In this video one of the authors of the paper explains what was done exactly (hat-tip to commenter Boa05att):
Edit: There's been some confusion due to my not being precise enough. The video below is from a previous paper, a couple of months ago, by the same group. The second paper extends the paleoclimatic data even further. Still the video below explains what was done exactly to retrieve the data and has fancy images of Lake El'gygytgyn. See the end of this blog post for links to more info.Blogger Alexander Ač sent me this short blog post to explain the implications:
Last time we had ~ 400 p.p.m. CO2 in the Arctic…
While the „denialosphere” is desperately trying to present their just-another-misunderstanding of climate science as a real scientific issue (search for “global warming stopped” meme), there is another *real* issue. To be specific: the last time planet Earth enjoyed a carbon concentration of around 400 ppm for a longer time period, average summer temperatures in the Arctic region were significantly higher.
According to the latest and most comprehensive paleoclimatic analysis, which brought us high resolution temporal data back to the Pliocene (Brigham-Grette et al., 2013, Science), summer temperatures in the NE Arctic region were ~8 °C higher compared to present-day climatology.
There are several recent paleoclimatic temperature reconstructions based on tree rings from the Arctic region. Two of them are presented in the following graph:
The graph shows temperature anomalies (relative to 1960-1990 climatology) during the summer in the Arctic region with a 10-year resolution in the last 2000 years (Kaufmann et al., 2009) (txt file). The second reconstruction shows newer analysis (Shi et al., 2012) (txt file), based on more proxy data and with a yearly time resolution. The shortest curve represents the instrumental temperature records according to NOAA (1880-2010) for summer temperatures in the Arctic.
The fit of the two paleo-reconstructions is not perfect, but the trends are similar, and warmer, as well as cooler periods in the past can be observed – the well known “Little Ice Age” and “Medieval Warm Period”. The recent “hockey stick” is also familiar to most people engaged in climate change discussion, since a similar trend is valid for the whole Northern hemisphere and the planet.
But there is more. What we already knew is that as CO2 concentration will continue to rise, global temperatures will do the same. Arctic region will warm even faster. Maybe some positive feedback loop will kick in. Maybe even more than one. But now things look even more complicated, since the recent work of Brigham-Grette et al. (2013) has shown us, what the area around the lake El’gygytgyn in the NE Arctic Russia (and by proxy also most of the Arctic) looked like last time, when CO2 concentration was approximately at the present level. Watch out:
Still concerned only about polar bears?
I'm not. Edit: But as Steve Bloom points out in a comment below (and graph maker Alex agrees), the graph gets the gist of what will happen in the Arctic under a business-as-usual scenario, but the graph's trend line might have another shape because of the +8 °C happening later than in 2100, and it's for Lake El'gygytgyn that is away from the Siberian coast. The Arctic could get much warmer still.
This is Arctic Sea Ice Blog post 500. Thank you for watching.
As a bonus to celebrate this joyous event I present to you this timelapse of a large calving event of Greenland's Helheim Glacier in July 2010 that has just recently been uploaded by the Swansea Glaciology Group: