Two centuries of April-July temperature change in southeastern China and its influence on grain productivity.

China is a traditional agriculture based country and one main region for crop production is southeastern China where temperature is a dominant climate variable affecting agriculture. Temperature and social disturbances both influence crop production, yet distinguishing their relative impacts is difficult due to a lack of reliable, high-resolution historical climatic records before the very recent period. Here we present the first tree-ring based warm-season temperature reconstruction for southeastern China, a core region of the East Asian monsoon, for the past 227years. The reconstruction target was April-July mean temperature, and our model explained 60.6% of the observed temperature variance during 1953-2012. Spatial correlation analysis showed that the reconstruction is representative of April-July temperature change over most of eastern China. The reconstructed temperature series agrees well with China-scale (heavily weighted in eastern China) agricultural production index values quite well at decadal timescales. The impacts of social upheavals on food production, such as those in the period 1920-1949, were confirmed after climatic influences were excluded. Our study should help distinguish the influence of social disturbance and warm-season temperature on grain productivity in the core agricultural region of China during the past two centuries.