Hot Air, Cool Reception
Featured Image Caption: View of the Harz Mountains in the winter (Image source: Hasselfelde (January 2026) 1 by Romzig is licensed under CC0 1.0 Universal License)
Source Article: Liu, S., Wang, Y., & Ren, C. (2026). Cold weather patterns and health impacts across climate regions in a warming world: A systematic review at the global scale. Environmental Impact Assessment Review, 118, 108311. https://doi.org/10.1016/j.eiar.2025.108311
Secondary Sources
Blackport, R., & Fyfe, J. C. (2024). Amplified warming of North American cold extremes linked to human-induced changes in temperature variability. Nature Communications, 15(1). https://doi.org/10.1038/s41467-024-49734-8
Chikoore, H., Mbokodo, I. L., Singo, M. V., Tumelo Mohomi, Munyai, R. B., Henno Havenga, Mahlobo, D. D., Engelbrecht, F. A., Bopape, M.-J. M., & Thando Ndarana. (2024). Dynamics of an extreme low temperature event over South Africa amid a warming climate. Weather and Climate Extremes, 44, 100668–100668. https://doi.org/10.1016/j.wace.2024.100668
Acknowledgments
A special thanks to Professor Mary Beth Decker, Professor of Ecology and Evolutionary Biology at Yale University, for her phenomenal insight and advice.
You May be Wondering… so What Happened to Global Warming?
I don’t know about you, but I have not been feeling particularly warm the past few days. Unfortunately, I must admit the weather has been making my Canadian heart quite happy, but I do truly empathize with the unhoused folks.
A central debate topic over the climate crisis is: If the planet is really warming, then why has it been so cold lately? Let’s break it down together. There are two major definitions when it comes to talking about climate change: 1) weather and 2) climate. Weather is the daily temperatures you feel outside, and climate is that same weather pattern observed over a much longer stretch of time. Part of the confusion is the relationship between weather and climate. A warming climate doesn’t just mean uniformly warmer weather; in fact, it destabilizes the systems that keep our seasons predictable.
For instance, there is the Polar Front, the boundary between cold Arctic air and warmer mid-latitude air. As the Arctic warms on average faster than the rest of the planet, this boundary weakens, causing the jet stream to become unstable. This leads to cold arctic air that spills further south, producing those jarring cold snaps that can make climate change feel like a myth, when in reality, these weather changes might be a consequence of a warming planet.
The whiplash between a bitter winter cold and a sudden warm spring may feel disorienting, but this variability is directly linked to climate change. A recent study published in Environmental Impact Assessment Review explores how these cold weather events, also known as extreme cold events, are not just meteorological curiosities, but genuine threats to human health.
Previous research on this topic has been surprisingly narrow. Most studies focused on a single health outcome, a single region, or one specific type of cold event, leaving big gaps in our understanding of how cold weather affects people across different climates and cultures. Researchers at the University of Hong Kong set out to fill those gaps with a sweeping systematic review of 163 studies spanning 48 countries and 15 climate zones.
So, What Did They find? Cold is Complicated and Increasingly Hard to Define.
The team identified three main ways scientists define a cold event: percentile-based definitions (when temperatures dip below a historically low threshold for several consecutive days), fixed threshold definitions (when temperatures fall below a specific absolute value, like 12°C), and temperature fluctuation-based definitions (which capture abrupt day-to-day or within-day temperature swings). Each approach has its strengths, but crucially, none of them tells a complete story on its own.
Here’s where it gets interesting. As the planet warms, winters aren’t just getting milder. They’re actually getting more variable. The researchers found that over 60% of the global land area is now experiencing more frequent and intense temperature fluctuation events– dramatic swings from unseasonably warm days to sudden bitter cold. This pattern is especially pronounced in East Asia, eastern North America, and parts of South America. Yet most cold-weather warning systems are still built around old assumptions about simple, sustained cold snaps, rather than the volatile temperature rollercoasters we have today.
The health stakes are significant. The study catalogued cold weather’s links to 58 different health outcomes. The most established connections are to cardiovascular and respiratory diseases, with cold events tied to increased mortality, hospitalizations, and even longer hospital stays and higher healthcare costs. Research also shows results stratified by age, consistently noting that people over 65 are the most vulnerable to adverse health outcomes tied to cold events. Perhaps more surprisingly, cold events are also linked to mental health: depression, schizophrenia, bipolar disorder, and adolescent psychiatric emergencies across studies in the US, China, Switzerland, and Sweden.
One of the study’s most pressing takeaways is the mismatch between what scientists measure and the capacity of public health systems. Research tends to use mean daily temperature, while cold-weather warning systems typically rely on minimum daily temperature. Percentile-based research findings are difficult to translate into the fixed-threshold alerts issued by meteorological offices. The result? Warning systems that may be leaving vulnerable people exposed, particularly as sudden temperature drops are becoming the new norm.
The researchers propose a framework to help bridge this gap, encouraging future studies and public health providers to choose their cold event metrics based on local climate patterns and the specific health outcomes they’re trying to address.
So, the next time the temperature nosedives without warning, know that it isn’t necessarily evidence against climate change; quite frankly, it may be a consequence and potential public health emergency.
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