Enhanced fire-prone weather under greenhouse gas warming can significantly affect local and global carbon budgets from increased fire occurrence, influencing carbon-climate feedbacks. However, the extent to which changes in fire-prone weather and associated carbon emissions can be mitigated by negative emissions remains uncertain. Here, we analyze fire weather responses in CO2 removal climate model experiments and estimate their potential carbon emissions based on an observational relationship between fire weather and fire-induced CO2 emissions. The results highlight that enhanced fire danger under global warming cannot be restored instantaneously by CO2 reduction, mainly due to atmospheric dryness maintained by climatic inertia. The exacerbated fire danger is projected to contribute to extra CO2 emissions in 68% of global regions due to the hysteresis of climate responses to CO2 levels. These findings highlight that even under global cooling from negative emissions, increased fire activity may reinforce the fire-carbon-climate feedback loop and result in further socio-economic damage.
Devastating fire occurrences worldwide have garnered the growing attention of the academic community and the public. These wildfires inflict not only instantaneous socio-economic damages but also have long-lasting impacts on the Earth system by providing carbon dioxide (CO2) and aerosols to the atmosphere, altering landscape compositions, and disturbing the ecosystem. One of the most critical impacts on shaping our future is the significant amount of CO2 released into the atmosphere, leading to the positive feedback that amplifies global warming. The annual total of fire carbon emissions (CFire) is estimated to be 21–36% of man-made emissions (2000-2020), with an average of ~2 PgC per year (1 PgC = 1015 g of carbon). Being such a major carbon emitter, the trend towards more frequent large fires raises concerns about further climate change in the future.
An accurate future fire prediction is crucial but challenging due to the complexity of fire dynamics related to multiple factors such as fuel availability, ignition agents, human control, and weather conditions. Nevertheless, weather conditions are generally considered critical factors in shaping recent and future fire trends. Indeed, there is a broad consensus that anthropogenic climate change toward warmer and drier conditions will exacerbate fire danger. However, estimations for future carbon emissions from increased fires are still uncertain.
Meanwhile, recent studies have reported that the climate system exhibits hysteresis with respect to the reduced CO2 forcing. That is, the climate state is not immediately recovered even if the CO2 concentration is returned to the previous level-for instance, the global surface temperature still remains high due to the large thermal inertia of the ocean, the recovery of the weakened thermohaline circulation (THC) is delayed, and the latitudinal position of the Intertropical Convergence Zone (ITCZ) stays at south compared to its original position. The associated changes in surface weather are not experienced homogeneously across regions and/or variables. However, its influence on fire danger remains unexplored, causing uncertainty about how fire weather will respond to global cooling under carbon reduction policies.
Minimizing these uncertainties will allow more accurate climate predictions and the prioritization of effective mitigation and adaptation strategies. Understanding the internal feedback processes within the climate system, specifically isolating the effects of climate change from non-climatic factors, will greatly benefit achieving these goals. Therefore, this study investigates global and regional responses of fire weather to an idealized CO2 removal scenario using climate model simulations. Also, a quantitative assessment of the potential carbon release from increased fires is conducted at global and country levels. Our findings demonstrate that fire danger persists even after CO2 reduction due mainly to the thermal inertia of the climate system, which in turn can accumulate a significant amount of carbon in the atmosphere. The global trend of prolonged fire danger is regionally modulated by atmospheric and oceanic circulations and this information would support the national greenhouse gas (GHG) inventory management.
Source:
Nature Communication
https://www.nature.com/articles/s41467-024-54339-2 .
Provided by the IKCEST Disaster Risk Reduction Knowledge Service System
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