As I catch up with social media posts and their need for soundbite-sized summaries, I thought I’d distill the past 17 issues in a way that can be written as a single article.

The problem has been summarized several times in earlier installments, but it bears repeating since half of any solution involves a crystal clear problem statement. Here it is:

• The increase in carbon dioxide levels in the atmosphere, attributable to human extraction and combustion of geologic carbon over 350 years of industrialization, threatens to destabilize Earth’s climates.

A couple of notable features of this carefully worded statement: Carbon dioxide, not any other “greenhouse gas,” is the most significant threat and must be addressed. Humans are worsening the problem by continuing to dig stuff out of the ground and burn it, but we’ve been doing that for generations. While we should minimize this activity, it’s part of the fabric of modern human society.

Further, while “climate change” (or perhaps “the climate crisis”) is front and center on the news, it actually hasn’t happened yet, and when it happens, we have no clear view of the result.

Question: If we stop our emissions, won’t that solve the problem?

Answer: No. Even if we went cold turkey, carbon dioxide would persist for far too long for Earth to stabilize. So, we must actively reverse the process by taking carbon dioxide out of the atmosphere.

Question: OK. So if we have to take it out of the atmosphere, can’t we create a big machine to clean it up?

Answer: It’s not that simple. Taking carbon dioxide out of the atmosphere requires energy, which has a cost (currently, the energy necessary adds more carbon dioxide to the atmosphere than it removes overall). Imagine all the machines we have created that put carbon dioxide into the atmosphere! Removal machinery would need to be about that big just to remove what we’re putting out. The scale is a huge problem; without going to scale, it only slows the inevitable.

A more significant problem is economic: The only way “direct air capture” engineering makes sense without a product in mind is with subsidies—if there’s no product, someone has to pay. The popular solution, artificial carbon markets, can’t scale enough to change our atmosphere: They are political fig leaves that provide false hope.

Question: Ah. So, you’re just a doom-monger telling us that we’re unavoidably screwed because of our past activities, right?

Answer: Well, no. I’m a scientist, perhaps a “public intellectual” wannabe, an old-school idealist who believes that problems, once defined, can be solved by careful and rigorous thinking, followed by purposeful action. If we unnecessarily complicate the situation, our current activities will be unduly complicated and fail to lead to a solution.

Question: OK, Mr. “Public Intellectual”, there are a lot of scientists and engineers working on this problem! What makes you think you have an answer?

Answer: Well, scientists and engineers (including myself) are trained to solve puzzles without considering economics. But carbon removal isn’t a challenge from a technology perspective—many solutions exist. These solutions gloss over the genuine economic burden such technologies would require if implemented at the necessary scale. Those “working on the problem” are working on the wrong ones.

I think I have an answer because I’ve defined the problem carefully and considered the specific economic limitations. Solutions other than agriculture fail the “Is it ever profitable without subsidies?” or the “Can it scale enough to make a difference?” tests.

There’s also a further lesson, a sort of self-realization: When I visualized a path toward a workable solution, it closed my eyes to implicit assumptions that should have been challenged and expanded upon before jumping to a conclusion. Specifically, once I visualized the amount of carbon-free energy needed to scale desalination cheaply, my mind narrowed to “nuclear” as the only solution. It turns out it’s not.

I suspect I’m not the only one with intellectual tunnel vision, and this propensity became more apparent after listening to the Freakonomics Radio installment I linked to last time.