Liu, Yongqiang (USDA Forest Service, 320 Green Street, Athens, GA, 30602; Phone: 706-559-4240; Email: yliu@fs.fed.us)

CO₂ Emissions from Wildfires in the U.S.: Present Status and Future Trends

Y. Liu *, J. Stanturf, H. Tian, J. Qu

Wildfires can contribute to regional carbon cycle and climate change by releasing a large amount of CO₂ into the atmosphere. Climate change, on the other hand, can affect fire emissions by modifying the environmental conditions for fire ignition and spread. This study seeks to understand the role of wildfires in the United States in atmospheric carbon cycle and the possible disturbance due to global warming. Total emissions of CO₂ from wildfires are first estimated using a set of historical fire data from the USDA Forest Service and other federal agencies. The impacts of the global warming on fire emissions are then assessed based on their relationships with temperature and precipitation, and the projected climate change. The results show an average of annual CO₂ emissions on the order of 10^-1 petagrams of carbon from wildfires. Large interannual variability is found in the fire emissions during the past two decades. High temperature is the most conducive atmospheric condition for strong wildfire emissions in most U.S. regions. Dry weather also contributes to strong emissions. The model-projected U.S. climate change in response to the greenhouse effect is expected to have a major impact on wildland fires and, therefore, the related CO₂ emissions. The changes in temperature and rainfall would play opposite roles by increasing and decreasing the emissions, respectively. The change in temperature, however, is much more important during the wildfire season in the western U.S. It is estimated that the magnitude of the nationwide emissions would be nearly doubled by the mid-21st century.