Agriculture changes natural vegetation and therefore water and energy exchanges between land and atmosphere.This may cause different impacts on regional climates,depending on the different climates themselves.We compare the impacts of agriculture on July climate between the Little Ice Age(LIA)and the present warm period through numerical modeling with global and regional climate models.The cooling in northern China in the LIA is about -1 3℃ lower than the present.Agriculture tends to ameliorate the large scale cooling(from -1.3℃ to -0.8℃).Agriculture causes widespread decreases in precipitation in eastern China in the LIA,but not under modern conditions.The different land surface energy balances induced by agriculture in different periods are discussed to explain the different climate effects of agriculture.