Projected changes in heat waves over China: Ensemble result from RegCM4 downscaling simulations.

Using the dynamical downscaling by the regional climate model RegCM4 from four global climate models, future changes in heat waves (HWs) over China under the RCP4.5 scenario are projected in terms of frequency and magnitude. The magnitude combines the duration and intensity together to characterize HW severity. The ensemble of RegCM4 downscaling simulations indicates a substantial increase in the frequency and magnitude of HWs over China toward the end of the 21st century relative to the current climate (1986–2005). The considerable changes occur in Southwest, South, North, and Northeast China for the frequency and in South, Southwest, East, and Central China for the magnitude. The prolonged HW duration plays a leading role in the enhancement of HW severity. In particular, an accelerated aggravation of the risk of extreme HWs is anticipated. Unusual HWs that never occurred in the current climate are expected to be usual phenomenon. For instance, by the end of the 21st century, the risks of the occurrence of extreme HWs (above the 99th percentile) in Southwest and South China are 64 and 53 times of the current, respectively, while the projected risks of the occurrence of mild HWs (below the 60th percentile) are much smaller and comparable in China. The HW frequency above the maximum of the current would appear once almost every year, and South, Central, and East China (North and Northeast China) would experience more severe HWs than the most extreme of the present every 1–2 (2–4) years. [ABSTRACT FROM AUTHOR]