Human-caused Arctic warming overtakes 2,000 years of natural cooling, “seminal” study finds

A Hockey Stick in Melting Ice


Arctic temperatures in the 1990s reached their warmest level of any decade in at least 2,000 years, new research indicates. The study, which incorporates geologic records and computer simulations, provides new evidence that the Arctic would be cooling if not for greenhouse gas emissions that are overpowering natural climate patterns.

So reports the National Center for Atmospheric Research (NCAR), which coauthored the study to be published in Science Friday [abstract here].  The Washington Post story notes:

The analysis, based on more than a dozen lake sediment cores as well as glacier ice and tree ring records from the Arctic, provides one of the broadest pictures to date of how industrial emissions have shifted the Arctic’s long-standing natural climate patterns. Coupled with a separate report on the region issued Wednesday by the World Wildlife Fund, the studies suggest human-induced changes could transform not only the Arctic but climate conditions across the globe.

It’s basically saying the greenhouse gas emissions are overwhelming the system,” said David Schneider, a visiting scientist at the National Center for Atmospheric Research and one of the Science article’s co-authors.

The same could be said about the entire planetary ecosystem — on our current path, we’re going to overwhelm the whole system (see “Intro to global warming impacts: Hell and High Water “).  Indeed, in some sense we already have, as a number of climate scientists have pointed out.  The NYT‘s Andy Revkin interviewed Thomas Crowley, a climate specialist at the University of Edinburgh:

“I would say that this is another piece of evidence that strengthens the argument that humans are now capable of preventing the onset of a future ice age,” he told me. Another scientist holding this view is James E. Hansen of NASA, whom I interviewed about the timing of the next ice age in 2003.

The NCAR graph appears to provide yet more support for the original, much-maligned “hockey stick,” which has been confirmed by recent analysis published in the Proceedings of the National Academy of Sciences (see “Sorry deniers, hockey stick gets longer, stronger: Earth hotter now than in past 2,000 years“):


The new study suggests (again) that the Medieval warm period was limited to only a part of the Northern Hemisphere, and that recent human-caused warming is quite outside the boundary of the last two millennia:

Darrell Kaufman of Northern Arizona University, the lead author and head of the synthesis project, says the results indicate that recent warming is more anomalous than previously documented.

“Scientists have known for a while that the current period of warming was preceded by a long-term cooling trend,” says Kaufman. “But our reconstruction quantifies the cooling with greater certainty than before.”

This new study made use of the “natural archives of Arctic climate”:

To reconstruct Arctic temperatures over the last 2,000 years, the study team incorporated three types of field-based data, each of which captured the response of a different component of the Arctic’s climate system to changes in temperature.

These data included temperature reconstructions published by the study team earlier this year. The reconstructions were based on evidence provided by sediments from Arctic lakes, which yielded two kinds of clues: changes in the abundance of silica remnants left behind by algae, which reflect the length of the growing season, and the thickness of annually deposited sediment layers, which increases during warmer summers as deposits from glacial meltwater increase.

The research also incorporated previously published data from glacial ice and tree rings that were calibrated against the instrumental temperature record.

The scientists compared the temperatures inferred from the field-based data with simulations run with the Community Climate System Model, a computer model of global climate based at NCAR. The model’s estimate of the reduction of seasonal sunlight in the Arctic and the resulting cooling was consistent with the analysis of the lake sediments and other natural archives. These results give scientists more confidence in computer projections of future Arctic temperatures.

Some of our leading climate scientists say this is especially important paper, as the WP piece notes:

Mark Serreze, director of the National Snow and Ice Data Center at the University of Colorado at Boulder, said the study was significant because it helps confirm scientists’ current understanding of how the earth’s climate has changed over millennia.

“It’s not that we don’t know how the climate works, it just we didn’t have anyone at that time measuring the climate forcing then,” referring to 2,000 years ago. “Climate doesn’t change all by itself for no good reason. Something has to force it.”


Robert Correll, who chairs the Arctic Climate Impact Assessment, said the paper in Science will likely “in the long haul become a seminal piece in the scientific literature” because it allows other climate researchers “to set their work in a long time scale.”

