Human-induced climate change has more than doubled the number of dangerous humid heat days recorded across the world since the 1970s, exposing hundreds of millions of people, including Nigerians, to heightened risks of heat-related illnesses and death, a new report has revealed.
The analysis, released on Wednesday by a US-based independent group of scientists and communicators under the aegis of Climate Central, found that dangerous humid heat days increased globally from an average of 10 days annually in the 1970s to 23 days per year between 2016 and 2025, with climate change now accounting for nearly two-thirds of such extreme conditions worldwide.
The report warned that rising temperatures driven largely by the continued burning of fossil fuels are making dangerous heat more frequent, intense, and widespread, particularly in regions already vulnerable to extreme weather.
The findings come as Nigeria continues to experience increasingly prolonged heatwaves, with health experts raising concerns over growing cases of heat exhaustion, dehydration, and other heat-related illnesses across several parts of the country.
“Climate change is now responsible for six times as many dangerous humid heat days annually compared to the 1970s.
“In 2025 alone, the world recorded an average of 23 dangerous humid heat days, of which 19 days representing 83 per cent were directly linked to human-caused climate change.
“Researchers analysed weather records from 1970 to 2025 using wet-bulb temperature, an internationally recognised measure that combines heat and humidity to determine how stressful weather conditions are on the human body,” the report stated.
The study classified wet-bulb temperatures of 25 degrees Celsius or higher as dangerous because such conditions significantly reduce the body’s ability to cool itself through sweating.
The report also stated that climate change has increased dangerous humid heat days in 69 per cent of the 961 cities analysed globally, adding an average of 46 additional dangerous heat days annually over the past decade.
“Humidity greatly amplifies the health risks associated with high temperatures because it limits the evaporation of sweat, the body’s primary cooling mechanism.
“As a result, people become more susceptible to dehydration, heat exhaustion, heat stroke, cardiovascular complications, respiratory illnesses, and, in severe cases, death,” it stated.
Climate Central also noted that extreme heat has claimed more than 250,000 lives worldwide since 2000, making it one of the deadliest weather-related hazards globally.
The report identified older adults, children, pregnant women, people living with underlying medical conditions, and individuals without access to cooling facilities as the most vulnerable groups.
Commenting on the findings, Clinical Associate Professor of Pediatrics at Stanford Children’s Health and Executive Director of the Medical Society Consortium on Climate and Health, Dr Lisa Patel, described the trend as an urgent public health emergency.
“As a pediatrician, these numbers are a wake-up call. Dangerous humid heat has more than doubled since the 1970s. We are already seeing the consequences play out in real time,” Patel said.
She cited incidents of spectators collapsing during football matches in Houston, United States, as evidence of how rising temperatures are already affecting public health.
“This kind of data is exactly the tool clinicians and public health officials need to anticipate where heat-related illness will strike and who is most at risk before people end up in the emergency room,” she added.
Also commenting, Applied Climate Scientist at Climate Central, Kaitlyn Trudeau, said the findings demonstrate how climate change is fundamentally altering weather patterns around the world.
“These findings show how profoundly climate change is reshaping our world. Dangerous humid heat has gone from being an uncommon event to a defining feature of daily life in some regions, pushing conditions closer to the limits of what the human body can safely endure,” Trudeau said.
Although the report covered global trends, environmental and public health experts say the findings carry significant implications for Nigeria, where rising temperatures, rapid urbanisation, inadequate access to electricity, and limited cooling infrastructure increase residents’ vulnerability during extreme heat events.
Several northern states have in recent years recorded temperatures exceeding 40 degrees Celsius during the dry season, while coastal cities such as Lagos, Port Harcourt, and Warri frequently experience oppressive humidity that intensifies heat stress.
Climate experts have repeatedly warned that without stronger climate adaptation measures, improved early warning systems, and investments in resilient healthcare infrastructure, heat-related illnesses are likely to become more common across Nigeria.
The report urged governments to accelerate efforts to reduce greenhouse gas emissions, strengthen public health preparedness, and protect vulnerable populations from the growing impacts of climate change.
Researchers noted that reducing dependence on fossil fuels remains one of the most effective ways to slow the increasing frequency of dangerous humid heat events globally.
By Dare Akogun
