Engineering a way out of global warming

After its licentious article about Earth having a second moon, I thought National Geographic had published another subpar piece when I saw this headline:

Small Nuclear War Could Reverse Global Warming for Years

The headline is click-bait. The article itself is about how regional nuclear war, such as between two countries like India and Pakistan, can have global consequences, especially on the climate and agriculture. That it wouldn’t take World War III + nuclear winter for the entire world to suffer the consequences of a few – not hundreds of – nuclear explosions. And that we shouldn’t labour with the presumption that detonating a few nuclear bombs would be better than having to set all of them off. So I wouldn’t have used that headline – which seems to suggest we should maybe implanting the atmosphere with thousands of tonnes of some material to cool the planet down.

I don’t think it’s silly to come to that conclusion. Scientists at the oh-so-exalted Harvard and Yale Universities are suggesting something similar: injecting the stratosphere with an aerosol to absorb heat and cool Earth’s surface. Suddenly, global warming isn’t our biggest problem, these guys are. Through a paper published in the journal Environmental Research Letters, they say that it would be both feasible and affordable to “cut the rate of global warming in half” (source: CNN) using this method. From their paper:

Total pre-start costs to launch a hypothetical SAI effort 15 years from now are ~$3.5 billion in 2018 US $. A program that would deploy 0.2 Mt of SO2 in year 1 and ramp up linearly thereafter at 0.2 Mt SO2/yr would require average annual operating costs of ~$2.25 billion/yr over 15 years. While these figures include all development and direct operating costs, they do not include any indirect costs such as for monitoring and measuring the impacts of SAI deployment, leading Reynolds et al (2016) to call SAI’s low costs a solar geoengineering ‘trope’ that has ‘overstayed its welcome’. Estimating such numbers is highly speculative. Keith et al (2017), among others, simply takes the entire US Global Change Research Program budget of $3 billion/yr as a rough proxy (Our Changing Planet 2016), more than doubling our average annual deployment estimates.


Whether the annual number is $2.25 or $5.25 billion to cut average projected increases in radiative forcing in half from a particular date onward, these numbers confirm prior low estimates that invoke the ‘incredible economics’ of solar geoengineering (Barrett 2008) and descriptions of its ‘free driver’ properties (Wagner and Weitzman 2012, 2015, Weitzman 2015).

My problem isn’t that these guys undertook their study. Scientifically devised methods to engineering the soil and air to slow or disrupt global warming have been around for many decades (including using a “space-based solar shield”). The present study simply evaluated one idea to find that it is eminently possible and that it could deliver a more than acceptable return per dollar spent (notwithstanding the comment on unreliable speculation and its consequences). Heck, the scientists even add:

Dozens of countries would have both the expertise and the money to launch such a program. Around 50 countries have military budgets greater than $3 billion, with 30 greater than $6 billion.

I’m all for blue-sky research – even if this particular analysis may not qualify in that category – and that knowing something is an end in and of itself. I.e., knowledge cannot be useless because knowing has value. Second: I don’t think any government or organisation is going to be able to implement a regional, leave alone global, SAI programme just because this paper has found that it is a workable idea. Then again, ability is not the same as consideration and consideration has its consequences as well.

My grouse is with a few lines in the paper’s ‘Conclusion’, where the scientists state that they “make no judgment about the desirability of [stratospheric aerosol injection].” They go on to state that their work is solely from an “engineering perspective” – as if to suggest that should anyone seriously consider implementing SAI, their paper is happy to provide the requisite support.

However, the scientists should have passed judgment about the desirability of SAI instead of copping out. I can’t understand why they chose to do so; it is the easiest conclusion in the whole enterprise. No policymaker or lawmaker who thinks anthropogenic global warming (AGW) is real is going to consider this method to deal with the problem (or maybe they will, who knows; the Delhi government thinks it’s responding right by installing giant air filters in public spaces). As David Archer, a geophysicist at the University of Chicago, told CNN:

It will be tempting to continue to procrastinate on cleaning up our energy system, but we’d be leaving the planet on a form of life-support. If a future generation failed to pay their climate bill they would get all of our warming all at once.

By not judging the “desirability of SAI”, the scientists have effectively abdicated their responsibility to properly qualify the nature and value of their work, and situate it in its wider political context. They have left the door open to harmful use of their work as well. Consider the difference between a lawmaker brandishing a journal article that simply lays out the “engineering perspective” and another having to deal with an article that discusses the engineering as well as the desirability vis-à-vis the nature and scope of AGW.