Drought Leaves More CO2 in Atmosphere

Severe drought across North America in 2002 cut in half the continent's natural ability to absorb carbon dioxide from the atmosphere, according to new research from the National Oceanic and Atmospheric Administration (NOAA).

Using the agency's new CarbonTracker modeling system, NOAA researchers found that soil and vegetation across North America were able to absorb only 330 million metric tons of carbon dioxide during the dry year of 2002, compared to an annual average of 650 million metric tons. That left as much extra
carbon dioxide in the atmosphere as the annual emissions of more than 200 million cars.

NOAA scientists found a similar result during Europe's record-breaking drought and heat wave in 2003. Those conditions left Europe with more than 500 million extra tons of carbon dioxide in the atmosphere.

"Scientists often look at the role of greenhouse gases in producing climate extremes," said Wouter Peters, lead researcher in the study and a scientist at the Wageninen University and Research Center in The Netherlands. "Here we show the reverse is also true. Climate extremes can have a major affect on the amount of carbon dioxide in Earth's atmosphere."

During 2002, North America experienced one of its worst droughts in over a century, with nearly 45 percent of the U.S. seeing "extreme" or "exceptional" conditions. The drought had a major impact on the continent's natural carbon sinks: forests, grasslands, farm crops and soil.

Across North America, people annually produce some 1.85 billion metric tons of carbon dioxide emissions. Sources of those emissions include fossil fuels and cement manufacturing. Soils and plants normally absorb about one-third of that amount. In fact, forests that become re-established on former logging areas or abandoned farms can increase a region's carbon dioxide uptake considerably. NOAA researchers found such impacts in Canada's evergreen forests, and along the East Coast and in the Midwest in the U.S.

"Disruptions to natural carbon uptake can have enormous environmental and economic effects, possibly even erasing efforts to reduce fossil fuel emissions in a given year," Peters said. "CarbonTracker not only tells us when and where such disruptions occur, but also suggests why."

CarbonTracker, which uses data from 28,000 atmospheric monitoring sites across the globe, enabled NOAA scientists to compile the first-ever weekly record of carbon dioxide emissions and absorption rates across North America between 2000 and 2005. NOAA researchers will present their findings about the North American carbon cycle this week at the 50th anniversary Global Carbon Dioxide Record Symposium and Celebration.

National Oceanic and Atmospheric Administration, "NOAA Researcher: 2002 Drought Left Millions of Tons of Extra Carbon Dioxide in Earth's Atmosphere." URL: (http://www.noaanews.noaa.gov/stories2007/20071126_cardioxideb.html)