Abstract：An analysis on the Report of OSD (Office of Security Department) is made. The report suggests that gradual global warming will bring chilling. It is indicated that the chilling had occurred many times in the past, for the warming melt ice cover, modulated the thermohaline circulation, and finally influenced on the global climate. However, it is premature to say that a new phase of chilling is coming, because no strong precursor has been found. Therefore, in the near future occurrence of the scenario suggests in the report is almost impossible. But it is difficult to exclude the possibility of occurrence of a chilling in some whatlonger time, so it is necessary to increase the research on the abrupt climate change.