The PAGES 2k consortium comprising 78 regional experts from 24 countries, produced a global array of regional climate reconstructions for the past 2000 years. They found although past global climate changes had strong regional expression, the most coherent feature in nearly all of the regional temperature reconstructions was long-term cooling trend, which ended late in the nineteenth century.

The research was initiated and coordinated by the ‘2k Network’ of the IGBP Past Global Changes (PAGES). The PAGES 2k dataset included 511 individual time series from natural archives that reflected temperature changes through various biological and physical processes. The proxies include tree rings, pollen, glacier ice, sediments from lake and ocean bottoms, historical documents, speleothems and corals. Through a comprehensive evaluation of huge data set, the researchers found that the 20th century ranked as the warmest or nearly the warmest century in all regions except Antarctica.

  During the last 30-year period in the reconstructions (1971-2000 CE), the average reconstructed temperature among all of the regions was likely higher than anytime in nearly 1400 years. Meanwhile, researchers pointed out that the study was not designed to assess the extent of which temperature change could be attributed to different natural and human-caused factors.
Dr. Ze-Xin Fan, head of the Tree ring and environmental change group from XTBG, participated in the work of Asian temperature reconstruction during the past millennia, and contributed tree ring data in the Hengduan Mountains of China.

The results entitled “Continental-scale temperature variability during the past two millennia” was published recently in Nature Geoscience, 2013 (6):339-346, doi:10.1038/ngeo1797.