Slowing Sinks

Every year, deforestation, fossil fuel combustion, and other human-related activity pumps six billion metric tons of carbon dioxide into our atmosphere.

About half of this CO2 remains in the air and is thought to contribute to global warming. But scientists say the other half is absorbed by so-called carbon sinks — for example, the ocean and vegetation on land. David Crisp at the Jet Propulsion Laboratory hopes to begin a global hunt for carbon sinks — by placing a sensitive carbon dioxide measuring tool on a satellite scheduled for launch in 2007.

David Crisp: We don’t know where the sinks are. We don’t what the sinks are. We also don’t know how they might respond over time as the climate changes. In particular we don’t know if they’ll become more or less efficient.

Young forests sop up carbon to build branches, trunks and leaves. But a mature forest grows more slowly and so doesn’t need as much carbon. Ocean sinks might also diminish, says Crisp. A cooler, vigorously circulating ocean absorbs more. If the ocean warms, less carbon will sink into the sea.

David Crisp: There are several reasons to believe that the existing sinks may not continue to function the way they are functioning now, and if that happens, the atmospheric build-up could increase rather dramatically.

Orbiting Carbon Observatory

My forests can suck more carbon than your forests! OK, so you won’t here that on the gradeschool play-yard — but in the future, if the world’s countries agree to slash carbon dioxide emissions, monitoring the amount of carbon that forests absorb could be a critical way to enforce global treaties.

Countries might get credit for reducing the amount of carbon dioxide they dump into the atmosphere — or by showing that forests within their borders a sucking down a lot of the carbon the country produces.

At the moment, it’s not easy to tell how much carbon a forest is absorbing. There are many ground-based measurements in progress to measure local carbon dioxide. There are also projects underway that attempt to use aircraft to map carbon uptake over forests in the U.S. and the Amazon. David Crisp addresses some of the limitations of the more than 100 ground-based sites.

Here’s a bit of chemistry trivia. Dr. Crisp explains that the name “Orbiting Carbon Observatory” was in part chosen so that the acronym for the mission would be OCO. Why?

Carbon dioxide is one carbon molecule surrounded by two oxygen molecules — often written CO2. The bonds that tie the molecule together force the three atoms into a line like this: oxygen-carbon-oxgen — or in shorthand, OCO.

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