A GHP study was highlighted in the “10 New Insights in Climate Science 2024/2025”
Each year, Future Earth, The Earth League, and the World Climate Research Programme gather leading scholars from around the world to review the most pressing findings in climate change research. The result is the 10 New Insights in Climate Science, a policy report providing a rich and valuable synthesis for policymakers and society at large.
Recently, these organizations released the “10 New Insights in Climate Science” for 2024/2025. A GHP study, titled “Net Impact of Air Conditioning on Heat-Related Mortality in Japanese Cities”, was highlighted as the primary reference for Insight 8, “New frameworks for climate-resilient development in cities provide decision-makers with ideas for unlocking co-benefits.”
This study is a collaborative effort by the University of Tokyo, the National Institute of Advanced Industrial Science and Technology (AIST), and the National Institute for Environmental Studies (NIES). Prof. Paul L.C. Chua, Assistant Professor at GHP, is the lead author, with collaborators including Prof. Masahiro Hashizume, Prof. Yoonhee Kim, Prof. Chris F.S. Ng, Dr. Yuya Takane (AIST), Dr. Kazutaka Oka (NIES), and Prof. Yasushi Honda (NIES).
The short introduction of the study is as follows:
Background
Air conditioning (AC) presents a viable means of tackling the ill-effects of heat on human health. However, AC releases additional anthropogenic heat outdoors, and this could be detrimental to human health, especially in urban communities. This study determined the excess heat-related mortality attributable to anthropogenic heat from AC use under various projected global warming scenarios in seven Japanese cities. The overall protection from AC use was also measured.
Methods
Daily average 2-meter temperatures in the hottest month of August from 2000 to 2010 were modeled using the Weather Research and Forecasting (WRF) model with BEP+BEM (building effect parameterization and building energy model). Risk functions for heat–mortality associations were generated with and without AC use from a two-stage time series analysis. We coupled simulated August temperatures and heat–mortality risk functions to estimate averted deaths and unavoidable deaths from AC use.
Results
Anthropogenic heat from AC use slightly augmented the daily urban temperatures by 0.046 °C in Augusts of 2000–2010 and up to 0.181 °C in a future with 3 °C urban warming. This temperature rise was attributable to 3.1–3.5 % of heat-related deaths in Augusts of 2000–2010 under various urban warming scenarios. About 36–47 % of heat-related deaths could be averted by air conditioning use under various urban warming scenarios.
Discussion
AC has a valuable protective effect from heat despite some unavoidable mortality from anthropogenic heat release. Overall, the use of AC as a major adaptive strategy requires careful consideration.
Journal article: Chua, P.L.C., Takane, Y., Ng, C.F.S., Oka, K., Honda, Y., Kim, Y., and Hashizume, M. (2023). Net impact of air conditioning on heat-related mortality in Japanese cities. Environment International 181, 108310. https://doi.org/10.1016/j.envint.2023.108310.