Rapid urbanisation combined with rising global temperatures is exposing billions of people to extreme heat, with new research warning that future conditions could far exceed anything experienced today. Scientists say that without urgent climate action, cities across the world will become increasingly dangerous places to live, particularly for vulnerable populations.
The study, published by researchers including Hamish Lewis and Luke Harrington, highlights how heatwaves often underestimated compared to disasters like floods or wildfires are already causing significant health impacts. These include increased deaths, hospital admissions due to heatstroke and dehydration, and worsening cardiovascular conditions.
Experts estimate that more than one-third of heat-related deaths globally can already be attributed to climate change, with risks expected to rise sharply in the coming decades as temperatures continue to climb.
Billions Could Face Unprecedented Heat By End Of Century
The research examines future scenarios based on global warming levels between 1.9°C and 3.1°C above pre-industrial levels, in line with current policy commitments under the Paris Agreement.
In a high Emissions scenario where temperatures rise by around 3.1°C, up to four billion urban residents could face extreme heat events that are currently considered rare or unprecedented, occurring as frequently as once every decade. In contrast, limiting warming to around 1.9°C could reduce the number of people exposed to such extremes to approximately one billion.
The findings suggest that every degree of warming avoided could protect around 2.5 billion people from severe heat exposure, underscoring the critical importance of climate policy decisions taken today.
Urban Growth And Inequality Intensify Heat Risks
The study also points to a growing overlap between rising temperatures and expanding urban populations. Cities are particularly vulnerable due to the “urban heat island” effect, where concrete and infrastructure trap heat, making urban areas significantly hotter than surrounding regions.
By 2050, nearly 68 per cent of the global population is expected to live in cities, up from about 55 per cent in 2018. Much of this growth will occur in regions such as South and Southeast Asia, where populations are already highly exposed to extreme heat and often lack adequate resources to adapt.
Within cities, the most vulnerable groups including the elderly, children and economically disadvantaged communities face the highest risks. Limited access to cooling, healthcare and safe housing further increases their exposure to heat-related health impacts.
Recent events highlight the growing danger. Europe’s 2022 heatwave led to more than 60,000 excess deaths, while a 2021 heatwave in Canada saw temperatures approach 50°C, resulting in hundreds of fatalities.
Urgent Climate Action Key To Reducing Future Risk
Researchers stress that the scale of future heat exposure is not predetermined but depends heavily on policy choices made now. While individuals can take steps to reduce their carbon footprint, large-scale change will require strong government action to cut emissions and implement climate-resilient urban planning.
Measures such as increasing green spaces, improving building design, and strengthening heat warning systems can help cities adapt to rising temperatures. However, experts emphasise that mitigation reducing greenhouse gas emissions remains the most effective way to limit long-term risks.
The study concludes that even small reductions in global warming could have enormous benefits, potentially sparing billions of people from life-threatening heat conditions. As cities continue to grow, the challenge of managing extreme heat is set to become one of the defining issues of the climate crisis.