Climate in northern Europe reconstructed for the past 2,000 years: Cooling trend calculated precisely for the first time
Date: July 9, 2012
Scientists have published a reconstruction of the climate in northern Europe over the last 2,000 years based on the information provided by tree-rings. Researchers used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC. In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
Yes, from 2012, so a couple of years back. But somehow I’d missed it. Uses tree rings, but does it in a smart way with well preserved trees from under sediments / fossils.
What did they find?
A long term down trend. Fairly warm MWP and Roman WP, with cold half cycles following each. Present warming not at all unusual.
An international team that includes scientists from Johannes Gutenberg University Mainz (JGU) has published a reconstruction of the climate in northern Europe over the last 2,000 years based on the information provided by tree-rings. Professor Dr. Jan Esper’s group at the Institute of Geography at JGU used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC. In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
“We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low,” says Esper. “Such findings are also significant with regard to climate policy, as they will influence the way today’s climate changes are seen in context of historical warm periods.” The new study has been published in the journal Nature Climate Change.
Well Golly! It actually got published, and without a hokey hockey stick…
Then they actually give a (polite) small slap to the IPCC:
In addition to the cold and warm phases, the new climate curve also exhibits a phenomenon that was not expected in this form. For the first time, researchers have now been able to use the data derived from tree-rings to precisely calculate a much longer-term cooling trend that has been playing out over the past 2,000 years. Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium due to gradual changes to the position of the sun and an increase in the distance between the Earth and the sun.
“This figure we calculated may not seem particularly significant,” says Esper, “however, it is also not negligible when compared to global warming, which up to now has been less than 1°C. Our results suggest that the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia.”
Looks to me like some small snippets of truth are finally being published, now that the attempted influence of editors has been exposed via the ClimateGate emails.
So the “net net” of it all is that we are continuing the very long slow slide into the next glacial (that takes a while to get rolling); and we have a roughly 1000 year ‘peak to peak’ warm excursion with peaks at about 0 A.D., about 1000 A.D. and about now. Guess what comes next…
Our present ‘warming’ on that graph is absolutely normal, and the next down turn will be to a lower low than the Little Ice Age. Though even the ‘fast onset’ wiggles like the one near 400 A.D. take a couple of hundred years to get from top to bottom, so “we” are unlikely to see the full drop in any one lifetime, and what things are like in 2400 A.D. will likely be a lot colder, but in a world far different from this one anyway. (Do you really think that 400 more years of Islamic Militancy, Nuclear Proliferation, and technological change will leave the world recognizable as being ‘just like now’? Think what the world of 1600 A.D. was like, and we are changing faster now, than then.)
We’ve also got a good 1/2 C of upside to maybe even 1.5 C of upside range (the Holocene Optimum was even warmer and is not on this graph) from present temperatures before we are ‘warmer than in the past’, and the past was pretty good, so in my book that means “No Worries”.
Overall, this trend says to me that IF we are very very lucky, burning all the carbon based fossil fuels we can might just slow our decent into the next Ice Age Glacial. Maybe. For a little while. If not, we get frozen, but that’s going to happen in any case, just a question of when. In no case can we keep making things warmer at a rate sufficient to permanently overcome the long term down trend AND the next cyclical dip of a couple of degrees C, and stay “like things are now”. At best, we drop to about -1.5 C instead of the deeper dip to -1.8 C otherwise expected compared to the Little Ice Age (i.e. to ‘about the same’ instead of ‘deeper due to downtrend’). But that would at least be not yet into the glacial. One hopes.
Then again, I’m pretty sure that CO2 does nothing in the troposphere and is a trivial addition to the radiative loss from the stratosphere, with water being by far dominant, so it’s most likely we just keep on ‘wobbling downward’ on that long term slope until we hit a water / ice knee and the Arctic stays frozen one summer. After that comes the much more rapid plunge into the Glacial. Hopefully not for another couple of hundred years. Maybe…