Research projects

Research projects future mortality burden from hot nights

Excessively hot nights caused by climate change are expected to increase the global death rate by up to 60% by the end of the century, according to a new international study that features research from the UNC Gillings School of Global Public Health .

Ambient heat at night can disrupt normal sleep physiology. Less sleep can then lead to damage to the immune system and a higher risk of cardiovascular disease, chronic diseases, inflammation and mental health problems. The results show that the average intensity of hot night events will almost double by 2090 from 20.4℃ (68.7℉) to 39.7℃ (103.5℉) in 28 cities in South Asia. ‘Is increasing the disease burden due to excessive heat that disrupts normal sleep patterns.

This is the first study to estimate the impact of warmer nights on mortality risk from climate change. The results show that the burden of mortality could be significantly higher than predicted by the increase in mean daily temperature, suggesting that warming due to climate change could have a worrying impact, even under the restrictions of the Accord. of Paris on the climate.

The risks of temperature rises at night have often been overlooked. However, in our study, we found that occurrences of nocturnal hot excesses (HNE) are expected to occur faster than average daily temperature changes. The frequency and average intensity of hot nights would increase by more than 30% and 60% by the 2100s, respectively, compared to less than 20% increase for the average daily temperature. »

Yuqiang Zhang PhD, study co-author and climatologist, Department of Environmental Science and Engineering, Gillings School of Global Public Health

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

Using this model, the team was able to estimate that between 2016 and 2100, the risk of death from excessively hot nights would increase almost sixfold. This prediction is much higher than the mortality risk from average daily warming suggested by climate change models.

“Based on our study, we emphasize that when assessing the burden of disease due to suboptimal temperature, governments and local decision-makers should consider the additional health impacts of disproportionate intra-temperature variations. A more comprehensive assessment of the health risks of future climate change can help policymakers better allocate resources and set priorities,” said Haidong Kan, PhD, a professor at Fudan University in China and author study correspondent.

In this study, the authors also found that regional temperature differences explained many of the overnight temperature departures, and that areas with the lowest average temperature would have the greatest warming potential.

“To combat the health risk raised by temperature rise due to climate change, we need to devise effective ways to help people adapt,” Zhang said. “Locally, the 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 expenses of In addition, stronger mitigation strategies, including global collaborations, should be considered to reduce future impacts of warming.”

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


Journal reference:

Him, C. et al. (2022) The effects of overnight warming on mortality burden under future climate change scenarios: a modeling study. The Planetary Health of the Lancet.