High Arctic Warmest In 1,800 Years: ‘The Medieval Warm Period Was Not As Uniformly Warm As We Once Thought’



A “seminal” 2009 study in Science of Arctic temperatures found that human-caused warming had overtaken 2,000 years of natural cooling (see Figure). A new study of the high Arctic provides further evidence for that conclusion.

Story via Columbia University

Summers on the Norwegian archipelago of Svalbard are now warmer than at any other time in the last 1,800 years, including during medieval times when parts of the northern hemisphere were as hot as, or hotter, than today, according to a new study in the journal Geology.

The Medieval Warm Period was not as uniformly warm as we once thought–we can start calling it the Medieval Period again,” said the study’s lead author, William D’Andrea, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Our record indicates that recent summer temperatures on Svalbard are greater than even the warmest periods at that time.”

The naturally driven Medieval Warm Period, from about 950 to 1250, has been a favorite time for people who deny evidence that humans are heating the planet with industrial greenhouse gases. But the climate reconstruction from Svalbard casts new doubt on that era’s reach, and undercuts skeptics who argue that current warming is also natural. Since 1987, summers on Svalbard have been 2 degrees to 2.5 degrees C (3.6 to 4.5 degrees F) hotter than they were there during warmest parts of the Medieval Warm Period, the study found.

Photo: William D'Andrea

Researchers produced the 1,800 year climate record by analyzing levels of unsaturated fats in algae buried in the sediments of Kongressvatnet lake, in western Svalbard. In colder water, algae make more unsaturated fats, or alkenones; in warmer water, they produce more saturated fats. Like pages in a book, the unsaturation level of fats can provide a record of past climate.  So far, most Arctic climate records have come from ice cores that preserve only annual layers of cold-season snowfall, and thus cold-season temperatures. But lake sediments, with their record of summertime temperatures, can tell scientists how climate varied the rest of the year and in places where ice sheets are absent.

“We need both ice core and lake sediment records,” said Elisabeth Isaksson, a glaciologist at the Norwegian Polar Institute who was not involved in the study. “Here, Billy has found something that tells a different, more detailed story.”

In looking at how summers on Svalbard varied, researchers also discovered that the region was not particularly cold during another recent anomalous period–the “Little Ice Age” of the 18th and 19th centuries, when glaciers on Svalbard surged to their greatest extent in the last 10,000 years and glaciers in many parts of Western Europe also grew. They suggest that more snow, rather than colder temperatures, may have fed the growth of Svalbard glaciers.

Evidence from tree rings and ice cores shows that southern Greenland and parts of North America were warmer from 950 to 1250 than today, with the Vikings taking advantage of ice-free waters to settle Greenland. Some regions also saw prolonged drought, including California, Nevada and the Mississippi Valley, leading some scientists to coin the term Medieval Climate Anomaly to emphasize the extreme shift in precipitation rather than temperature. A natural increase in solar radiation during this time was responsible for warming parts of the northern hemisphere, with a rise in volcanic activity from 1100 to 1260 causing milder winters, University of Massachusetts scientist Ray Bradley explained in a 2003 Perspective piece in Science. Bradley is a co-author of the Svalbard lake sediment study.

Western Svalbard began to gradually warm in 1600, the researchers found, when the northern arm of the Gulf Stream, known as the West Spitsbergen Current, may have brought more tropical water to the region. In 1890, the warming began to accelerate, with researchers attributing most of the warming since about 1960 to rising industrial greenhouse gas levels. Ice cores from Svalbard, by contrast, show a slight cooling over the last 1,800 years. The conflicting evidence suggests that temperatures may have fluctuated more sharply between winter and summer, said Anne Hormes, a quaternary geologist at the University Centre in Svalbard who was not involved in the study.

D’Andrea and his colleagues dated their lake cores by analyzing grains of glass spewed by volcanoes hundreds of miles away in Iceland. Those past eruptions– Snæfellsjökullin 170, Hekla in 1104 and Öræfajökull in 1362—all left unique chemical time markers on Svalbard’s lake sediments. “We know fairly precisely when these eruptions occurred, which is rare in the geologic record,” said study co-author Nicholas Balascio, a scientist at University of Massachusetts, Amherst.

Recent temperature measurements show that the Arctic is warming twice as fast as the rest of the planet, with sea ice this summer shrinking to its smallest extent on record. Natural feedbacks are amplifying the warming as loss of reflective sea ice causes the ocean to absorb more of the sun’s energy, melting more sea ice, which causes more energy absorption, and so on. Climate models suggest that by 2100 Svalbard will warm more than any other landmass on earth, due to a combination of sea-ice loss and changes in atmospheric and oceanic circulation, according to the International Panel on Climate Change 2007 report. In a study published last year in the journal Advances in Meteorology, Norwegian researchers estimate that average winter temperature in Svalbard could rise by as much as 10 degrees C, or 18 degrees Fahrenheit.

The study was funded by the U.S. National Science Foundation and the Keck Geology Consortium. The study’s other authors are David Vaillencourt, Nicholas Balascio  and Ray Bradley of the University of Massachusetts, Amherst; Al Werner, Mount Holyoke College; Steven Roof, Hampshire College and Michael Retelle, Bates.

