Introduction to the Holocene climate

In the ratified geological timescale of the International Union of Geological Sciences, the Holocene is a chronostratigraphical series and geochronological epoch that together with the preceding Pleistocene Series and Epoch constitutes the Quaternary System and Period. The stratigraphical reference point, or Global Stratotype Section and Point (GSSP), for the base of the Holocene is located in the NGRIP Greenland ice core at 1492.45-m depth and dated by annual layer counting to 11,700 ± 99 calendar year b2k (years before the year 2000 of the Common Era, CE). The Holocene is formally divided into three Stages and Ages: the Greenlandian, Northgrippian and the Meghalayan, equivalent to Upper, Middle and Lower Holocene subseries and Early, Middle and Late Holocene subepochs, respectively. The GSSP for the Greenlandian Stage Age is the same as for the Holocene. The GSSP for the Northgrippian is located in the NGRIP1 Greenland ice core at 1228.67-m depth and dated at 8236 ± 47 years b2k; it corresponds to the 8.2 ka (kiloannum) climatic event. The GSSP for the Meghalayan is defined in the KM-A speleothem from Mawmluh Cave in northeast India with a modelled age of 4200 ± 30 years BP (Before Present, relative to a baseline of 1950 CE), equivalent to 4250 years b2k; it relates to the 4.2 ka climatic event. The Holocene is unique within the geological record for the diversity and abundance of available evidence for past climate changes. Palaeoclimate reconstructions depend on the study of proxies—measured physical, chemical or biological properties that reflect important variables of the past climate, such as temperature, precipitation or moisture availability. Such reconstructions reveal the dynamics of Holocene climate changes on timescales ranging from orbital to subannual.