Projection of heat wave in China under global warming targets of 1.5 °C and 2 °C by the ISIMIP models

Abstract

Heat waves in China were projected under 1.5 °C and 2 °C of warming targets using the bias-adjusted simulations of 4 GCMs obtained from ISIMIP2b. The simulations of GCMs on heat wave over China during historical period of 1986–2005 were examined against daily gridded observation CN05 from National Meteorological Information Center of China. In this evaluation, three heat wave definitions respectively with absolute, relative and combined threshold were used. The results indicated that the spatial distribution of heat wave indices, including heat wave days and heat wave magnitude, could be reasonably reproduced by the simulations obtained from ISIMIP2b, and the centers over Xinjiang and Jianghuai areas could be well captured by the multi-model ensemble (MME). Among three definitions based on different thresholds, the heat wave definition based on combined threshold outperformed other two definitions with the higher correlation coefficient with observation, particularly the heat wave days (0.89) and heat wave duration (0.89). In addition, the temporal evolutions of simulated heat waves indices were generally in good agreement with observations, particular the heat wave magnitude, but with lower trend of heat wave days (0.72 days/decade) and duration (0.17 days/decade) than those in observation (1.73 days/decade and 0.41 days/decade) due to the positive bias before 1990s. The features of heat waves over China under 1.5 and 2 °C warming targets projected by the ISIMIP were explored further. The periods of 2020–2039 under RCP2.6 scenario and 2040–2059 under the RCP4.5 scenario were selected to represent the 1.5 °C and 2 °C warming targets, respectively. The MME suggested that the heat wave will increase significantly in terms of days, duration and magnitude over China. The averaged heat wave days and heat wave duration were projected to reach 10.8 days and 3.9 days under 1.5 °C warming target, which was around 1.86 and 1.56 times relative to those during historical period. Notably, the increases of heat wave were at a higher rate under 2 °C of warming target than 1.5 °C of warming target, with the heat wave days and heat wave duration were about 2.53 and 2.00 times of those during historical period. Moreover, the heat wave magnitude was projected to reach 35.2 °C and 35.4 °C, with the highest frequency fall in the range of 34.9–35.2 °C and 35.5–35.8 °C under 1.5 °C and 2 °C of warming targets, respectively.