Trends in adaptability to heat and cold in a cooling climate, 1994-2013

Numerous studies have indicated that adaptability of population to warmer temperatures changes with global warming. However, population adaptability to gradually decreasing temperatures has seldom been reported. Our objective was to investigate the changing population adaptability to non-optimum temperatures in Northeast China from 1994 to 2013, when the ambient temperature showed a downward trend, addressing two aspects: heat- and cold-related mortality risks and minimum mortality temperature (MMT). To analyze the differences in the nonlinear and delayed effects of temperature-mortality relationships, a distributed lag nonlinear model was applied. MMT and heat- and cold-related mortality risks were calculated. The temperature in Shenyang showed a significant downward trend from 1994 to 2013, with an average decrease of 0.7(degrees)C in 10 years. We found strong evidence of decreasing cold- risk and increasing heat- risk over time. MMT of respiratory death showed a downward trend. However, there was no significant change in MMT of circulatory system and total death. The overall impact of air temperature on mortality shows a downward trend. Our findings offer insights into adaptability to the adverse effects of temperature changes and add new evidence that people could adapt to changes in ambient temperature whether increases or decreases.