最高和最低温度的变化对农业和环境的影响比平均温度更加重要。自20世纪50年代以来,中国北方最高和最低温度变化的特点是:最低温度升温速率大于最高温度的升温速率;冬季升温速率大于夏季;偏北(纬度较高)地区的升温速率大于偏南(纬度较低)地区。黄淮海和西北区,夏季最高气温呈下降趋势。对最高和最低温度变化作突变性检验,年平均最高气温变化的突变点发生于1992年,年平均最低温度变化的突变点发生于1981年。最低温度明显升高的年份远远早于最高气温,这说明最低气温的变化比最高气温变化敏感,中国北方气候变暖主要来自于最低温度升高的贡献。自20世纪80年代气候变暖以来,中国北方喜温作物种植面积扩大,作物种植北界向北推移。

Since the second half of the 20th century,many researchers at home and abroad have studied global temperatures rising and its impacts on crops and environment.But most of the studies have been only limited to the change of mean temperature.For the terrestrial ecosystem, the daily maximum temperature is the important factor determining the normal photosynthetic mechanism control,fruit quality and glaciers melting.Moreover,the minimum temperature at night is important for crop respiration,dry material accumulation,and crops overwintering.Therefore, changes of the maximum and minimum temperatures are more important than the mean temperature in terms of their impacts on environment and physiological activities of plants.In terms of the seasons,the rising rate of temperature in winter is higher than that in summer.In terms of regions,the rising rate of temperature in the northern part of northern China is higher than that in the southern part of northern China.The maximum temperature in summer tends to decline in Huang-Huai-Hai plain.In terms of the temperature types,the rising rate of the minimum temperature is higher than that of the maximum temperature.A sudden change test was made for the maximum and minimum temperature of northern China by using Mann-Kendall climate sudden change statistics check method.The results show that the sudden change point of annual mean maximum temperature was in 1992,and the temperature evident rising occurred in 1994.The evident rising of annual mean minimum temperature occurred in 1981,and the time of the occurrence in sudden change point of minimum temperature is far prior to that of maximum temperature.These facts indicate that the change of the minimum temperature is more sensitive than that of the maximum temperature.It is concluded that the main contributor of climate warming in northern China is the rising of the minimum temperature.Meanwhile,since the occurrence of global evident warming in the 1980s, the growing area of thermophilic crops in northern China has been expanded and the north limit of crops cultivation has been shifted northward.