活动积温是衡量一个地区农业热量资源的重要指标。在未来二氧化碳加倍的环境条件下，全球气温将明显增加，我国各地的活动积温及持续日数也将有所增加。由于目前大气环流模式只能提供具有一定可信度的月时间尺度气温变化，这给评估气候变化对活动积温及其持续日数的影响带来了一定的难度。目前评估活动积温对气候变化的响应工作均基于当前积温计算经验公式在CO2加倍情景下仍保持不变的假定上。本文应用随机模拟技术，随机生成了二氧化碳加倍前后逐日平均气温，以此方法计算活动积温与其持续日数的变化。最后讨论了积温与持续日数相关方程系数变化问题。

Accumulated temperatures and their lasting days are important indexes in agriculture. Due to doubling of CO₂ concentration in the atmosphere, temperature will increase and will result in the changes of accumulated temperatures and lasting days, We applied a stochastic simulation model for daily mean temperatures to evaluate the impacts of climate changes on accumulated temperature and correspondent lasting days. Daily meantemperatures can be decomposed in to three components. They are seasonal cycle, a sequence of several- daytime scale waves and random fluctuation. Each component can be generated stochastically by producing variousnew parameters according to their probability distributions which are obtained from daily mean temperaturerecords of many years. After three components are summed, the daily temperatures are produced. At present,GCMs only predict with some certainty changes in the monthly mean temperatures. Thus, only the monthly andyearly mean temperatures will be modified under 2×CO₂ situation.With the stochastic simulation models and scenario predicted by UKMO, 100 year daily mean temperaturesare generated in present and CO₂ doubling situations respectively. With the generated daily mean temperaturevalues, the changes of lasting days and accumulated temperature are calculated. The results show in CO₂ doublingenvironment, ≥0℃ and ≥10 ℃ accumulated temperatures and lasting days will increase with the mean monthlytemperature increase.The present correlative relationship between accumulated temperature and lasting days also will changes. Ifthis relationship is used in CO₂ doubling condition, the present corrective equations should be adjusted.