Severe Global Environmental Issues Caused by Canada’s Record-Breaking Wildfires in 2023

Abstract

Due to the record-breaking wildfires that occurred in Canada in 2023, unprecedented quantities of air pollutants and greenhouse gases were released into the atmosphere. The wildfires had emitted more than 1.3 Pg CO₂ and 0.14 Pg CO₂ equivalent of other greenhouse gases (GHG) including CH₄ and N₂O as of 31 August. The wildfire-related GHG emissions constituted more than doubled Canada’s planned cumulative anthropogenic emissions reductions in 10 years, which represents a significant challenge to climate mitigation efforts. The model simulations showed that the Canadian wildfires impacted not only the local air quality but also that of most areas in the northern hemisphere due to long-range transport, causing severe PM_2.5 pollution in the northeastern United States and increasing daily mean PM_2.5 concentration in northwestern China by up to 2 µg m⁻³. The observed maximum daily mean PM_2.5 concentration in New York City reached 148.3 µg m⁻³, which was their worst air quality in more than 50 years, nearly 10 times that of the air quality guideline (i.e., 15 µg m⁻³) issued by the World Health Organization (WHO). Aside from the direct emissions from forest fires, the peat fires beneath the surface might smolder for several months or even longer and release substantial amounts of CO₂. The substantial amounts of greenhouse gases from forest and peat fires might contribute to the positive feedback to the climate, potentially accelerating global warming. To better understand the comprehensive environmental effects of wildfires and their interactions with the climate system, more detailed research based on advanced observations and Earth System Models is essential.

摘要

2023年加拿大破纪录的野火向大气中释放了大量的温室气体和空气污染物. 截止8月31日, 野火排放了1.3 Pg CO₂以及0.14 Pg CO₂当量的CH₄和N₂O等其它气体温室气体. 野火温室气体排放量超过了加拿大计划10年累积人为减排量的2倍, 对缓解全球变暖的努力构成了显著挑战. 数值模拟结果显示加拿大野火不仅影响局地空气质量, 还会通过长距离传输影响北半球大部分地区. 加拿大野火造成美国东北部地区发生严重的空气污染, 而中国西北部地区日均PM_2.5浓度增加可达2 μg m⁻³. 观测数据也显示纽约市日均PM_2.5浓度高达148.3 μg m⁻³, 为50多年来最恶劣的空气质量, 接近世界卫生组织空气质量指导值(15 μg m⁻³)的10倍. 除了森林大火的直接排放, 地表下的泥炭土可能会持续阴燃数月甚至更长时间, 释放巨量CO₂. 通过排放温室气体, 加剧全球变暖, 野火可能会与全球变暖形成正反馈. 为了全面理解野火的综合环境效应及其与气候系统的相互作用, 亟需基于先进的观测数据和地球系统模式开展深入研究.