Geoengineering Now!

Author: Maxwell Tabarrok

Jan 02, 2024

Maxwell Tabarrok is an economics researcher at Dartmouth College and the author of the Maximum Progress substack. Maximum Progress is a blog about the economics, history, science, philosophy, and culture surrounding a single graph: World GDP Over the Last Two Millennia, The Great Fact, The Hockey Stick, The Arc of Human History.

If you took a globe-trotting trip from the Historic Pleasure Pier of Galveston, Texas, to the Italian Bridge over the Tigris in Basra, Iraq, to the Grand Masonic Temple in Monrovia, Liberia, you’d find little in common between your destinations. But if you took this same trip 100 years from now, each place might look exactly the same: wide open ocean.

This is the promise of even relatively mild climate projections of temperature rise and melting sea ice. For these reasons and more, temperature rise is worth avoiding or at least controlling, but many of the proposed solutions to temperature rise, e.g rapidly ending the use of fossil fuels, seem untenable.

Massive economic sacrifices are not the only way to avoid global warming though. Solar geoengineering can offset every degree of anthropogenic temperature rise for single-digit billions of dollars. Perhaps for less than what Italy spends on Venice’s flood walls alone.

Here’s the science and economics of how solar geoengineering works.

The simplest view of the Earth's temperature is like a diet: calories in, calories out. The calories coming in are rays of light from the sun, and instead of coming out through exercise, they go out as reflections radiated into space. Most forms of solar geoengineering work by making the Earth more reflective. The type we’ll focus on in this post uses sulfur dioxide, pumped high into the stratosphere, which quickly binds with water molecules making them bright white sulfuric acid, reflecting lots of light back out into space.

There is an intuitive way to prove the potential of geoengineering to those of us without expertise in climate chemistry: a natural experiment. Consider the eruption of Mount Pinatubo in 1991, the second largest volcanic eruption of the 20th century. Its massive belch of volcanic ash is the perfect source of random variation in the sulfur dioxide content of the atmosphere. Here’s what happened to global average temperatures after the eruption:

This graph alone isn’t enough to quantify the exact temperature impact of Pinatubo’s 20 million tons of sulfur output. You need fine-tuned climate models and lots more data to compare the observations to the counterfactual temperature if Pinatubo had not erupted. When climate scientists do this they come to a global average cooling effect of about 1°F.

But as Charles C. Mann puts it

The cooling from Pinatubo’s 20 million tons of sulfur dioxide was geophysical happenstance; the droplets it formed were not of the optimal size. By making smaller, more effective droplets, geoengineers could achieve the same reduction by spraying just a few million tons of sulfur dioxide into the air in a year. Actually, they would probably spray sulfuric acid directly, rather than having the atmosphere convert sulfur dioxide, but the principle is the same.

Sulfuric acid is perhaps the single most important industrial chemical, global yearly production is around 180 million tons, so supply in large quantities would not be a challenge economically or logistically.

After sourcing the chemicals, you need a way to loft them high into the stratosphere. This would not be particularly expensive either. This analysis predicts that a quarter million tons of sulfur dioxide would halve the rate of temperature increase for around 2.25 billion dollars a year, including the cost of chemicals and the airplanes to disperse them.

That is astoundingly cheap. It’s difficult to contextualize numbers like this so here are some comparisons: $2.25 billion is .008% of yearly US GDP, it’s a little less than the GDP of Bhutan. It’s about 5 times less than the market cap of the regional rust-belt financial institution, KeyBank, and almost exactly what the US Forest Service spends on wildland fire management each year.

There are known side effects to sulfur geoengineering such as ozone damage, but these can be mitigated for costs that still keep the overall cost of the effort astoundingly low compared to the benefits it produces by delaying and mitigating the damages of climate change.

There is extensive scientific debate over the exact mechanisms and feedback effects that would arise from solar geoengineering of this kind, far more than I can do justice in this blog post. But the basic facts are undisputed: solar geoengineering on the scale required to completely offset anthropogenic warming is easily within the technical and economic feasibility of any developed nation and is often far cheaper than the current climate mitigation strategies employed by these nations.

Here are the arguments against solar geoengineering

The claim that there is something like a silver bullet for climate change just sitting around without anyone using it rightly stretches belief too far for some. But for those of us familiar with government’s self-mutilating habits around nuclear power, environmental permitting, and medical regulation all around the world, it might be more believable.

Still, it would be foolish to ignore the arguments against solar geoengineering.

The most popular one is moral hazard. This argument claims that if we use solar geoengineering to mitigate the negative impacts of carbon emissions, then people will be less willing to curb their emissions and we’ll end up with more environmental damage. There are a couple of problems with this argument.

First is that moral hazard does not apply to externalities like carbon emissions. The central problem of climate change is that the cost of emitting an extra ton of carbon is not paid by the person who does it. So coal plants mine and burn too much coal because they can ignore the cost that carbon emissions impose on the rest of the world and the future. Read that again: the central problem of climate change is that decision makers ignore the costs of carbon emissions. Since these costs are already ignored by energy companies and governments, decreasing them will not change their actions, but they will save the world from trillions of dollars worth of death and environmental damage.

Second, the costs of carbon emissions are not needed to motivate a transition to clean energy. Solar plants with large battery storage capacity are cheap even without subsidies, and more than half of new power generation in the US is solar power. Solar power will win, it just needs time and permitting reform. Geoengineering can provide the time that solar power needs to take over energy production all around the world.

The other arguments against geoengineering focus on possibly unpredictable and unequal effects. The global average temperature decrease can be confidently predicted, but the fractally complex climate system would change wind, weather, precipitation, and temperature patterns in different ways all around the world.

This is surely true about geoengineering but it is also true about all of our paths forward. Human carbon emissions have already massively changed the atmospheric chemistry of the earth. If we try to reverse this massive change with carbon removal or by cutting emissions, the Earth’s climate chemistry will undergo a massive reversal with unpredictable and unequal butterfly effects all around the world.

Some places will get hotter, others will get cooler. Different places will gain and lose agricultural productivity. Some environments will be preserved and others will collapse in response to the changes in atmospheric carbon content. There is no path forward without rippling butterfly effects on the climate. Solar geoengineering solves the immediate problem of temperature rise cheaply enough that tens of billions of dollars can be set aside to address unequal or unforeseen side effects and still be affordable.

There are several ways to keep Galveston, Basra, and Monrovia above sea level. Extensive sea walls, carbon capture, cutting emissions, or solar geoengineering. Of all the possible solutions, solar geoengineering is the cheapest, fastest, and most complete. Its main drawbacks are shared with the most popular plans to address climate change and it has huge advantages that no other solution can match.

Let’s not wait too long or pay too much to avoid the damages of climate change! Geoengineering now!