RECENT PROGRESS ON SPECIFIC CLIMATIC STAGES AND DRIVING FORCES OVER LAST 2000 YEARS

Abstract

Temperature variations in the specific climatic periods of last 2000 years are helpful in understanding the modern climate status and its changing trend.So far four specific climatic periods have been widely identified for the period of last 2000 years,known as the Dark Ages Cold Period(DACP,400-600 AD),Medieval Warm Period(MWP,900-1400 AD),Little Ice Age(LIA,1500-1850 AD) and 20th Century Warm Period(1920s AD-present).Although there are numerous publications addressing the climate details of these periods,there remain hot debates.Studies on DACP indicate that its onset and ending time are still a matter of debate.The debate on MWP is concentrated in its geographic extent(i.e.,global or local) and its magnitude of warmth,for example,whether it was warmer than the recent decades.The debate on LIA exists with its onset and ending time,and the temperature variation in different areas.The study of the 20th Century Warm Period is focused on its driving mechanism and influencing factors.It is generally recognized that the formation of these specific climate periods may be related to a series of factors,such as solar activities,volcanic eruptions,greenhouse gas emissions,air-sea interactions,etc.It was highly believed that the decadal-scale temperature variations prior to industrialization period(1860s) were largely driven by solar irradiance and volcanism,while the late 20th century warming was closely related to the rapid increase in greenhouse gases.Future study on the climate of past 2000 years will focus on revealing an accurate temperature process by improving the accuracy of climatic proxies,increasing the resolution of proxy-based temperatures,expanding the representative areas,and developing climate models.