关键词: 关键词：新生代气候;温室气体;碳循环;人类活动

Abstract:

Abstract:  Based on the available data, earlier studies and our own recent results, in this paper we discuss the potential links between the Cenozoic climate changes and the atmospheric concentrations of greenhouse gases at the tectonic, orbital and millennial timescales with special emphasis given to CO2. The comparisons show a generally coupling between them, indicating that the greenhouse gases are among the most prominent driving forces of the climate system. However, a significant amount of decoupled aspects is also clear. These include the longterm global cooling and ice volume increase during the Neogene under relatively stable CO2 concentrations, the strong asymmetry of hemispheric climates at the glacialinterglacial scale during the midPleistocene, and the seesaw pattern between the Southern and Northern Hemispheres at millennial scales. Also, most of the studies showed that the  change in the CO2 concentration at the orbital and millennial scales lagged the change of the global temperature, which suggested that the changes in the CO2 concentration at these timescales were likely induced by climate changes, but may have a significant feedback of CO2 to climate conditions in modulating the amplitudes of climate changes. The climateCO2 relationships during the Cenozoic are helpful for understanding the mechanisms of the ongoing global warming, but the differences in the boundary conditions between the geological past and the presentday must be taken into consideration. Climate and greenhouse gases may be, to some extent, a selfmodulated system while little is known about the relevant processes. Datamodel comparisons would be of great value towards understanding these links.

Key words: Key words: Cenozoic climate; greenhouse gas; carbon cycle; human activity