How Fast Can Plants Absorb Our Carbon Emissions? UC Merced Professor Develops New Photosynthesis Measurement Method

MERCED - We count on vegetation to absorb a large portion of the carbon dioxide emitted from the burning of fossil fuels, helping mitigate climate change through photosynthesis. But what happens if the temperature warms enough to change that process? Heat, drought or a shift from snowfall to rainfall caused by climate warming may affect the amount of CO2 absorbed through photosynthesis by vegetation, but how much?

"Our inability to accurately measure and forecast photosynthesis has been responsible for a big part of the uncertainty in our climate change forecasting so far," said Professor Elliott Campbellof the University of California, Merced.

A new study by Campbell and several colleagues in today's issue of the journal Scienceoutlines a method for measuring photosynthesis by quantifying the relationship between CO2 and another form of carbon, carbonyl sulfide, or COS, in the atmosphere. His results - obtained in collaboration with fifteen other scientists from around the United States and other countries - will allow accurate information about photosynthesis to be incorporated into major climate models, helping make climate change forecasts much more reliable.

"Professor Campbell's discovery represents a workable way to measure photosynthesis and a major contribution to climate change science," said Dean Jeff Wright of the UC Merced School of Engineering."The publication of his new paper in Science is a great accomplishment for him and his colleagues worldwide, and a source of pride for our campus."

Campbell found himself spotlighted in media outlets nationwide last year upon the announcement of his research finding that we could meet up to 8 percent of our energy needs by using sustainably produced biofuels - fuels made from crops grown on abandoned farmland, for example.

His new work may have an even bigger impact.

COS is used by plants, in a process parallel to photosynthesis, at about the same rate CO2 is used in photosynthesis. Using COS to measure photosynthesis is more straightforward than using CO2, because while plants do absorb CO2, they also emit it.

The Science study places observed data on North American atmospheric COS and CO2, as well as information gleaned from laboratory experiments, into a 3-D computer model, showing that plants draw COS down from the atmosphere and providing evidence that the relationship between COS and CO2 measurements indicate the rate of photosynthesis.

Campbell said the method he and his colleagues have devised may now be used to analyze large atmospheric carbon datasets assembled by the North American Carbon Program through the National Oceanic and Atmospheric Administration (NOAA) and NASA. Resulting information can be used to refine or even correct the models we now rely on to predict what will happen to our climate in the future.

UC Merced is rapidly establishing itself as a center for climate change research. The Sierra Nevada Research Institute, an interdisciplinary research organization on campus focusing on resource-related research in the Sierra Nevada and the neighboring Central Valley of California, houses major projects investigating precipitation, water supplies, species habitats and more issues hinging on what happens in Earth's warming climate. The UC Merced Energy Research Institute emphasizes research aiming at energy-related approaches to mitigating climate change - solar energy, biofuels, and other sustainable solutions. Campbell is a participating faculty member in both institutes.

The research for this paper was conducted before Campbell arrived at UC Merced earlier this year.

The Science abstract for Campbell's paper can be found online at http://www.sciencemag.org/cgi/content/short/322/5904/1085. Subscribers to the journal can read the entire text online.

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