Quantifying CO2 forcing effects on lightning, wildfires, and climate interactions

Climate change affects lightning frequency and wildfire intensity globally. To date, model limitations have prevented quantifying climate-lightning-wildfire interactions comprehensively. We exploit advances in Earth System modeling to examine these three-way interactions and their sensitivities to idealized CO2 forcing in 140-year simulations. Lightning sensitivity to global temperature change (+1.6 +/- 0.1% per kelvin) is mitigated by compensating atmospheric effects. Global burned area sensitivity to temperature (+13.8 +/- 0.3% per kelvin) is largely driven by intensified fire weather and increased biomass but marginally by lightning changes. We find a universal law characterizing regional-scale modeled fire activity and its CO2 sensitivity, consistent with basic principles of statistical mechanics. Last, a negative climate feedback through intensified aerosol direct effect from fire emissions reaches an equivalent decrease of 0.91 +/- 0.01% in CO2 radiative forcing. However, this feedback contributes to polar amplification. Our analysis shows that climate-lightning-wildfire interactions involve multiple compensating and amplifying feedbacks, which are sensitive to anthropogenic CO2 forcing.