מחקר עולמי חדש: עלייה מסוכנת בחום בשעות הלילה ב-83% מערי העולם שנותחו, הופך למעיק יותר ותכוף יותר

וושינגטון, 19 בנובמבר 2025 (GLOBE NEWSWIRE) –

בעוד שמנהיגים התמקדו במניעת חציית סף ה-1.5 מעלות הצלזיוס לפי הסכם פריז, ניתוח מדעי חדש ומקיף של תנאי מזג האוויר המסוכנים ביותר בקיץ ב-100 ערים גדולות ברחבי העולם גילה כי טמפרטורות הלילה המינימליות עלו עד פי 10 מהר יותר מהשיא הממוצע בשעות היום בערים רבות ברחבי העולם במהלך מזג אוויר מעיק וחם במיוחד.

המחקר של Climate Resilience for All "חום קיצוני והקטנת טווח היום: הערכה עולמית של אופי ותדירות מסת האוויר המדכאת", ניתח נתוני מזג אוויר במשך תקופה של 30 שנה בין 1994 ל-2024, ובודד את שני סוגי תנאי מזג האוויר, או "מסות אוויר", הנחשבות למסוכנות ביותר לבריאות האדם: מזג אוויר טרופי יבש (DT), שהוא חם ויבש, ומזג אוויר "טרופי לח" (MT) שהוא חם ולח.

New Global Study: Dangerous Nighttime Heat Rising in 83% of Global Cities Analyzed, Becoming More Oppressive, And More Frequent

WASHINGTON, Nov. 19, 2025 (GLOBE NEWSWIRE) –

While leaders have been focusing on avoiding breaching the +1.5°C threshold of the Paris Agreement, a sweeping new scientific analysis of the most dangerous summer weather conditions across 100 major global cities revealed that minimum nighttime temperatures have been rising up to 10 times faster than daytime average highs in many global cities during oppressively hot weather.

The study by Climate Resilience for All, Extreme Heat and the Shrinking Diurnal Range: A Global Evaluation of Oppressive Air Mass Character and Frequency, analyzed weather data over a 30-year period from 1994 to 2024, isolating the two types of weather conditions, or “air masses”, considered most dangerous for human health: “dry tropical” (DT) weather, which is hot and dry, and “moist tropical” (MT) weather which is hot and humid.

Heat exposure has traditionally been measured by exposure to daytime high temperatures and increasing “average” temperatures. This study points clearly to the urgent need for preventative and responsive actions on extreme heat to explicitly account for and address the rapidly rising threat of hotter nights.

Global, regional, and city level data visualizations can be accessed via this link.

The analysis found:

Increases in nighttime temperatures, and decreases in the gap between daytime highs and nighttime lows across much of the globe

• 83% of cities in the study areexperiencing sustained, higher nighttime temperatures.
• Nighttime temperaturesare rising fastest in Melbourne, Australia (dry tropical), where theyincrease by 1°C every 5.36 years, and Dubai, UAE (moist tropical), wherethey rise by 1°C every 8.81 years.
  • During moisttropical weather, Santa Maria, Upington, Seoul, Samarkand,Paris, Kuwait City, Portland, and Abadan are seeing the biggest decreasebetween daytime and nighttime temperatures. The number of cities seeingdecreases per region breaks down as follows:
    • Africa: 13 out of15.
    • Asia: 18 out of 22.
    • Central and SouthAmerica: 10 out of 11.
    • Europe: Seven out of12.
    • Middle East: 5 outof 5.
    • North America: 14out of 16.
    • Oceania: Nine out of11.
  • During drytropical weather, Melbourne, Agadir, Seoul, Mumbai, Cairo,Luxor, Kuwait City, and Santiago are seeing the biggest decrease betweendaytime and nighttime temperatures. The number of cities seeing decreasesper region breaks down as follows:
    • Africa: 10 out of14.
    • Asia: 13 out of 22.
    • Central and SouthAmerica: Seven out of 11.
    • Europe: Four out ofsix.
    • Middle East: Six outof seven.
    • North Americas: 11out of 14
    • Oceania: Five out ofnine.
    • Some of the regionsshow weaker differentiation, possibly because dry tropical weather typesare rarely present in the cities we evaluated in those regions.

Increases in the frequency of extreme heat days

• Over the 30-year studyperiod, summertime moist tropical weather patterns haveincreased close to or over 50 percent in Central and South America,Oceania, and Africa - and have grown by 37 percent globally.
• Dry tropical weather patternshave grown by 13 percent over the same period, with the largest increasein Australia, which had a 29 percent rise.

“Before this analysis, we did not know how rapidly nighttime heat has been rising within the most dangerous air masses,” said Larry Kalkstein, climatologist, Chief Heat Science Advisor at Climate Resilience for All, and the study's lead author. “It is critical for us to understand how the heat of summer—that sends people to the emergency room—is shifting, and what we are overlooking when we talk about it.”

“We want this analysis to mobilize city and health leaders to urgently broaden their view of what is a 24-hour heat crisis. This research uncovers a critical blind spot in our understanding of extreme heat,” said Kathy Baughman McLeod, CEO of Climate Resilience for All.

High nighttime temperatures prevent the human body from cooling down, increasing risks of heat exhaustion, dehydration, and cardiovascular stress. When sleep is disrupted by heat, the body loses its ability to recover from daytime exposure, heightening the danger of illness and death—especially for older adults, women, and those living in poorly ventilated housing.

Heat warning systems are focused on high daytime temperatures and currently minimize the impact of overnight temperatures. The study offers guidance and urges health officials and policymakers to integrate these changing patterns into their work and to ramp up regionally targeted heat warning systems that account for the growing probability of multi-day, high-intensity events that offer little nocturnal relief.

About Climate Resilience for All

Climate Resilience for All is a global adaptation NGO dedicated to protecting the health, income, and dignity of women on the frontlines of extreme heat.

Contacts:

Geraldine Henrich-Koenis, [email protected]

Kelechukwu Iruoma, [email protected]

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