Reconstructions of annual summer precipitation and temperature in north-central China since 1470 AD based on drought/flood index and tree-ring records

The understanding of the ongoing climate change needs high-resolution records of the past, which are difficult to obtain in north-central China. Historical documents are unique materials for high-resolution (up to season) climate change reconstruction. Here, we report an attempt of quantitative climate reconstruction covering the main part of north-central China, by combining historical drought/flood index and tree-ring data. The rigorous verification tests confirm the fidelity of transfer functions used in the reconstructions. The precipitation and temperature anomalies/intervals were then defined based on the reconstructions. Finally, the intensity of several big droughts recorded in historical documents was re-examined and the dominant and recessive patterns of heat/water changes within the study area were identified. We concluded that (1) the droughts, occurred during the years of 1484 AD, 1585-1587 AD, 1689-1691 AD, 1784-1786 AD and 1876-1878 AD, were the results of rainless and torrid combination; (2) the droughts, occurred during the years of 1560-1561 AD, 1599-1601 AD, 1609 AD, 1615-1617 AD, 1638-1641 AD and 1899-1901 AD, were first caused by rainless summer, and then controlled by low precipitation and/or high temperature; (3) the droughts, occurred during the years of 1527-1529 AD, 1720-1722 AD, 1813-1814 AD, 1856-1857 AD and 1926-1930 AD, were first caused by torrid summer, and then controlled by both low precipitation and high temperature; (4) the dominant climate pattern within the study area consisted of warm-dry and cold-wet alternations, and the recessive pattern consisted of cold-dry and warm-wet alternations. We also showed that the drought/flood index is a valuable climate proxy in quantitative reconstructions, especially in places where tree-ring data is not available.