New Analysis Reveals Sharp Increase in Extreme Heat Days Across World Capitals
A new analytical report by the International Institute for Environment and Development (IIED) has revealed an alarming rise in the number of extremely hot days experienced in major world capitals, showing an increase of nearly 25% compared to the 1990s. The findings indicate that global warming is no longer a seasonal anomaly but a persistent trend reshaping urban life worldwide.
According to the report, the number of days with temperatures exceeding 35°C in 43 of the world’s most populous capitals rose from an average of 1,062 days between 1994 and 2003 to about 1,335 days during the last decade (2015–2024). This increase highlights the accelerating pace of climate change and its growing impact on urban populations.
The trend was observed across multiple continents. In Rome and Beijing, the number of extreme heat days has doubled, while in Manila the figure has tripled compared to the 1990s. In Madrid, the annual average of extremely hot days surged from 25 to 47, and even traditionally temperate cities such as London witnessed a doubling of days surpassing 30°C, a once-rare occurrence.
Researcher Anna Valentsky of IIED commented on the findings, warning that “the planet is warming at a faster rate than expected, and without urgent adaptation measures, millions of people will face life-threatening conditions—particularly in cities where the urban heat island effect magnifies extreme temperatures.”
She emphasized that the poorest and most vulnerable communities will be hit the hardest, especially in the Global South, where nearly one-third of city dwellers live in informal settlements or slums that lack proper housing, infrastructure, and cooling systems.
This warning comes as fossil fuel emissions continue to rise, despite repeated global calls to reduce them by 45% by 2030 in order to meet the Paris Climate Agreement goal of limiting global warming to 1.5°C above pre-industrial levels. Current trends, however, suggest the world is far off track, heightening the risk of severe climate consequences.
The year 2024 has already provided a stark illustration of this crisis. Record-breaking heat was documented across regions including the United States, Canada, Egypt, China, and Japan, with global temperatures peaking in July at 41.2°C. The intense heat triggered widespread health emergencies, sending more than 10,000 people to hospitals with heat-related illnesses.
In Europe, the impact proved deadly. Between June and August, a fierce heatwave claimed the lives of at least 16,500 people, most of them elderly, ill, or living in poorly ventilated housing without adequate cooling.
The report concludes with a stark message: unless governments and communities accelerate adaptation efforts, urban populations will face mounting health, social, and economic challenges. Solutions such as expanding green spaces, upgrading infrastructure, investing in renewable energy, and implementing serious carbon reduction measures are now urgent priorities if the world is to avoid catastrophic consequences in the years ahead.
