Time of emergence of climate signals over China under the RCP4.5 scenario

The signal of climate change is emerging against a background of natural internal variability. The time of emergence (ToE) is an indicator of the magnitude of the climate change signal relative to this background variability and may be useful for climate impact assessments. In this work, we examined the ToE of surface air temperature and precipitation over China under a medium mitigation scenario Representative Concentration Pathway 4.5 based on 30 satisfactory global climate models that are chosen from the Coupled Model Intercomparison Project Phase 5. Major conclusions are: the earliest ToE of annual and seasonal temperature occurs in the eastern Qinghai-Tibetan Plateau between 2006 and 2012 for S/N > 1.0 and between 2020 and 2030 for S/N > 2.0, which is 10-20 years sooner than in Northeast China where the latest ToE appears in the country. Consistent with previous studies at the global scale, the median ToE for most of China occurs sooner in summer (2008-2020 for S/N > 1.0 and 2020-2045 for S/N > 2.0), while for Northeast and North China the median ToE occurs sooner in autumn (2015-2025 for S/N > 1.0 and 2040-2050 for S/N > 2.0). For the ToE of temperature, the inter-model uncertainty is at least 24 years in all five regions of concern and more than 85 years in some seasons, and the inter-model uncertainty in one season for which the earliest median ToE occurs is the smallest among the seasons. For precipitation, the early ToE occurs in the northeastern Qinghai-Tibetan Plateau for the annual mean, and seasonally it occurs first in winter in northern Northeast China and southwestern Northwest China and in winter and spring in the northeastern Qinghai-Tibetan Plateau. For southern China, the median ToE will not occur until 2090.