MANILA — Climate change is no longer disrupting lives only through stronger typhoons, floods, or searing daytime temperatures.
Scientists are now warning that rising nighttime temperatures are quietly robbing millions of people of one of the body's most essential defenses against illness -- sufficient quality sleep.
The finding comes from a new analysis by Climate Central on July 15, 2026, which estimated that the average person worldwide lost more than 50 hours of sleep each year between 2020 and 2025 because climate change increased nighttime temperatures.
The report adds to growing scientific evidence that warmer nights are becoming a public health concern, with implications that go beyond discomfort.
Poor sleep has been linked to weakened immunity, slower recovery from illness, reduced productivity, impaired cognitive function, and even higher risks of premature death.
"Hot nights make it harder for people to recover from the heat of the day, with wide-reaching and severe consequences. There is growing evidence that as nighttime temperatures rise, human sleep is being eroded around the world," Climate Central said.
Unlike daytime heat, nighttime temperatures are supposed to provide the body with an opportunity to cool down and recover. But scientists say climate change is shrinking that window of recovery.
Climate Central found that across Southeast Asia, climate change added at least 40 nights annually of warmer nighttime temperature, when minimum temperatures remained above 25 degrees Celsius or conditions considered uncomfortable for sleeping.
Although the analysis focused on selected locations in the United States, the United Kingdom, and India, experts say the findings are highly relevant to the Philippines, where rising temperatures, rapid urbanization, and the urban heat island effect have made nights increasingly warmer.
NIGHTS NO LONGER COOLING DOWN
The findings echo a recently launched Greenpeace Philippines report, "Here Comes the Sun," which found that higher average temperatures are preventing nighttime conditions from serving as the "thermal break" people need after prolonged daytime heat.
"This reduces the body's chances to recover from extreme daytime temperatures," the report said.
Speaking to ABS-CBN News, Jefferson Chua, campaigner for Greenpeace Philippines, said the global findings reinforce what has already been observed locally.
"What is alarming is that the body is losing one of its most effective recovery mechanisms," he said.
"We know that sleep is the single best recovery mechanism for the body. So if you take that out, you're taking away the resilience aspect of human body. We're also seeing the links between less cell regeneration and loss of sleep. So, ibig sabihin nito, mas matagal nagre-recover yung mga tao kapag may mga sakit sila.”
Scientists say sleep is essential for regulating hormones, repairing tissues, strengthening the immune system and maintaining cardiovascular and mental health. Chronic sleep deprivation has also been associated with diabetes, hypertension, depression, and reduced work performance.
According to Chua, the effects extend beyond individual health and could eventually affect the country's economy.
Global estimates already suggest that extreme heat affects nearly half of the formal workforce.
"These cover just the formal workforce. So what we are expecting is really the worst case scenario na mas madami ang naapektuhan.”
WHY ARE NIGHTS BECOMING HOTTER?
Experts say the impacts of extreme heat do not end after sunset.
In densely built cities such as Metro Manila, concrete roads, buildings, glass, and asphalt absorb large amounts of heat throughout the day. Instead of quickly cooling after sunset, these materials slowly release the stored heat, keeping nighttime temperatures elevated, a phenomenon known as the urban heat island effect.
Dr. Rosa Perez, fellow at the Manila Observatory and the National Resilience Council, said weather conditions and greenhouse gases further intensify the problem.
Cloudy skies can prevent accumulated heat from escaping into space, while greenhouse gases trap heat within the atmosphere.
"Ang gases like carbon dioxide, methane, ang chemical structure nila, loose. So, may mga spaces in between ng mga molecules and atoms. So yung heat, natatrap nila,” she said.
The World Meteorological Organization has reported that recent years have been the warmest ever recorded globally, with greenhouse gas concentrations continuing to reach record highs.
SLEEP LOSS CARRIES SERIOUS HEALTH RISKS
For Riza Torres, a vendor living in a densely populated community in Quezon City, warmer nights have made getting enough sleep increasingly difficult.
She often spends the night fanning her young children because the family's small clip fan is not enough to keep them cool.
"Ang hirap talaga lalo na pag may maliit kang anak. Kahit anong paligo mo sa kanila, maiinitan pa rin. Kaya magtitiis akong mag paypay kasi ang electric fan namin, de clip lang eh. Kaya puyat. Pero gigising ka parin kasi no choice ka eh,” Torres said.
Health experts warn that repeated nights of inadequate sleep, combined with prolonged exposure to extreme heat, can have lasting consequences.
In children, insufficient sleep may impair brain development, learning, concentration, and memory. Among workers, fatigue increases the risk of workplace injuries and accidents while reducing productivity and decision-making.
Emerging research also suggests that hotter nights may increase the risk of death.
A study published in The Lancet Planetary Health found that periods of hot night excess (HNE) were significantly associated with higher mortality.
"The relative mortality risk on days with hot nights could be 50% higher than on days with non-hot nights," the researchers reported.
CLIMATE AND PUBLIC HEALTH ISSUE
For Greenpeace Philippines, the growing body of scientific evidence shows that rising nighttime temperatures should no longer be viewed merely as an inconvenience, but as an emerging public health challenge driven by human-induced climate change.
Chua said the findings underscore the need for stronger climate adaptation measures, particularly for communities most exposed to extreme heat.
"I think it's also a challenge to national government to really enact climate justice policies na hindi lang napoprotektahan lahat ng Pilipino pero yung mga pinaka-vulnerable in the front lines of the climate crisis are protected first.”
As climate change continues to raise temperatures, scientists say protecting people from extreme heat is no longer just about staying cool during the day. It also means ensuring that nights remain cool enough in order for the body to adequately recover.