And Revkin’s print piece underscores the danger:

Jonathan T. Overpeck, a study author and climate specialist at the University of Arizona, said the rising concentration of long-lived greenhouse gases guaranteed warming at a pace that could stress ecosystems and cause rapid melting of Greenland’s great ice sheet.

“The fast rate of recent warming is the scary part,” Dr. Overpeck said. “It means that major impacts on Arctic ecosystems and global sea level might not be that far off unless we act fast to slow global warming.”

So now we know the answer to the question Robert Frost famously posed:

Some say the world will end in fire,
Some say in ice.

Fire it is — humanity’s burning of fossil fuels (and forests) trumps the natural ice age cycle.

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24 Responses to Human-caused Arctic warming overtakes 2,000 years of natural cooling, “seminal” study finds

  1. From Peru says:

    Richard Levangie: Are you kidding?

    Maybe the polar bears built invisible cities….or maybe there are secret Soviet cities there, built in the times of Joseph Stalin and still inhabited by the secret agents of Dr. No.

    It is the duty of James Bond to find the responsible for Arctic warming, Death to Dr No!

    Any other suggestions for the secret agents that Mr. Bond should unmask?

  2. Bob Wallace says:

    From, yes he is kidding.

    It’s snark. A tongue in cheek write up that plays off the absurdity of one of the denier arguments.

    I hope you read the linked article about a village of 229 individuals creating the heat island that has led to the incorrect temperature readings from the Arctic.

    Sort of theater of the absurd….

  3. GFW says:

    The linked article is great. Hmm though, From Peru has a novel idea the deniers can latch onto. *Secret* cities causing urban heat islands. I like it. No one really knows how many there could be :-)

  4. David B. Benson says:

    Why are there quotation marks around seminal?

    [JR: Because it was called “seminal” by an expert.]

  5. K. Nockels says:

    Thank-you Peru, Someone had to say it AGAIN! Some of the study’s they
    quote even say it if they ever bothered to read pass the first line. I saw the plane tour of Artic Sea Ice today too, and AGAIN it is not looking good. Now all we have to do is SOMETHING about it. Like reduce the amount of CO2 we are cramming into the air.

  6. Michael hauber says:

    The Mann 08 Hockey stick I’m quite sure is for Land and/or northern hemisphere only – the labelling on the chart is not clear. It is clearly not for the entire globe as the temperature rise from the late 19th century to now is much to steep, but is about right for land only or NH only.

    I find it quite odd that the anti hockey stick never seems to discuss this issue, or the fact that if you compare the Man 08 reconstruction to their preferred Loehle reconstruction the difference between MWP and little ice age is not that different (0.8 compared to 1.2), and seems to be about what you’d expect if 2 decent scientists independantly use different methods on different data to obtain a reconstruction in a field as obviously frought with uncertainties as this is.

  7. K. Nockels says:

    Wow Richard. What a stunningly sad sight and to know she will fall into the sea with the next calfing event. She stands for this short time as a tragic reminder of all we are losing of the natural world in our grab for the cash. Thank You for sharing that with us all.

  8. Rick says:

    So does this mean we were slowly sliding into an ice age for the past 2000 years before industrialization saved the day?

    I guess I’ll go read the post and find out.

  9. Zach H. says:

    I’m an avid reader of this blog and thanks for keeping me up to date on these pressing issues. I am wondering if anyone else noticed that Watts published the same report and reported it as more ammo for his contrarian views. I’m perplexed as to how he continues to cherry pick data and discount any data that is contrary to his own views of no AGW, yet his followers don’t notice… hmm. Thanks, Joe, for your continued vigilance.

  10. Bob Wallace says:

    A day-saver?

    Or more like the heroine’s flush of beauty just before her death from consumption?

    (Who wrote that classic piece of literature and what was it?}

  11. GFW says:

    Rick – if we’d stopped our industrial CO2 output around 1980 (or more precisely cut back output to an amount that kept the atmospheric concentration constant) then the answer would be yes. Temperatures around that level are definitely better for people than mini-ice-age temperatures. Trouble is, we didn’t stop, and we’re still not stopping. Therefore, temperatures are headed out of that happy medium and we’ll shortly get to see what too hot looks like, just as Europeans got to see what too cold looked like in the mini-ice-age.

