A recent study conducted by researchers at Harvard University has quantified the impact of climate change on wildfire smoke exposure in the western United States.The findings indicate that nearly half of the harmful wildfire smoke exposure in this region can be directly attributed to human-caused climate change, highlighting the urgent need for effective fire management strategies and pollution control measures.
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phys.orgseas.harvard.eduThe study, published in the Proceedings of the National Academy of Sciences, reveals that climate change accounts for 60-82% of the total burned area in western US forests and 33% in central and southern California since the early 1990s.This translates to an average of 65% of total fire emissions in the US between 1997 and 2020.
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seas.harvard.eduFrom 1997 to 2020, researchers found that almost half of the most dangerous types of wildfire smoke, known as fine particulate matter or PM2.5, can be traced back to climate change.Specifically, climate change was responsible for 58% of the increase in PM2.5 levels from 2010 to 2020.
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phys.orgThe research utilized a combination of observational data, machine learning models, and large climate models to draw its conclusions.The analysis demonstrated how changing weather patterns and rising temperatures have influenced wildfire behavior over the past three decades.For instance, areas such as northern California, Oregon, Washington, and Idaho experienced climate-driven smoke that constituted 44-66% of total PM2.5 levels between 2010 and 2020.
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seas.harvard.eduLoretta Mickley, the lead researcher and senior research fellow at Harvard SEAS, emphasized the necessity of understanding how climate change exacerbates smoke exposure."Our goal was to quantify how much climate change has amplified and exacerbated smoke exposure in the western US," she stated.The findings aim to encourage more thoughtful land and wildfire management practices, as well as increased efforts to mitigate greenhouse gas emissions.
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phys.orgThe study also noted a significant decline in pollution from other sources, such as factories, which dropped by approximately 44% between 1997 and 2020, thanks to regulations like the Clean Air Act.In contrast, wildfire smoke has steadily increased during the same period, posing a growing public health risk.
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seas.harvard.eduWildfire smoke is particularly dangerous due to its composition of fine particulate matter, which can penetrate deep into the lungs and enter the bloodstream, leading to serious health issues such as respiratory problems, cardiovascular diseases, and other long-term health effects.
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lung.orgThe American Lung Association's 2025 "State of the Air" report further underscores the severity of air quality issues linked to wildfires.It found that 156 million people in the US live in areas with unhealthy levels of air pollution, exacerbated by extreme heat and wildfires.
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lung.orgLooking ahead, the Harvard research team is exploring how historical fire suppression practices may have intensified the impact of climate change on wildfire activity.Dense forests and accumulated underbrush, resulting from decades of fire suppression, could be contributing to increased wildfire severity and smoke exposure.
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seas.harvard.eduMickley and her team advocate for proactive measures, such as prescribed burns in high-risk areas, to manage fire risk more effectively.Prescribed burning can help reduce underbrush and limit the potential for catastrophic wildfires in the future, ultimately improving air quality and public health outcomes.
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phys.orgIn conclusion, the link between climate change and increased wildfire smoke exposure is becoming increasingly clear.As wildfires continue to threaten health and safety across the western US, it is essential for policymakers and communities to prioritize sustainable land management and climate action to mitigate these risks.
