The climate of North America during the past 2000Â years reconstructed from pollen data

The temperature of the warmest month was reconstructed for the past 2000 years using 748 pollen sites from the North American Pollen Database. The Modern Analog Technique was used to quantify paleoclimate conditions using a modern pollen database with calibration sites from across North America. Across North America, both the Medieval Warm Period (MWP) and Little Ice Age (LIA) were cooler than the present (AD 1961-1990). The MWP was warmer than the LIA over at least the boreal and eastern portions of the continent and perhaps across the continent. These reconstructed anomalies during the MWP and LIA are significant anomalies from the long-term neoglacial cooling. The atmospheric circulation was likely dominated by a poleward shift of the summer Subtropical High Pressure system in the North Atlantic during the MWP.

► We use 748 pollen records from across North America to reconstruct the climatic conditions during the past 2,000 years. ► Temperatures during both the Medieval Warm Period Little Ice Age appear cooler than the past few decades. ► The climate during Medieval times was warmer than the LIA across North America. ► Results indicate a poleward shift in the position of Subtropical High Pressure Cells in summer during the MWP.