Studies on the paleoclimate during the last 20-30 years are reviewed. The following hot topics are discussed: snowball Earth and PaleoceneEocene thermal maximum (PETM), glacialinterglacial cycles, paleomonsoon, D/O cycles and H events, Holocene monsoon, abrupt climate change in the Holocene, climate change and associated ancient civilization, and the last 2 ka climate. It is indicated that, the snowball Earth and PETM were caused by the depletion and explosive increasing of CO2 in the atmosphere respectively. However, the change of temperature was preceding that of greenhouse gases in glacialinterglacial cycle, as found in the ice cores in the Antarctica. It is also shown that the changes of temperatures and greenhouse gases were highly correlated before the Quaternary, but changed after that, which might be linked to a differed mechanism. Enhancement of greenhouse effect in the present will, probably to some extent, delay the onset of the next glacial period. In any case, anthropogenic effect on the climate will definitely continue in the 21st century even we turn to reduce the emission of greenhouse gases in some ways. The global warming will remain as a critical issue, which we have to face in near future.