Fourteen years ago, on this day, July 11st, 2012,
2012 excellent (imo – ymmv) piece on complexity of food productivity by Homer Dixon is published.
In the mid-1980s, when I was a doctoral student at the Massachusetts Institute of Technology and beginning to study climate change, I attended a lecture by a specialist in plant physiology at nearby Harvard University. He spoke about global warming’s impact on crop productivity. He was quite optimistic. More carbon dioxide in the air, he explained, causes certain kinds of plants to grow faster. So, on balance, food output should rise in a warmer and CO2-rich world.
I chased him down after the lecture and pressed him on things that could make plant response more complex. If plants absorb more CO2, I asked, won’t that change the nitrogen-carbon balance in their tissues and make them less nutritious? And what about other factors that might change in a warmer world, such as soil moisture and the distribution of weeds and pests – shouldn’t we take them into account, too?
He agreed that the issue was more complex than he’d suggested. “But we don’t have good data on these other factors yet,” he said, “so I didn’t talk about them.”
Almost three decades later, we have vastly more data, and the picture is far less rosy. We’ve learned that in the real world, unlike in experimental plots that control everything except ambient CO2 concentration, factors like drier soil and worse pest infestations can swamp carbon dioxide’s positive effect. And one thing that didn’t figure much in experts’ analysis in those days, and which I didn’t ask the Harvard speaker about, turns out to be a really big deal: heat shock.
The amount of carbon dioxide in the air was 395ppm. As of 2026, when this post was published, it is 430ppm. This matters because the more carbon dioxide in the air, the more heat gets trapped. The more heat, the more extreme weather events. You can make it more complicated than that if you want, but really, it’s not. Fwiw, I have a tattoo of the Keeling Curve on my left forearm.
The broader context was that biologists have known about carbon dioxide build-up as an issue since the 1940s (see Evelyn Hutchinson, of Yale, for example). From the mid-1960s, word was spreading. (It’s important not to restrict understanding of what was known about climate change to meteorologists and climatologists!)
The specific context was that Homer Dixon has written books that I think raise important questions and give useful (which is not automatically to say correct) answers.
What I think we can learn from this – in the 1980s, carbon dioxide build-up was not a contested topic in many circles. People just got on with thinking what the implications would be building on work of people like Stephen Schneider, Robert Schware, Bert Bolin, William Kellogg etc etc.
What happened next – it all got politicised by the fossil fuel lobby in the late 1980s, for entirely predictable and cynical reasons.
On this topic, you might like these other posts on All Our Yesterdays
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You can see the chronological list of All Our Yesterdays “on this day” posts here.
What do you think? Does this pass the ‘so what?’ threshold? Have I got facts wrong? Interpretation wrong? Please do comment on this post, unless you are a denialist, obvs.
If you want to get involved, let me know.
If you want to invite me on your podcast, that would boost my ego and probably improve the currently pitiful hit-rate on this site (the two are not-unrelated).
Also on this day:
July 24, 1977 – Climate change as red light? “No, but flashing yellow.”
July 24, 1980 – “Global 2000” report released.
July 24, 2001 – Running from the Storm? Nah, we’re slouching towards it
July 24, 2011 – Rubbery numbers about Gillard’s carbon pricing proposal are disputed…
