New evidence of the link between carbon dioxide emissions and climate change in boreal ecosystems

Dr Kevin Robert Gurney, assistant professor in the Earth & Atmospheric Science/Agronomy at Purdue University and Associate Director of the Purdue Climate Change Research Center, presented these results at the “Is a Warmer Arctic Adding Carbon Dioxide to the Atmosphere” session of American Association for the Advancement of Science meeting in San Francisco, CA on December 17th.

The research examined the variations in carbon flux from boreal ecosystems, uncovered by the “inverse” method, in relation to measurements of temperature, precipitation and climate indices. The study shows that Boreal N America removes carbon from the Earth’s atmosphere during years in which the region experiences warm Spring temperatures and rainfall. Boreal Asia, however, exhibits an opposing response – years with above normal Fall temperatures and rainfall result in net carbon emissions. “A warming Canada may mean Canadian forests will act as a sink to atmospheric CO2,” said Gurney, “while boreal Asia could lose ecosystem carbon to the atmosphere as the regions warms.”

The results are directly applicable to climate change studies which attempt to link the land and ocean carbon cycles to future warming. Some studies have shown an additional temperature increase (above that derived from industrial greenhouse gases) due primarily to carbon emissions from warmed global soils. The research presented by Gurney suggests that this may occur in Asia but not in North America. “This should help us perform better projections

The results for Boreal North America are further linked to El Nino events. “The greater uptake in Springtime Boreal North American in warm, wet years appears to be related to the El Nino/Southern Oscillation,” said Gurney. “The teleconnection is remarkable, you can see the tropical pacific temperature patterns associated with El Nino travel north and impact boreal North America, inducing greater uptake”.

Temperature and Precipitation are not the only drivers of ecosystem carbon exchange, noted Gurney, but approximately one-half of the variations in Spring and Fall carbon exchange were explained by variations in Temperature and Precipitation. “Human activity such as harvest or fire can also have a large impact on these systems and we are turning to exploring those next”.