Smoke That Cooled the Hemisphere: The Global Fallout of Canada’s 2023 Wildfires

Ruddy Crake

15-09-2025

Smoke flies out from the cave, even faintly, but it is enough to make Kingfisher squeamish and almost blackout.

In “A Shocking Secret”; Wild Wise Weird [1]

© Wix

The summer of 2023 saw Canada experience its worst wildfire season in recorded history, with fires burning nearly 5% of its forest area—seven times the national average for the past four decades [2]. The carbon released was comparable to the annual fossil fuel emissions of major industrial nations, injecting vast amounts of smoke and aerosols into the atmosphere [3]. But what did this mean for the climate beyond Canada’s borders?

A new study by Roșu and colleagues [4] used a state-of-the-art Earth system model to simulate the atmospheric effects of these wildfires. The results reveal dramatic consequences. Aerosols from the fires spread across much of the Northern Hemisphere, decreasing average surface air temperature by nearly 1 °C. Locally, the cooling was even stronger—up to −5.4 °C in parts of Canada and −2.63 °C in Eastern Europe and Siberia. This cooling arose from smoke particles blocking sunlight and from increased cloud cover triggered by aerosols. In effect, the fires temporarily altered hemispheric weather patterns, with circulation changes resembling the Arctic Oscillation in its negative phase.

The findings underscore how extreme fires can act as “climate shapers,” producing not only devastating local damage but also remote and long-lasting atmospheric anomalies. Crucially, the same smoke that cooled the hemisphere also worsened air quality, with health consequences for millions exposed to toxic haze [5,6]. Scientists warn that as climate change drives hotter and drier conditions, such megafires are likely to become more frequent [7].

The wildfires were intensified by human-driven warming, yet in turn they reshaped the climate system we all depend on [8]. Recognizing these feedbacks cultivates the Nature Quotient (NQ)—the intelligence to perceive ecological interdependence and act with foresight. Strengthening NQ means acknowledging that cutting fossil fuel emissions is inseparable from preventing future megafires, protecting forests, and safeguarding atmospheric stability [9].

References

[1] Vuong QH. (2024). Wild Wise Weird. https://books.google.com/books?id=N10jEQAAQBAJ

[2] Jain P, et al. (2024). Drivers and impacts of the record-breaking 2023 wildfire season in Canada. Nature Communications, 15, 6764. https://www.nature.com/articles/s41467-024-51154-7

[3] MacCarthy J, et al. (2024). Extreme wildfires in Canada and their contribution to global loss in tree cover and carbon emissions in 2023. Global Change Biology, 30, e17392. https://doi.org/10.1111/gcb.17392

[4] Roșu LA, et al. (2025). Large-scale impacts of the 2023 Canadian wildfires on the Northern Hemisphere atmosphere. npj Clean Air, 1, 22. https://www.nature.com/articles/s44407-025-00022-9

[5] Reid CE, et al. (2016). Critical review of health impacts of wildfire smoke exposure. Environmental Health Perspectives, 124, 1334-1343. https://doi.org/10.1289/ehp.1409277

[6] Cyr D, et al. (2022). Mitigating post-fire regeneration failure in boreal landscapes with reforestation and variable retention harvesting: At what cost? Canadian Journal of Forest Research, 52, 568-581. https://doi.org/10.1139/cjfr-2021-0180

[7] Jain P, et al. (2024). Record-breaking fire weather in North America in 2021 was initiated by the Pacific northwest heat dome. Communications Earth & Environment, 5, 202. https://www.nature.com/articles/s43247-024-01346-2

[8] Nguyen MH. (2024). How can satirical fables offer us a vision for sustainability? Visions for Sustainability, 23(11267), 323-328. https://doi.org/10.13135/2384-8677/11267

[9] Vuong QH, Nguyen MH. (2025). On Nature Quotient. Pacific Conservation Biology, 31, PC25028. https://doi.org/10.1071/PC25028