(Swan Lake fire on June 18 2019, photo from Alaska Division of Forestry)
In 2019, a prolonged drought and unusual high summer temperature induced an unprecedented fire season in Southcentral Alaska. The average August temperature and precipitation anomalies within the Kenai Peninsula and Susitna Valley were +4.1°C and -126.5 mm respectively. The lightning-ignited Swan Lake Fire started on 5 June 2019 and grew from mid-June through late August. This wildfire resulted in more than $70 million in fire suppression costs, record-breaking degradation of air quality with potential impacts on public health, and economic losses including the disruption of tourism, infrastructure damage and transportation closures. The following questions would arise: Is the 2019 disaster attributed to anthropogenic climate change? Do we expect more fire seasons in the future in Southcentral Alaska like 2019?
Major burn areas of 2019 in southern Alaska and the progression of the Swan Lake Fire
In a recent published study in Land, authors Uma Bhatt, Rick Lader, John Walsh, Peter Bieniek, Richard Thoman, Matthew Berman, and other 17 co-authors, investigated these questions by placing the 2019 fire season into both historical and future contexts, estimating the attribution of anthropogenic climate change and future risks in this region. Using the Standardized Precipitation Evapotranspiration Index (SPEI) as a measure of surface wetness/dryness to represent the fire danger, the areas of Southcentral Alaska affected by the 2019 wildfires have revealed the lowest values since 1979. Relying on climate model simulations from a large ensemble of the Community Earth System Model (CESM) comparing preindustrial and present-day (1979–2019) periods, the authors demonstrated that the anthropogenic forcing has not yet increased the likelihood of extremely low SPEI that would favor the 2019 wildfires in Southcentral Alaska. With increased greenhouse gas emissions following the high-end RCP 8.5 scenario, the model simulations further project trends towards wetter and warmer regional climate conditions that favor opposing changes in SPEI. However, temperature rise turns out to be a dominant negative driver leading to a potential future emergent signal of more frequent negative extremes of the SPEI and hence an increased risk of severe wildfire.
Distribution of SPEI values based on CESM ensemble members
This study was partially funded by the MAPP program.
Read the full paper here
The Modeling, Analysis, Predictions, and Projections (MAPP) Program is a competitive research program in NOAA Research's Climate Program Office. MAPP's mission is to enhance the Nation's and NOAA's capability to understand, predict, and project variability and long-term changes in Earth's system and mitigate human and economic impacts. To achieve its mission, MAPP supports foundational research, transition of research to applications, and engagement across other parts of NOAA, among partner agencies, and with the external research community. MAPP plays a crucial role in enabling national preparedness for extreme events like drought and longer-term climate changes. For more information, please visit www.cpo.noaa.gov/MAPP.