2025
Health Foresight 03
Intense and extended heat waves hit every continent in 2024, amid record-high temperatures driven by human-caused climate change and El Niño weather cycle. At least ten countries recorded temperatures of over 50°C (122°F) in more than one location. The colder phase of the El Niño–Southern Oscillation (ENSO), La Niña, is expected to emerge and persist through January-March 2025, before a return to ENSO-neutral conditions.
Although La Niña is known to cool temperatures, more extreme weather events can be expected amid rising global temperatures.
Exposure to heat can worsen pre-existing cardiovascular and respiratory conditions and cause heat exhaustion and heatstroke. Approximately 489,000 heat-related deaths occur each year, with 45 percent of these in Asia and 36 percent in Europe.
Both La Niña and the ENSO-neutral phase are associated with above-average levels of Atlantic Hurricane activity, exacerbated by record-warm ocean surface temperatures. La Niña also increases the risk of flooding including in Southeast Asia and eastern Australia. Frequent storms and flooding will exacerbate the spread of diseases, including dengue, malaria and cholera.
La Niña event of 2020-2023 contributed to consecutive seasonal droughts in parts of the United States, the Southern Cone and Brazil, and the Horn of Africa. Prolonged droughts can reduce flows in rivers and streams and concentrate pollutants, worsening the quality of water. A severe drought in much of Zambia, Zimbabwe, Malawi, Namibia, Angola, Botswana, Lesotho, Mozambique, South Africa and Madagascar caused water scarcity and food insecurity for around 30 million people in 2024. Consequently, the risk of waterborne diseases increases.
Both storms and droughts can cause power supply disruptions, potentially aggravating health conditions. Food and medicine that are required to be refrigerated can go bad during outages, while the use of electricity-dependent equipment, including air conditioning, ventilators and oxygen concentrators will not be possible, increasing hospitalisations and mortality rates.
Health conditions are also exacerbated by smoke and pollutants from drought-fueled wildfires or thermal inversion under which the air layer closest to the ground becomes more polluted. Such conditions are common during La Niña winters in cities located in valleys or near mountain ranges such as Salt Lake City, Los Angeles, Denver, Mexico City, Lahore and Delhi.
Editor: Paul Mutter
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