Satellite Study Reveals Cold-Climate Cities are Warming Fastest due to Climate Change
For a long time, the threat of extreme temperatures has been associated with arid and hot cities such as Phoenix or Cairo. Cold-climate cities rarely feature prominently on lists of concerns when discussing heatwave emergencies. However, a global scan of 1,400 cities has overturned this logic.
Recent research shows that the regions with the fastest warming rates over the last two decades are not those that were already scorching. The surge in heat exposure in these urban areas is growing far more rapidly than can be explained by population growth alone.
A study led by Marzie Naserikia, a climate researcher at the University of New South Wales (UNSW) in Sydney, Australia, analysed satellite data spanning approximately 20 years. The satellites recorded land surface temperatures—the heat radiating from asphalt, building roofs, and open ground—rather than the air temperature typically measured by standard thermometers. The advantage of this satellite scanning is its ability to cover entire urban areas uniformly.
The results are quite surprising. The steepest temperature increases were detected in cold-climate cities and occurred during the winter season, rather than under the summer sun. Over two decades, the fastest-warming cities experienced daytime surface temperature increases of up to 4 degrees Celsius (7 degrees Fahrenheit). This sharpest surge is centred in regions of Eastern Europe and Western Asia.
The reason why cold cities are warming faster is not yet fully certain. However, the loss of winter snow, which previously functioned to reflect sunlight, along with rapid infrastructure development, are strongly suspected to be the triggers.
While peak daytime temperatures often make headlines, extreme heat actually has the most damaging impact at night. In arid cities, the frequency of hot nights has surged by approximately 47 per cent compared to the start of the data recording.
Cool nights are ideally a time for the human body to recover after a day of heat exposure. When that opportunity is lost, physical strain continues to accumulate, increasing the risk of sleep disturbances, severe heat exhaustion, and heavier cardiac workloads, particularly for the elderly.
Globally, the combination of rising temperatures and urban population growth has increased exposure to extreme heat in urban areas by 51% worldwide.
Through the study published in the journal Communications Earth & Environment, the research team successfully isolated these driving factors. In continental regions with freezing winters, climate change is the primary driver, accounting for a 71% increase in daytime heat exposure. Conversely, in arid cities, dense population growth is the more dominant driver, contributing 69% to the increase.