Multi-archive summer temperature reconstruction for the European Alps, AD 1053–1996

We present a multi-archive, multi-proxy summer temperature reconstruction for the European Alps covering the period AD 1053–1996 using tree-ring and lake sediment data. The new reconstruction is based on nine different calibration approaches and errors were estimated conservatively. Summer temperatures of the last millennium are characterised by two warm (AD 1053–1171 and 1823–1996) and two cold phases (AD 1172–1379 and 1573–1822). Highest pre-industrial summer temperatures of the 12th century were 0.3 °C warmer than the 20th century mean but 0.35 °C colder than proxy derived temperatures at the end of the 20th century. The lowest temperatures at the end of the 16th century were ∼1 °C lower than the 20th century mean.

► Multi-archive summer temperature reconstruction for the European Alps. ► Highest JJA temperatures 1000–2000 AD occurred at the end of the 20th century. ► Sensitivity analysis suggests higher uncertainties prior to 1400. ► We therefore can’t conclude on how unprecedented current temperatures are. ► Sensitivity analysis highlights importance of data included.