在地质历史时期,地球的气候不断在变化,全球大气CO2浓度也在变化,二者之间是否存在一种响应—反馈作用,目前存在争议较大.本研究从地质时间尺度、千年以来和现代气候变化3个角度进行介绍,认为全球气候变化是多重时间尺度变化规律的叠加,从长时间尺度来看,全球平均温度和大气CO2水平均表现出整体降低的趋势.地质历史时期存在多次大气CO2浓度升高的时期,有时甚至可达现在大气CO2水平的十几倍.气候变化与大气CO2的关系非常复杂,高CO2时期并不全部对应于高温时期.千年以来的气候变化在全球各大洲均有温暖时期的出现,并且很多地方的重建结果表明中世纪暖期的全球平均温度要比现代的全球平均温度还高.但这一区间的温度变化和大气CO2水平在1850年之前没有明显的相关性.近百年的气候观测资料表明全球平均温度上升了0.74℃,但对于这种上升的理解目前还存在较大争议.是否确实是由于人类活动（主要是工业革命以来）导致了全球CO2水平增高,进而导致全球变暖,需要更多的证据来验证.%In geological history, the earth＇s climate changed regularly and constantly and the concen- tration of atmospheric CO2 ~dso changed over time, so scientists argue whether there were response- feedback effects between them. In this paper, global climate change is assumed to be a multiple time- scale change, various time scales including long time orbital-scale, thousand year time-scale and nearly hundred years are introduced and analyzed. For long time-scale, both average global tempera- ture and atmospheric CO2 level present a reduction trend. Many times during geological history, at- mospheric CO2 level rose, sometimes to as high as ten times of the present level. It is found that the high C02 level period was not always corresponding to the high temperature period. For thousand year time-scale, it is found that ＇warm periods emerged at all global continents, for instance, the tempera- ture in medieval period was even higher than that of today. During the past one hundred year, the average global temperature rose by O. 74 ℃, and there are different understandings about the reason. It is too early to say that the global warming since the industrial revolution was mainly caused by human activities. Further investigation are required.
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