Climate variability in Northern Europe
A report from the World Bank is making rounds in media today. While portraying catastrophic scenarios, it contains no new actual research and is simply extrapolating statistical possibilities. Unfortunately the media headlines aren’t really reflecting the content – not unusual regardless of the topic.
However, it does give me an opportunity to post about some actual research that has taken place since the last IPCC report, while we wait for the new one to come out next year. The focus is on Scandinavia, both since I live here as well as it being one of the places where extensive climate proxies exist.
(Most Swedes know that in our recent history the climate has been both a lot colder as well as nice and balmy. We have no reason to believe our climate should stabilize)
“The level of warmth during the peak of the MWP (Medieval Warm Period) in the second half of the 10th century, equaling or slightly exceeding the mid-20th century warming, is in agreement with the results from other more recent large-scale multi-proxy temperature reconstructions.”
– B. Christiansen and F. C. Ljungqvist, The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability, Climate of the Past
“The record provides evidence for substantial warmth during Roman and Medieval times, larger in extent and longer in duration than 20th century warmth.”
– Esper et. al, Variability and extremes of northern Scandinavian summer temperatures over the past two millennia, Global and Planetary Change
And maybe one of the more interesting ones. This is an updated reconstruction by Briffa, famous for having authored one of the hockey sticks used by the IPCC. Apparently the stick has now disappeared.
Some previous work found that MXD and TRW chronologies from Torneträsk were inconsistent over the most recent 200 years, even though they both reflect predominantly summer temperature influences on tree growth. We show that this was partly a result of systematic bias in MXD data measurements and partly a result of inhomogeneous sample selection from living trees (modern sample bias). We use refinements of the simple Regional Curve Standardisation (RCS) method of chronology construction to identify and mitigate these biases. The new MXD and TRW chronologies now present a largely consistent picture of long-timescale changes in past summer temperature in this region over their full length, indicating similar levels of summer warmth in the medieval period (MWP, c. CE 900–1100) and the latter half of the 20th century.
– T. M. Melvin, H. Grudd and K. R. Briffa, Potential bias in ‘updating’ tree-ring chronologies using regional curve standardisation: Re-processing 1500 years of Torneträsk density and ring-width data, The Holocene
I’m quite Popperian when it comes to science. Feel free to voice hypotheses, but if they’re falsified they need to be scrapped and new ones looked into. There are many competing explanations as to how and why the climate on Earth changes and we’re not doing society a favor by only talking about one of them.
Especially when the actual science does not support the hyperbole.