Tracing Wildfire-Derived Carbon Monoxide: Insights into Global Transport and Atmospheric Impacts Using a Chemistry-Transport Model

Carbon monoxide (CO) is a key atmospheric trace gas generated from both natural sources, such as biomass burning and volcanic activity, and human-related activities, including vehicle emissions, agricultural practices, and industrial operations. CO plays a key role in atmospheric chemistry as a precursor for tropospheric ozone (O₃) in the background atmosphere, thereby influencing the oxidative capacity of the global atmosphere. Elevated CO concentrations are linked to adverse effects on air quality, human health, and also climate, particularly through O₃ and CO₂ formation.

A growing concern is the contribution of wildfires to CO emissions, as their frequency and severity have risen in response to climate change. CO released from wildfires has immediate effects on air quality and long-term implications for atmospheric composition, making it critical to evaluate its role in air quality, climate dynamics, and public health.

In this study, we use the TM4-ECPL global chemistry and transport model, a highly validated and widely used tool, to examine the pathways and impacts of wildfire-related CO. Our analysis incorporates historical emissions data from the advanced Climate Model Intercomparison Project 6 (CMIP6) database. To achieve regional specificity, we use 13 tracers aligned with the 13 source regions identified by the Hemispheric Transport of Air Pollution version 2 (HTAPv2) framework. Model simulations are driven by ERA-interim meteorology and cover a 20-year period (1995–2015), allowing the analysis of climatological trends and prominent biomass burning events. The contributions of regional CO emissions and their transport across the global ocean are calculated, shedding light on their influence on atmospheric composition and global air quality.

We find that ENSO has a significant impact only on the CO emitted from South East Asia, where from all other source regions we see minimal deviation from the average climatological data. Furthermore, we find that Southern African emitted pollution has the greatest potential impact on the global ocean, with South East Asia being a major contributor in the North and South Pacific and Indian Ocean, and South America a major contributor in the South Pacific.