Hot Nights Lead to higher Mortality Rate

Hot Nights Could Lead to higher Mortality Rate

It is not a false statement if one should say that climate change leads to death. More, mortality rates could go up by 60 per cent by the end of the century due to hot nights because of climate change.

This comes up in a new study that features research from the UNC Gillings School of Global Public Health.


An increased heat during night interrupts normal physiology of sleep. The researchers point out that less sleep could lead to immune system damage and a higher risk of cardiovascular disease, chronic illnesses, inflammation and mental health conditions.

As per the calculations of the researchers, average intensity of hot night events would nearly double by 2090, from 20.4℃ (68.7℉) to 39.7℃ (103.5℉) across 28 cities.


The researchers claim this as the first study to estimate the impact of hotter nights on climate change-related mortality risk. The study shows that the burden of mortality could be significantly higher than estimated by average daily temperature increase. This suggested that warming from climate change could have troubling adverse impact, even under restrictions from the Paris Climate Agreement.

Study co-author Yuqiang Zhang said that the occurrences of hot night excess (HNE) are projected to occur more rapidly than the daily mean temperature changes. “The frequency and mean intensity of hot nights would increase more than 30% and 60% by the 2100s, respectively, compared with less than 20% increase for the daily mean temperature,” the researcher said.  

Zhang is a climate scientist in the Department of Environmental Sciences and Engineering at the Gillings School.

The study, published in The Lancet Planetary Health, was co-authored by a group of researchers in China, South Korea, Japan, Germany and the United States. The team estimated the mortality due to excess heat in 28 cities in China, South Korea and Japan between 1980 and 2015 and applied it to two climate change modeling scenarios that aligned with carbon-reduction scenarios adapted by the respective national governments.

 Through this model, the team concluded that between 2016 and 2100, the risk of death from excessively hot nights would increase nearly six-fold. This prediction is much higher than the mortality risk from daily average warming suggested by climate change models.


Haidong Kan, who is a professor at Fudan University in China and the study’s corresponding author, said governments and local policymakers should consider the extra health impacts of the disproportional intra-day temperature variations. “A more complete health risk assessment of future climate change can help policymakers for better resource allocation and priority setting,” the author said.

Zhang opined that the authorities and stakeholders should design efficient ways to help people adapt to the climate change. “Locally, heat during the night should be taken into account when designing the future heat wave warning system, especially for vulnerable populations and low-income communities who may not be able to afford the additional expense of air conditioning. Also, stronger mitigation strategies, including global collaborations, should be considered to reduce future impacts of warming,” the researcher said.

Since the study only included 28 cities from three countries, Zhang said, “Extrapolation of these results to the whole East Asia region or other regions should be cautious. Currently, based on these findings, authors are trying to extend the analysis to a global dataset. Then we could have a global picture of the deadly nighttime heat on health under climate change scenarios.”


Latest studies point out that nights are warming more and faster than days. This means that the warm nights deprive the bodies and minds of the chance to cool off, which has adverse impact on the health.

In a study published in the journal One Earth, the researchers found that increased night time temperature led to less sleep. The study noted that the situation could only become worse in coming years. The study found that right now people are already losing an estimated 45 hours of sleep per year due to hotter nighttime temperatures.


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