Fire Affects Global Land Temperatures and Energy Flows by Restructuring Ecosystems
Fire is a global phenomenon that affects the biosphere and climate in complex ways. Only complex Earth system models (ESMs) can provide an integrated, consistent picture of these effects, which are not well understood. To address this, a scientist at the U.S. Department of Energy’s Pacific Northwest National Laboratory contributed to a study that compared “fire-on” and “fire-off” ESM simulations for the 20th century
This study provided the first quantitative assessment of fire’s influence on global land temperatures and energy flows, documenting the subsequent effect on terrestrial ecosystems.
Knowing exactly how fire affects climate at a global scale—whether by sending smoke to the atmosphere, changing the light environment of ecosystems, or another mechanism—requires complex ESMs with realistic fire capabilities. Researchers in this study used the Community Earth System Model to provide the first quantitative assessment of fire’s influence on the global annual land surface air temperature and energy budget. The model simulates the Earth’s atmosphere, ocean, land, and sea ice. For the 20th century, fire-induced changes in terrestrial ecosystems significantly increased global land annual mean surface air temperature by 0.18 degrees Celsius, and decreased surface net radiation and latent heat flux (the energy carried away by the evaporation of water) by 1.08 W m−2 and 0.99 W m−2, respectively. However, the changes had limited influence on sensible heat flux and ground heat flux. Fire effects were most clearly seen in the tropical savannas. These results suggest that fire-induced damage to the vegetation canopy increases surface air temperature predominantly by reducing latent heat flux.