This piece was originally published at Columbia University’s Earth Institute.

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14 Responses to High Arctic Warmest In 1,800 Years: ‘The Medieval Warm Period Was Not As Uniformly Warm As We Once Thought’

  1. Dr. Strangegas says:

    How can a study “undercut skeptics” who had nothing to stand on in the first place?

  2. fj says:

    Terribly interesting work and damning to those climate moles.

  3. Cugel says:

    I can almost hear McIntyre now, lecturing the authors on how tephrochronology should be done (which, it goes without saying, will not be the way[i] they[/i] did it).

  4. David Rice says:

    “…and undercuts skeptics who argue that current warming is also natural.”

    Skeptics do not make that claim: denialists do.

  5. Jack Burton says:

    The main denier’s case is that natural cycles are proof that human fossil fuel burning could not affect climate. If climate is always reacting to natural forces, as we know it is, it can just as well react to human induced rises in CO2 emissions. Somehow this simple fact is something deniers LOVE to deny. Of course it is willful ignorance, deep down they know better, but they can’t stand their political dogma being offended by climate science.

  6. David B. Benson says:

    Beautiful place.

  7. ColoradoBob says:

    Meanwhile in the real world …..

    Rotting whale meat lures record 80 polar bears to Kaktovik whale meat lures record 80 polar bears to Kaktovik

    More proof that another creature has lost it’s home. Polar Bears are like the homeless on our streets. Think of that bowhead whale as Polar Bear soup kitchen.

  8. ColoradoBob says:

    Meanwhile in the real world …..

    As they have for the past few years in what’s become a fall tradition in Northwest Alaska, walrus have begun moving toward shore near the community of Point Lay. Though no more than a small number have arrived so far, if this haul-out resembles others since 2009, there could soon be thousands of walrus populating the Chukchi Sea shoreline.

    The U.S. Geological Survey has dispatched biologists to Point Lay to begin observing the animals, which are coming in a little later than usual thanks to a few fortunate ice floes that they were able to inhabit until earlier this month. One such floe, measuring 30-by-12 miles, delayed Royal Dutch Shell’s Arctic offshore oil drilling operations as it floated by.

  9. ColoradoBob says:

    Meanwhile in the real world …

    “The number of dead trees on 750 million acres of public and private forests across the U.S. is on the decline for the second straight year largely due to the fact that the forests’ scourge, the mountain pine beetle, is running out of its favorite food ……….. ”

    Author: Pine beetles thick as rain clouds over British Columbia

    “And that’s attracted swarms of mountain pine bark beetles so large, they get mistaken for rain clouds on airport radars in Prince George, B.C. The combined weight of beetles in the infestation over Homer, Alaska, equaled 3,300 killer whales, or half a million wolves flying over the forest.”

  10. The ‘”skeptics” are running out of what Ayn Rand called “intellectual ammunition.”

  11. Spike says:

    They will just adjust the dates they use and claim the Arctic was warmer 3 000 years ago or some other date plucked from Google. They don’t need the luxury of firm evidence.

  12. syd bridges says:

    It’s funny how “that thar Hockey Stick” keeps turning up, like the grin of the Cheshire cat. It could soon haunt “Mitty in Wonderland” in the same way. No doubt M&M will do a million simulations and cherry pick the three that give a Hockey Stick too.

    However, after what we have witnessed in the Arctic this summer and the related drought in the US, I don’t think the fantasists and outright liars of the of the climate science denialists will have much credibility left. The laws of physics bow neither to religious bigots nor to free market economists. I know they should, of course, but as someone once remarked, “Facts have a Liberal bias.”

    This paper simply reinforces what anyone with knowledge of the ongoing disaster in the Arctic already knew-that we have pushed global warming to the point where we are now seeing the serious consequences. As Neven Acropolis says, we are now in the Age of Consequences. The party was great while it lasted, but now there is the small matter of the hangover, which is lkely to punish far beyind the third and fourth generation.

  13. I just had to laugh at your sharp and witty response. A good chuckle.

    But my friend, what of the fine bowl of cherries they’ve picked for themselves? Medieval Warm Period, Antarctic Sea Ice, The Latest Warming Plateau? Oh, it gets stranger, the endless mythology of ‘the global warming that isn’t,’ cameras and news sources like Fox focusing in on every snowflake for the chance to scream ‘see global warming isn’t happening,’ and then the wonderful set of fools who like to stick their fingers in their ears and chant the equivalent to ‘shananananana’ every time they hear a set of facts that risks removing their head from the sand.

    No legs to stand on? Absolutely. More like an ostrich’s bulbous body supported by a neck protruding from where the attacked head was buried in the sand so long ago. The legs, long since atrophied, have fallen off.

  14. Not much space to move before they run up against a period before the last ice age. I can see to denialists now. ‘See, there was a period of no Arctic sea ice at the end of summer 2 million years ago! See, the Arctic was ice free year-round ten million years ago! See, the world was twelve degrees hotter 50 million years ago!’

    It’s hard to imagine a more bizarre and backward set of reasoning.