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Using CESM-RESFire to Understand Climate-Fire-Ecosystem Interactions and the Implications for Decadal Climate Variability

Presentation Date
Tuesday, December 8, 2020 at 7:25am



Large wildfires exert strong disturbance on climate systems and ecosystems by perturbing radiative forcing as well as the carbon and water balance between the atmosphere and land surface, while short- and long-term variations in fire weather, terrestrial ecosystems, and human activity modulate fire severity and reshape fire regimes. Here we use the fully interactive REgion-Specific ecosystem feedback Fire model (RESFire) that was developed in the Community Earth System Model (CESM) to investigate these interactions and their impacts on global climate and fire activity. We designed two sets of decadal simulations using CESM-RESFire for present-day (2001–2010) and future (2051–2060) scenarios, respectively, and conducted a series of sensitivity experiments to assess individual feedback pathways among climate, fire, and ecosystems. The implementation of RESFire, which includes online land–atmosphere coupling of fire emissions and fire-induced land cover change (LCC), reproduces the observed burned areas and aerosol optical depth (AOD) and agrees with carbon budget benchmarks. We estimate the global averaged net radiative effect of both fire aerosols and fire-induced LCC at −0.59±0.52 W m−2, which is dominated by fire aerosol–cloud interactions (−0.82±0.19 W m−2), in the present-day scenario. The fire-related net cooling effect increases by ~170 % to −1.60±0.27 W m−2 in the 2050s under the Representative Concentration Pathway 4.5 (RCP4.5) scenario. Such considerably enhanced radiative effect is attributed to the largely increased global burned area (+19 %) and fire carbon emissions (+100 %) from the 2000s to the 2050s driven by climate change. We also evaluate two distinct feedback mechanisms that are associated with fire aerosols and fire-induced LCC, respectively. On a global scale, the first mechanism imposes positive feedbacks to fire activity through enhanced droughts with suppressed precipitation by fire aerosol–cloud interactions, while the second one manifests as negative feedbacks due to reduced fuel loads by fire consumption and post-fire tree mortality. These two feedbacks with opposite effects compete at regional to global scales and increase the complexity of climate–fire–ecosystem interactions and their climatic effects.

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