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  • Writer's pictureAllan Dyen-Shapiro

Things are worse than assumed: sensible numbers on carbon fluxes from soil and limits of discourse

Imagine you are appointed to a committee of wizards, meeting in some dingy (and likely dragon-infested) back room in Hogwarts, tasked with convincing Muggles to take sensible action on climate change. Being a cup half-full type of wizard (because you know the spell that leaves your cup exactly half-full), you take comfort in the idea that Voldemort, who despises Muggles, would never choose to double the size of the United States.

Well, soil scientist just did precisely this with a paper published in Nature this week, at least as far as American impact on climate change. For once, the newspaper headlines got it right: a 12-17% increase in the amount of global carbon emission over the next thirty-five years is precisely what the soundbite said it was, equivalent to adding another United States to the world. Predictably, the Vernon Dursleys will rail about those left-wing scientists whose models are all just playing with computers and who just want to sponge off the hard work of captains of industry, families of good name, the Malfoys of the world. In reality, the contribution of carbon emitted from the soil had been purposely neglected in models created by the IPCC and others because no good numbers were available, and they wanted estimates to be conservative as possible.

Now there are reliable numbers. What Crowther et al did (Go to Facebook using the link on this page and friend me, and I will post the .pdf file of this article, obtained thanks to the Kazakhstani fighters for information freedom at Sci-Hub--and I'm serious about my praise for these folks; check out my previous blog post on Sci-Hub here: . Note that the domain name for Sci-Hub is now changed to .cc because of legal action.) was to compare the results of 49 studies of soil carbon flux performed all over the world in a variety of climates. Basic protocol: take some land, heat part of it, and measure carbon flux in both parts.

There's a really cool figure that uses a statistical technique called bootstrapping (re-running analysis with only part of the data to see if you still get the same overall results; if you do, you say the model has high bootstrap support, and you are confident the conclusions are statistically sound) to show that using a lot of studies vastly increased the correspondence between measured carbon flux and model-predicted carbon flux. You rarely see something like this--a meta-analysis that proved that only by doing a meta-analysis could you make sense of very complicated data.

Here's the high school science version of the concepts: photosynthesis takes carbon out of the atmosphere and makes plants; respiration by all organisms uses that carbon for energy and releases carbon back to the atmosphere as carbon dioxide. The photosynthesis to respiration (P:R) ratio says whether an ecosystem is increasing its carbon stores or releasing carbon. If the ratio is greater than one, the ecosystem is accumulating carbon; if less than one, it's releasing it.

The more carbon already in the ground as dead organic material and live bacteria and fungi, the more capacity there is for respiration. Most chemical reactions go faster at higher temperatures, and it was known that the rates of both sequestering and releasing carbon increased with temperature. The balance between the two was not previously known. It is now known that carbon flux depends on only one major variable: the more carbon in the ground, the more net release of carbon dioxide as temperature rises. The other environmental variables examined--precipitation, soil pH, soil type, mean annual temperature--made no statistically significant differences in the results.

The authors then used this relationship to look at the entire planet with its varying climates and soil types and predict what will happen by the year 2050, giving the bad news with which I started this blog post. We will see positive feedback: some warming leads to more soil carbon release leads to more warming. The paper can't tell us exact numbers. Indeed, a table is included spelling out every uncertainty in the measurements (and what future research is needed to resolve those uncertainties), but the new is bad.

I read this paper while sitting in the waiting room of Tire Choice, while mechanics worked on my old Corolla. (No, not a new Prius; because with the environmental cost of making new aluminum and making batteries with a five-year lifespan, keeping an old car in good working order is the most environmentally friendly option at present.) FOX News was on. A story came on about a college campus in which the president had received threats because he lowered the American flag when Trump was elected. I looked up only because my son is applying to this college. Next to me was an old man who railed out loud about the damn liberals who were ruining this country and asked me what we should do with Commie bastards like that university president and what prison was best for housing all the Hillary Clinton voters.

I might have ignored the guy, but as he refused to disengage, I decided to try to educate instead. Turns out the guy wasn't nearly as dumb as he sounded. He had been born very poor, worked his way through college to become a chemical engineer, built a multimillion dollar company, sold it, and was living a very comfortable retirement. When he got around to global climate change (apparently a favorite topic of his), I disarmed him. I asked if he had read the literature. He said no, but there were five hundred scientists who said... I interrupted. Your information is outdated, I said. Based on an analysis of peer reviewed papers, 99.99% of climate scientists agree with the consensus that global warming is primarily caused by human activity. I'll bet they're all biased, he railed, and don't you think we should look at both sides of the debate? I responded that science is not a debate. Opinions don't matter. Data matters, and the methods by which that data was obtained matter. If either are faulty, if the experiments are important, they will be repeated. Again I asked why he hadn't read the literature himself, as he said he could.

Well, I'm in retirement, worried more about my golf game, he said. Do you have children or grandchildren? I asked. He did. Then why are you voting without a full understanding that you are completely capable of obtaining about the key issue of their generation? Why are you choosing ignorance? Why don't you read the literature and not trust whomever the TV chooses to quote?

It stumped him. He had no answer, so he did what ideologues do: he changed the subject. It's all about population, he said. This world isn't build for 7 billion.

I disarmed him again by agreeing. I cited data about how birth rates decline to levels comparable to the US when there are high levels of education for girls, economic opportunities for women, and access to affordable/safe/reliable birth control. He said that would never work in India because of religion. I informed him that Hindus had no opposition to either birth control or abortion. He then asked what about the Muslims. I cited statistics from Muslim countries that followed the same general trends I had outlined.

He pondered. He had no answer.

Importantly, a dozen others were listening.

The take-home point is that although Muggles can be quite blind, our kids' generation is in deep trouble unless the "conventional wisdom" is challenged, openly, on a daily basis. I'm going to continue in this blog to try to bridge the gap between what the media reports and what the scientific literature offers, for the benefit of those who don't have the freedom in their lives to dedicate the time it would take them to learn how to read the scientific literature. Here's the deal: those reading need to continue to engage those who would eliminate our kids' future.

As alone as many of us sometimes feel, we must keep using that cup half-full spell, because there is no real alternative.

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