper production is no easy task, especially not by the mid-2030s. Copper mines can take 15-20 years to develop. Current copper production is dominated by Chile, Peru, China, and the Congo. With the current political instability in Chile and Peru, our existing copper supply isn’t certain, to say nothing of unprecedented growth.

Even in stable, business-friendly countries like Australia, the US, and Mexico, passing the permitting process and securing agreements from local stakeholders has become harder and harder for major new mining projects.

Beyond the copper production issue, there are also major questions about production of lithium, cobalt, and rare earths. The processing supply chains for these minerals often go through China, even if the resource itself is produced elsewhere.

Carbon Dioxide Removal

Transitioning to renewables and electric vehicles is only one part of achieving Net Zero by 2050. We also have to scale up Carbon Dioxide Removal.

I’ll let Prof. David T. Ho explain from his recent Nature article:

Carbon dioxide removal (CDR) is what puts the ‘net’ into ‘net zero emissions’. All pathways to limit global warming to 1.5–2 °C above pre-industrial levels that have been assessed by the Intergovernmental Panel on Climate Change require rapid decarbonization to start now. But they also require the removal of CO₂ from the atmosphere because we won’t be able to eliminate carbon emissions entirely on the required time scales. ‘Hard to abate’ sectors such as aviation and shipping will remain large sources of greenhouse gases even in the most optimistic scenarios.

The Biden administration’s planned Direct Air Capture (DAC) hubs are expected to be able to remove a million tons of CO₂ a year—each. While that sounds like a staggeringly large number (I mean, it is pretty impressive), it’s only a drop in the bucket against the 40.5 billion tons emitted in 2022. So each DAC hub would offset 13 minutes of global emissions, meaning we would need over 40,000 to offset 2022. At just under a billion dollars each…. that’s quite the expense.

Now, of course we can expect dramatic cost improvements through time. But Professor Ho, a specialist in carbon capture and the carbon cycle, argues that we simply will not be able to build these fast enough to meet net zero goals. His conclusion is thus that we need to decarbonize faster, though another clear line of thought is that we need other, cheaper, more scalable methods for offsetting warming.

Climate Change Tipping Points

Let’s pretend for a minute that we do manage to hit Net Zero by 2050. We won’t get crushed by climate change, right? …. right??

The Earth’s climate is an incredibly chaotic, difficult-to-model system, in part thanks to feedback loops. I remember learning about the bewildering complexity of these in my undergraduate paleoclimatology class. For example: the planet warms, so glaciers and ice sheets melt. This exposes bare rock or water, which are both more absorptive of sunlight than ice, so the planet warms more. The reverse is also true: ice buildups make the earth more reflective, which further cools it. There are many such feedback loops, both positive (which accelerate change) and negative (which slow change).

Much of the risk of climate change is not simply in higher temperatures, but in triggering a catastrophic feedback loop after passing some tipping point. Following our above example, if the Greenland Ice melts, we would face further warming, plus 23+ feet of global sea level rise.

A paper in Science from last fall argues that even hitting Net Zero goals to keep warming to 1.5-2°C still carries significant risk of hitting global tipping points³. Here is the key graphic. The bar charts show modeled risk envelopes for different tipping points. The green line shows 2°C warming (which is not even the upper end of Paris targets). Note that that line is above the likely tipping point for multiple tipping elements.

McKay et al., 2022. Exceeding 1.5°C global warming could trigger multiple climate tipping points. Science.

This gets us to the most persuasive argument for solar radiation management: even if we manage to limit warming to 2°C, we may still face catastrophe.

The case for Solar Radiation Modification

If we are unable to stop sufficient warming with energy transition or carbon dioxide removal, we can still offset warming with other methods, chiefly by making the earth’s atmosphere more reflective to incoming solar radiation. Over 100 brave scientists have published a letter arguing for more research into just how we might accomplish that. The list includes distinguished professors from the atmospheric sciences, physics, oceanic studies, and geosciences across the globe, at institutions including MIT, Harvard, Columbia, the University of Washington, Oxford, the Sorbonne, and IIS — to name a few.

Their argument follows these simple points:

• The world will continue to warm even if we were to stop emissions today, due to the delayed response between CO₂ and warming.

• Existing aerosol emissions already offset CO₂ warming, and we have high confidence in their ability to do so at scale, even if we need to do a lot more research about how to do that in practice.

• We will not be able to get carbon dioxide removal to scale in time.

• Solar radiation modification, such as stratospheric aerosol injection, would likely be incredibly effective and scalable.

• Because of the efficacy of SDRs, we need to research them, today, because of their potential impacts, globally and locally.

