A recent study co-led by City University of Hong Kong (CityUHK) found that strong El Niño events cause deeper, longer-lasting harm to human health than previously understood—by slowing long-term improvements in mortality rates for many years, shortening life expectancy, and generating major economic costs. Even in relatively wealthy, well-resourced countries and regions, each major El Niño event can stall improvements in life expectancy that people would otherwise have enjoyed.
The study, titled “ Enduring impacts of El Niño on life expectancy in past and future climates ”, jointly led by Professor Benjamin Horton , Dean of the School of Energy and Environment at CityUHK and a research team from Nanyang Technological University in Singapore, was published in the leading journal Nature Climate Change .
The study analysed data spanning six decades across 10 Pacific Rim countries and regions, including Australia, Japan, the USA, Singapore and Hong Kong. Their findings revealed that El Niño events threaten human health by increasing mortality during the event years.
El Niño events involve fluctuations between unusually warm (El Niño) and cold (La Niña) sea surface temperatures in the central and eastern Pacific Ocean, which trigger extreme weather conditions globally, such as floods, heatwaves and air pollution. These extreme weather conditions disrupt food security, hinder economic growth and affect multiple regions worldwide.
The study highlights that these effects impact multiple health domains, such as infectious and diarrhoeal diseases, cardiovascular and respiratory conditions, and disruptions to healthcare systems. Vulnerable populations, such as children and the elderly, face heightened risks, with El Niño events contributing to excess mortality.
It found that the two strongest events, in 1982–83 and 1997–98, reduced life expectancy by approximately half a year and one-third of a year, respectively, while causing economic losses estimated at US$2.6 trillion and US$4.7 trillion.
According to the study, the impact on life expectancy specifically in Hong Kong from these two largest El Niño events was close to the average observed across the 10 Pacific Rim countries. In terms of financial losses, the estimated impact of the 1982–83 event in Hong Kong was approximately 0.6 years of reduced life expectancy, equivalent to an economic loss of approximately US$15 billion for the total population. For the 1997–98 event, the estimated impact on life expectancy was about 0.4 years, corresponding to an economic loss of approximately US$58 billion for the total population.
Professor Horton explained that although the study does not provide direct country- or region-level future projections, apportioning losses by population and economic size suggests that Hong Kong could face cumulative economic losses of US$250–300 billion over the 21st century from the effects of El Niño. He added that intensifying El Niño events may reduce life expectancy by 2.8 years across the regions studied, resulting in economic losses of up to US$35 trillion by 2100.
“El Niño is predictable,” Professor Horton emphasised. “So, with the right planning, we can reduce its impacts. To mitigate El Niño events, countries and regions need strong early-warning systems, heat-health action plans, better water management, and protection for workers exposed to extreme heat. They also need resilient infrastructure, smarter agriculture that can cope with heatwaves, droughts and heavy rainfall, and public health systems that are prepared for spikes in disease and pollution.”
Nature Climate Change
Data/statistical analysis
Not applicable
Enduring impacts of El Niño on life expectancy in past and future climates
9-Jan-2026
The authors declare that they have no competing interests.