Nighttime temperatures for around 2.4 bn people around the world were above 25°C for an extra 2 weeks annually in the past decade, according to a report (pdf) by climate science NGO Climate Central. Warmer nighttime temperatures — attributed to the continued burning of coal, oil, and gas — can harm sleep and reduce physical recovery from hot daytime temperatures, leading to cascading health impacts, chief scientist at the Laureate Institute for Brain Research Nick Obradovich told AFP.

The methodology: The analysis used models incorporating historical data to compare the annual average of hot nights between 2014 and 2023 with a hypothetical world without human-caused climate change.

Which countries were impacted the most? The Caribbean nation of Trinidad and Tobago experienced the largest increase, with an extra 47 nights per year above 25°C, while Mumbai endured an additional two months of hot nights.

The health risks are massive: Night temperatures above 25°C deteriorate sleep quality and length, increasing the risks of strokes, cardiovascular conditions, and mortality, the report said, adding that when coupled with high humidity levels, the consequences can be fatal. The elderly and low-income individuals are disproportionately affected by this phenomena, Climate Central concluded.

So what can be done? The World Health Organization (WHO) recommends keeping room temperatures at or below 24°C during the night, especially for vulnerable groups such as babies, the elderly, and those with chronic health conditions.

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