The Mystery of the Missing Carbon

July 2, 2015

NOTE: Images in this archived article have been removed.

It’s a whodunit with huge consequences for life on Earth.

Somehow, a whole lot of atmospheric carbon dioxide (CO2) has gone missing and it’s becoming a scientific detective story to figure out where it went and why. The Principle Investigator into this mystery is NASA, which launched a satellite called the Orbiting Carbon Observatory-2 (OCO-2) on July 2nd, 2014, into an orbit around the Earth in hopes of cracking the case.

OCO-2 is designed to precisely measure carbon dioxide levels in the atmosphere, in particular the amounts that are “inhaled and exhaled” annually by living things on the planet. This ‘breathing’ pattern was first discovered by Dr. Charles Keeling and is captured beautifully in the famous Keeling Curve (see: The cause of the breathing pattern is the relationship between sources (emitters) and sinks (absorbers) of CO2. Carbon sources include: fossil fuel combustion, forest fires, decaying organic matter, and the biowaste created by micoorganisms. Carbon sinks include: green plants, oceans, rocks, and soil. The planet ‘breathes in’ when the sinks are working at maximum efficiency (ie summer, when plants are greenest) and ‘breathes out’ when they are not (winter). This breathing becomes a discernable pattern (the Keeling Curve) because there are more deciduous trees, which drop their leaves in the fall, in the northern hemisphere than in the southern.

This breathing is part of the great carbon cycle, by which carbon molecules travel from source to sink to source to sink, round and round. It’s nature’s way of keeping carbon in balance, especially if there’s been a natural disruption. If too many volcanoes go off in a short amount of time, for instance, CO2 levels can rise to very high levels. Or if plants die off as the result of an ice age, levels can fall dramatically. In all cases, when these imbalances occur, the sinks and sources work to restore an equilibrium and get the planet breathing ‘normally’ again – a process, by the way, that takes thousands or millions of years.

Unfortunately, humans have been provoking an asthma attack on Earth since the Industrial Revolution, principally by digging up and burning 300-million-year old carbon in the form of coal, oil, and natural gas. In terms of quantity and speed, it’s a source of CO2 that the planet has never experienced before, which means sinks have never had to work this hard in so short a period of time to soak up all this new carbon – the oceans especially – which is where the mystery come in.

Of the billions of tons of CO2 that are currently being pumped into the atmosphere every year as a consequence of human activity (up by a factor of three since the 1950s), approximately 50% stays there, causing global warming. The other 50% is being soaked up by the plant’s sinks, scientists say, with oceans accounting for 27%. That means 23% is going into the land sink, principally green plants, but no one knows precisely where! This is important because encouraging a particular sink to become even more efficient could soak up additional CO2 and help combat climate change.

So where is the missing 23% of the CO2 that we are pumping into the atmosphere going? The authors of most of the articles that I read assume its being taken up by new vegetation, trees specifically. That’s because more plants = more photosynthesis = more soaking up of CO2, which gets stored as biomass in the tree or plant. That’s great news, except for one thing: scientists can’t find a corresponding amount of new trees and plants! The main suspects are the Amazon and the boreal forests of North America and northern Europe, but scientists haven’t been able to correlate new growth in either ecosystem with all that missing carbon. It is presumed that OCO-2 will identify the specific forested culprit.

But what if we’ve got the wrong suspect in mind?

An obvious answer, to me anyway, is soil. There is a great deal of scientific evidence that biologically-rich soil covered with green and growing plants can sequester significant amounts of atmospheric carbon via photosynthesis. However, none of the articles I read about the missing 23% mentions the soil. A good example is a fascinating article in National Geographic titled ‘The Case of the Missing Carbon’ (

The author writes that that ability of trees and plants to “put on weight” accounts for the missing carbon. However, he notes, even when this ‘extra weight’ is tallied, there is still 1.5 billion tons of carbon missing! Could it be the soil? The author doesn’t say – because he doesn’t mention soil as a sink at all.

