Assessing the Regional Impacts of Climate Change on Grain Yield and Nitrogen Surplus in China (2000–2020)

Rising food demand and nitrogen pollution have posed key challenges under climate change. This study analyzed meteorological and grain yield data from 2000 to 2020 across seven regions in China. By integrating an economic–climate model with a nutrient balance approach, it examined the effects of climate change on yields and nitrogen surplus. During the study period, average temperatures rose in all regions (0.73–1.49 °C), with more pronounced warming in northern areas. Rainfall trends varied regionally, from a decrease of 159.76 mm to an increase of 179.93 mm. Despite these climatic changes, national grain yields increased from 390 million tons in 2000 to 600 million tons in 2020, with temperature having a stronger influence on yield variation than rainfall. Nitrogen surplus showed regional differences, ranging from −236.50 kg·hm−2 to 117.20 kg·hm−2. In most areas, temperature and nitrogen surplus were negatively correlated. In contrast, rainfall had a weaker effect, with positive and negative coefficients close to zero. These results provide a basis for promoting green agricultural development in China.