The study authors found that regional differences in temperature accounted for many of the variances in nighttime temperature.
Excessive heat during the night may interrupt the normal physiology of sleep and have a predicted climate-change related mortality risk on a global scale, according to the authors of a study from the UNC Gillings School of Public Health.
Less sleep due to heat can lead to immune system damage and a higher risk of cardiovascular disease, chronic illnesses, inflammation, and mental health conditions. Additionally, results showed that the average intensity of hot night events will nearly double by 2090 across 28 cities in east Asia, which will increase the burden of disease due to excessive heat that can disrupt normal sleeping patterns.
The findings of the study also demonstrated that the burden of mortality could be significantly higher than previously estimated due to the lack of consideration regarding the impact of average daily temperature increases on mortality estimates.
“The risks of increasing temperature at night were frequently neglected,” said study co-author Yuqiang Zhang, PhD, a climate scientist in the Department of Environmental Sciences and Engineering at the Gillings School, in a press release. “However, in our study, we found 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.”
During the study, the research team estimated mortality rates due to excess heat in 28 cities in China, South Korea, and Japan between 1980 and 2015 and applied it to 2 climate change modeling scenarios that aligned with carbon-reduction models adapted by each city’s respective national government.
Between the years 2016 and 2100, the team estimated the risk of death from excessively hot nights increased nearly 6-fold.
“From our study, we highlight that, in assessing the disease burden due to non-optimum temperature, 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,” corresponding study author Haidong Kan, PhD, a professor at Fudan University in China, said in the press release.
Further, the study authors found that regional differences in temperature accounted for many of the variances in nighttime temperature, and areas with the lowest average temperature were projected to have the largest warming potential.
“To combat the health risk raised by the temperature increases from climate change, we should design efficient ways to help people adapt,” Zhang said in the press release. “Locally, heat during the night should be taken into account when designing the future heatwave 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.”
Risk of death rises as climate change causes nighttime temperatures to climb. UNC Gillings School of Global Public Health; August 8, 2022. Accessed August 9, 2022. https://sph.unc.edu/sph-news/risk-of-death-rises-as-climate-change-causes-nighttime-temperatures-to-climb/