The latest paper is one by Mathias Trachsel et al, titled: Multi-archive summer temperature reconstruction for the European Alps, AD 1053–1996. Moberg and Esper are among its authors.
They present a multi-archive, multi-proxy summer temperature reconstruction for the European Alps for the period AD 1053–1996 using tree-ring and lake sediment data. The results show that summer temperatures of the last millennium are characterized by two warm periods (AD 1053–1171 and 1823–1996) and two cold phases (AD 1172–1379 and 1573–1822).
But get this. The abstract states (my emphasis):
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.”
Now let’s assume the end of the 20th century proxy-derived temperatures are reliable. That would mean all the CO2 added by man over the last 1000 years (approx. 110 ppm) has led to a whole third of a degree Celsius of warming when compared to the Medieval Warm Period.
That’s it? This is a crisis?
Skepticalscience.com couldn’t find anything alarming either. All they could conclude was that the end of the 20th century in the Alps was a wee bit warmer than the Medieval Warm Period, that according to proxy data.
The added late 20th century tree-ring growth was probably due mostly to the CO2 enrichment.
That really should tell us and especially the IPCC something about the magnitude of feedbacks involving CO2 and water vapor.