This is a common oversight, unfortunately. When it comes to carbon sinks and the role they can play in combating climate change (remember, 50% of the new CO2 being manufactured today is being absorbed by planetary sinks), the focus is almost always on trees and shrubs. Like Cinderella, soils aren’t invited to the party. This is a crime because it’s been well established that soils have the potential capacity to soak up large amounts of CO2. I suspect this ‘mystery’ isn’t a mystery at all – all that ‘missing’ carbon is being stored in soils!

Hopefully, OCO-2 will corroborate my hunch. If it does, then perhaps we can take a big step towards recognizing the potential of soil to assist in the fight against climate.

Here’s a photo of the usual suspect:

Image Removed

There’s another culprit in this mystery: the U.S Congress.

In recent years, in response to rising concerns about the Earth’s geophysical environment and the impact humans are having on it (and vice versa), NASA launched a series of satellites into orbit to precisely measure various conditions on the planet. Five of these satellites fly in a tight cluster called the A-Train (after a popular swing-era tune), one of which is OCO-2. In addition to carbon dioxide levels, the A-Train records data about airborne pollutants, water vapor, clouds, vegetation, and much more. The goal is to create a synchronous ‘snapshot’ of a specific part of the Earth from multiple perspectives, which will help us humans guide our decisions and actions (hopefully).

Congress, however, wants to dismantle the A-Train. In May, the House Committee on Science, Space and Technology voted to gut NASA’s budget for its earth science programs by roughly 25%. Committee chairman Lamar Smith (R-Texas), an avowed skeptic of global warming science, said that NASA should be focusing on space, not Earth. NASA Administrator Charles Bolden shot back by saying the budget cuts would “set back generations worth of progress in better understanding our changing climate, and our ability to prepare for and respond to earthquakes, droughts and storm events.”

The Committee’s proposed cuts boggle the mind – but not more than their hypocritical reasoning, if you can call it reasoning at all. Here’s an illustration: Smith wrote an op-ed for the Wall Street Journal in which he said “Instead of letting political ideology or climate ‘religion’ guide government policy, we should focus on good science. The facts alone should determine what climate policy options the U.S. considers.”

Except – if you eliminate the satellites, you have no data! How can decisions be based on the facts without any facts? I’m not naïve enough, of course, to know what’s really going on here, but it staggers the mind nonetheless. It’s one thing to dispute the data or conclusions based on facts, but it’s another to block the fact-gathering itself. Here’s Smith again: “We don’t know enough yet to make decisions that are going to hurt our economy or hurt the American people. Let’s continue to gather the facts, make sure the science is correct.”

Incredible. Call it The Case of the Missing Data. The criminal is Congress and the murder victims are future generations of Americans.

I don’t know the answer to this mystery other than hope for more democracy. We know what to do about carbon – stop burning it and start storing it – but I don’t know what to do about a political ideology that not only rejects scientific conclusions but actually blocks their formulation. Vote ‘em out of office, I suppose, and pray that their replacements are more willing to gather data and accept scientific consensus. But figuring that out is beyond my pay grade.

In the meantime, I’ll keep rooting for NASA’s A-train! Here’s an illustration:

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Courtney White:

Coming in September, my new book Two Percent Solutions for the PlanetPre-order:

Courtney White

A former archaeologist and Sierra Club activist, Courtney dropped out of the 'conflict industry' in 1997 to co-found The Quivira Coalition, a nonprofit dedicated to building bridges between ranchers, conservationists, public land managers, scientists and others around the idea of land health. Today, his work concentrates on building economic and ecological resilience on working landscapes, with a special emphasis on carbon ranching and the new agrarian movement. His writing has appeared in numerous publications, including Farming, Acres Magazine, Rangelands, and the Natural Resources Journal. His essay The Working Wilderness: a Call for a Land Health Movement" was published by Wendell Berry in 2005 in his collection of essays titled The Way of Ignorance. In 2008, Island Press published Courtney's book Revolution on the Range: the Rise of a New Ranch in the American West. He co-edited, with Dr. Rick Knight, Conservation for a New Generation, also published by Island Press in 2008. He lives in Santa Fe, New Mexico, with his family and a backyard full of chickens.

Tags: carbon cycle, carbon sequestration, fossil fuel greenhouse gas emissions