I will add something that the authors don’t mention: stratospheric aerosol injection would be cheap. Really, really cheap—at least compared to other methods of reducing warming. Why would it be cheap? You just put some sulfates into airplanes or rockets or balloons, and launch them into the stratosphere. That’s it!!! Essentially, you mimic the natural cooling effect of volcanic eruptions, which are well-studied and well-known. And the effects are reversible — the aerosols slowly fall out of the atmosphere.

We need more research, but let’s take one ballpark figure from a Harvard study: $18 billion a year to offset each degree of warming. Yes, you read that correctly! Compare that to the Inflation Reduction Act, which will rack up between $500 billion and $1.2 trillion, and is far from all the expenditure needed to stop warming.

Even if you are skeptical, solar radiation management can buy us time: time to electrify, time to develop supply chains, time to develop new nuclear technologies. Furthermore, the cost of sulfate aerosol injection is so low that individual countries may find the cost-benefit analysis in their favor. Would Bangladesh or another low-lying country find it a worthwhile investment to reduce their flooding risk? We need research and global coordination on this subject.

The radical middle

As I have thought through geoengineering over the years, I have never been able to shake this simple conclusion:

The larger the risk of climate change, the stronger the argument for geoengineering.

The corollary follows: the more you believe in the risks of climate change, the stronger you should be arguing for geoengineering.

Even setting aside cost-benefit arguments, which are overwhelmingly tilted in favor of solar radiation management, you will arrive at that conclusion if you acknowledge the latent warming baked into our current CO₂ levels and the impossibility of immediately reversing our emissions.

So why isn’t there more research into geoengineering, let alone action?

The biggest arguments against geoengineering include the risk of changing weather patterns or other unknown consequences. Indeed, we should expect some minor changes, but compare these to the catastrophic risks of continued warming. If anything, this is an argument for more research!

I think the resistance to geoengineering mostly comes not from a rigorous risk-cost-benefit analysis, but instead something deeper. For some, taking action on climate change is deeply convolved with action on other topics, like fighting capitalism, colonialism, or inequality⁴. Other groups are mentally (or even spiritually) invested in the idea of the imminent apocalypse, from which only radical sacrifice can deliver us. And of course, many groups stand to benefit from action on decarbonization, including financiers, governments, and multinational corporations. It’s the classic “baptists and bootleggers” combination — true believers allied with opportunists⁵. For these groups, the possibility that climate change could be mitigated cheaply and effectively represents an existential risk.

I have to applaud the scientists for signing their Solar Radiation Modification Action Letter. Beyond taking on the unholy baptists and bootleggers alliance, these scientists are also facing the taboo against intentional modification of the climate.

Solar radiation modification simply must be discussed. We have modified the climate for thousands of years, through agriculture, grazing, and city-building. We have burned wood, grasslands, peat, coal, gas, and oil. We have released various chemicals, intentionally or not, that have altered our atmosphere and ozone layer. Compared to all those actions, temporarily putting a small amount of sulfate aerosols into the atmosphere, mimicking common volcanic eruptions, is natural, effective, and sensible.

I hope you have found this post informative, at a minimum. If you can, please give it a like, a comment, or share with someone you think needs to hear about it. It will help others learn about this critical subject.

1. Of course, there are other thing we can do, though my focus here is on geoengineering. We can build our resiliency to climate change and extreme events with improved global wealth and robust infrastructure. We could increase investment in new technologies for energy production. We could accept increased risk levels as less costly than the alternatives. We could deindustrialize and reduce living standards. Personally, I am in the camp of technology, resiliency, and probably some geoengineering.

2. Vice-chair of S&P Global and generally renowned energy expert and economic historian. Also author of The Prize, which is required reading for anyone in the oil industry.

3. This presentation has been receiving a lot of attention recently thanks to a presentation at Davos and the associated social media push. I recommend looking at this video, which is a little doomery for me, but gives you an idea: https://www.linkedin.com/posts/world-economic-forum_wef23-activity-7055420048441516032-GbFU?utm_source=share&utm_medium=member_desktop

Note: be wary of any presentation with a scary map!!

4. For the pessimistic version, take the recent Harper’s Magazine article, Apocalypse Nowish. Key quote: “We could build a free society that doesn’t view the planet as a profit engine. I just really doubt that we will. Climate disaster, economic collapse, war, resurgent fascism and nationalism, assaults on basic political freedoms, mass violence: all these mutually reinforcing in a sinister feedback loop, the structural stresses of capital’s death throes accelerating ecological catastrophe and exacerbating reactionary forces, which in turn further stress the structure.” Oof.

5. For more, see the 2022 Unearthed Book of the Year, Where is My Flying Car, by J. Storrs Hall