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Carbon dioxide: Where does it go?

Few of us think about the state of the atmosphere until it fails to provide us with a hospitable environment. More often than not, human activities are behind atmospheric ills. Climate change and high concentrations of particulate matter are only two examples.

Most of us are aware of the effects of fossil fuel consumption on the atmosphere. Our dependence on power plants and automobiles has increased carbon dioxide emissions at an alarming rate.

Worldwide, the loss of natural vegetation caused by deforestation further adds to atmospheric carbon dioxide,―making climate change one of the most important issues today.

There is little doubt that increasing carbon dioxide emissions and climate change will continue unless we act to curb them. There are, however, some mysteries that remain unsolved.

For decades, scientists have been trying to understand why the total amount of carbon dioxide emitted by human activities is about 2 billion metric tons greater than estimates of the carbon dioxide that accumulates in the atmosphere and the oceans. What is behind the imbalance in the carbon budget? Or, more simply put,―why isn’t there even more carbon dioxide in the atmosphere?

Scientists speculate some type of mechanism is removing carbon dioxide from the atmosphere, preventing a sharp spike in atmospheric levels, even as carbon emissions have jumped by 40 percent in the past 20 years.

This unknown storage of carbon, known as the "missing sink," has researchers scrambling to find out where carbon dioxide is accumulating. Many studies suggest the uptake occurs in terrestrial ecosystems such as forests, but more data are needed.

Solving the mystery of the missing sink will take a concerted effort. Observing networks will play an essential role in elucidating what causes changes in carbon dioxide in our atmosphere.

The Cary Institute has recently joined that effort by adding a carbon dioxide monitor to its long-term Environmental Monitoring Program. Working around the clock, the instrument (Li-Cor LI-840 CO2/H2O analyzer) will continuously measure the air’s carbon dioxide and water content. Data will be sent to a microcomputer, which will calculate and store three-minute averages.

With this high-resolution data, we join colleagues at institutions such as the Lamont-Doherty Earth Observatory in trying to understand local and regional changes in atmospheric carbon dioxide, and, ultimately, the origin of the missing carbon sink.

Carbon dioxide is only one of the problems plaguing our atmosphere today. Humans are responsible for a host of air pollutants, including many that directly affect our health. In the summer, forecasters often provide air quality alerts for pollutants such as ozone and particulate matter.

Since it is a primary cause of asthma, particulate matter is of concern to human health. The concentration of fine particles in the air is directly correlated with emergency room visits for breathing difficulties. Where the particulate matter comes from, what it consists of and how it is transported are critical to understand if we want to control fine particles.

In our region, particulate matter consists largely of ammonium sulfate. The sulfate originates from sulfur dioxide from the burning of coal; the ammonium comes from ammonia emissions from agricultural fertilizers and livestock. It is important to understand the origin of both those emissions: Are they emitted locally, or are they transported here?

While we have a good understanding of sulfur dioxide and its cousin, sulfate, we have a poor understanding of ammonia and ammonium. We know ammonia comes from agriculture, but we know little about how and where it is converted to ammonium.

The Cary Institute has collected ammonium data from air particles and precipitation since 1988. Recently, the Cary Institute joined a nationwide program called the Ammonia Monitoring Network. It is part of a national pollution monitoring program called the National Acid Deposition Program, which gives an understanding of the pollutants causing acid rain and other problems.

New ammonia and carbon dioxide monitoring equipment will allow our Environmental Monitoring Program to study two important atmosphere-related environmental problems.

By continuing to provide data and expertise, the Cary Institute is committed to contributing to environmental solutions.

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