Deciphering the carbon cycle to reduce global warming

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Photo by Martin Snicer. (Source: Flickr)

Among the many things that have to be done to fight global warming, the #1 issue is to decrease the amount of carbon we’re adding to our planet’s atmosphere as greenhouse effect gases, primarily methane and carbon dioxide. But being efficient in doing that requires understanding the carbon cycle.

(Side note: let’s all please refrain from using the expression “climate change”, which was only invented to make the whole thing sound a lot less scary than it actually is. The truth of what we’re facing is global warming — yes, even if you reckon last winter was really cold).

Carbon dioxide is carbon with oxygen, and methane is carbon with hydrogen. So it’s pretty plain to see that the source of the problem is carbon. The thing is, getting familiar with the concept of the carbon cycle is essential to really understand what needs to be done stop the vicious cycle of increasing global temperatures, but it’s much trickier to grasp than a striking image like melting icecaps or centennial droughts.

Getting intensity and additionality

Carbon is everywhere around us: trees, food, rocks: they’re all carbon — even our own bodies are nearly one-fifth carbon — and then of course there’s coal, oil and gas. The problem isn’t how much carbon there is, but what role it’s playing in the biosphere. Translating this to the question of the man-made emissions causing global warming, which essentially consist in shifting carbon from one location to another, the question isn’t so much what type of energy you’re using or even how much — though those obviously remain important factors — it’s about how much carbon you’re consuming when you use that energy, and most importantly, where you’re taking that carbon from. So there are two questions here: carbon intensity and carbon additionality.

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Carbon is everywhere, even in our bodies

The tricky thing is that even zero-emission energies like electricity can be carbon intensive. In fact, an argument sometimes made against electric cars, for example, is that they hardly solve the problem of emissions because nearly 40% of the planet’s electricity is unfortunately still produced by coal power plants.

That being said, you could perfectly well produce enough electricity to power all the electric cars in the world without using any fossil fuels at all. It’s just a matter of building the right infrastructure (which is being done right now — just not fast enough). When you do that, you decrease or even erase the carbon intensity of electric mobility. And of course the same goes for every sector, every type of energy consumption.

What you can’t do on the other hand is power engines that only run on oil-based fuel without injecting carbon into the atmosphere in the process. Doing things one step better would be powering those car engines with biofuel, i.e. gas that comes from organic matter, typically ethanol made from corn or soy. When you burn biofuel, you’re still injecting carbon into the atmosphere, but only the carbon that was contained in the plants your engine is burning, not carbon that was safely stored in the Earth crust for millions of years. The problem is, the production of ethanol emits vast amounts of CO2 itself, because the agro industry uses tractors and trucks that burn regular petroleum-based diesel, so in the wider scheme of things, biofuel only marginally reduces carbon emissions. Of course, the solution here would be to fuel all agricultural and transportation machines with biofuel as well, which is feasible. So the carbon intensity of fuel-based mobility can be reduced as well; it’s no match for switching to electric vehicles in terms of curbing global warming, but when you consider the carbon cycle, you see that it can be done.

The core problem with fossil fuels

Slightly more complex is the question of carbon additionality. The principle of additionality means that an activity adds something that wasn’t there before.

For carbon, the question is: is your consumption of energy adding carbon in the atmosphere that wasn’t there before (“before” meaning previously to the time when humans started injecting carbon into the air)? The carbon we consume with our cars, boats and power plants came from here, sure, we didn’t add it to our planet from elsewhere, but the vast majority of it wasn’t in the Earth’s current biogeochemical cycles until humans started pulling it out of the ground. In fact, it’s been out of circulation for so long we call it ‘fossil fuel.’ That’s pure additionality right there: these dozens of billions of tons of carbon we produce yearly weren’t in the air, and now they are (“now” meaning within the last 250 years, and especially the last 50), leading to CO2 levels in the atmosphere in 2014 that were 43% above pre-1750 values.

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A coal mine in Inner Mongolia, China. Photo by Herry Lawford. (Source: Flickr)

The situation is completely different with biomass, i.e burning organic matter rather than fossil fuel. This is considered a sustainable source of energy even though it generates CO2, because it’s the origin of the carbon that makes all the difference. When you burn wood, you’re merely sending back into the atmosphere amounts of carbon that were absorbed by the trees most likely a few decades ago at most. And that CO2 will get absorbed by other trees again through photosynthesis in a few years or less, as trees are essentially “solidified air”, as Richard Powers puts it. So in the wide scope of our planet’s functioning, you’re not tipping the scales, merely temporarily moving carbon atoms around.

And that’s the whole problem with fossil fuels. The carbon they contain has no place in the atmosphere. It’s been quietly stored deep in the underground for an extremely long time and our planet has constructed its climatic and biological balance based on that situation. More specifically, the Carboniferous and subsequent Mesozoic periods stocked billions of tons of carbon in our underground through the decay of forests (which became coal) and plankton (which became oil and natural gas) — both phenomena were over before the dinosaurs went extinct, so we’re talking dozens of millions of years here. That stuff was settled before long we came along, and we really shouldn’t have messed with it, disrupting the carbon cycle in ways we only began to understand decades after we started doing it.

Though we know that there have been many periods in the Earth’s history when there was more CO2 in the atmosphere and higher mean temperatures than today, that was the result of slow biogeochemical shifts that happened over millions of years, not 250… Nobody can cope with the speed at which we’re adding carbon into the system right now: no plants, no ecosystems, not even humans. Bottom line is: if it’s in the ground, we really should learn to leave it there.

French-American citizen of the world based in Paris. Former music journalist turned editorial content creator and concerned dweller of Earth.

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