  12. pete best says:

    Rick, No not an ice age but a cooling effect due to the earths angle of inclination and varying orbit around the sun. The big changes that cause ice ages resonate every 10-50,000 years called milankovitch cycles but many mini cycles happen in between these.

  13. Neil Hampshire says:

    The chart entitled “Hockey stick melting ice” shows a rapid rise in temperature around 1910.

    I Checked out the detailed HadCRU arctic temperature record shown on (Polar temperatures).

    The warming in the last 10 years was 1.5 degrees which is far less rapid than that experienced in the 1920’s (3.5 degrees).

    I have not yet heard anyone explain the dramatic 1920’s warming, which occurred way before any significant rise in CO2 levels.

    [JR: You should read the scientific literature. The 1920s was mostly a recovery from several major volcanoes. Robock discusses it.]

  14. Karl says:

    Robert Frost said it best:

    Some say the world will end in fire;
    Some say in ice.
    From what I’ve tasted of desire
    I hold with those who favor fire.
    But if it had to perish twice,
    I think I know enough of hate
    To know that for destruction ice
    Is also great
    And would suffice.

    If the choice is between a tropical planet, and another ice age, I’d favor tropical….

    [JR: That isn’t the choice. It’s between maintaining a livable climate, as close as possible to the stable climate of the last 10,000 years that allowed human civilization to thrive, and destroying the health and well-being of the next 50 generations.]

  15. GreenPRGuy says:

    Unfortunately, this news can also be reported as it was in today’s New York Times (page A16 in the print edition) under a headline that suggests climate change is saving us from an icy doom … a misinterpretation that skeptics will, at the very least, offer up with a hardy guffaw.

  16. Sable says:

    Karl, we are moving toward something beyond tropical – more like hellishly hot. The resources necessary for our survival will be vastly diminished. We will lose the wondrous diversity of plants and animals we have evolved with, and depend upon for our own existence. Ocean acidification alone will cause both mass extinction of marine life and the severe reduction of population in any survivors. The same applies to us.

  17. Bob Wallace says:

    Karl, this might give you an idea of what “hellishly hot” might look like and what we would experience on the way there.

  18. Mike#22 says:

    Zach H (#11) “I am wondering if anyone else noticed that Watts published the same report and reported it as more ammo for his contrarian views.”

    Not quite the same report–the graph Watts is showing is missing the last decade of warming that the NCAR graph does show. He points at a “step shift” at 1950, saying “All of the anomalous warming occurred in one “step shift” before 1950; while most of the increase in atmospheric CO2 has occurred since 1950…” and proceeds from there. His graph does not look like the one at the top of the post here, and his readers aren’t going to check whether Anthony has presented a complete picture.

    What is it about the hockey stick that gets the Wattsonians so worked up? I suspect that there are a lot of energy industry types, and also fossil fuel dependent industry types–air travel, petrochemicals, that sort of thing–who are really scared by the simple picture the hockey stick yields. People who see pipelines, tankers, furnaces, etc at their workplace. Good people who are completely unable to deal with the idea that their jobs are causing a planetary emergency. WattsUp must be a great relief for them.

  19. David B. Benson says:

    Here is an accurate summary:
    showing that, even without AGW, there will be no possiblity of an attmpt at a stade (massive ice sheets) for at least 20,000 more years.

  20. Dorothy says:

    Thank you, Joe. I wish everyone in my community would read your blog every day. Then they would better understand the real truth of the danger we’re in. Too many people I know, while considering themselves environmentalists, believe that if they become more energy efficient and agriculturally sustainable, things will get better, or at least stay the way they are. Of course this is not true. Though the effort towards sustainability is important, this won’t prevent unacceptable global warming by mid-century. We should be demanding our governments to invest in finding a way to remove huge amounts of carbon from our atmosphere as quickly as possible.

    Because the truth is so frightening, they are creating their own alternate reality – thinking comforting thoughts about working together and sharing their produce – and so are not impelled to make the big changes that will be necessary to save our world.

    Your readers have made very thoughtful comments to your post. If you all haven’t already done so, might I recommend you read Chris Hedges’ book, “Empire of Illusion.” I think you’ll find it pertinent.

    Fear is a powerful motivator if we allow ourselves to experience it. I’ve lived in a state of fear for seven years, since I first read about the projected loss of the Arctic sea ice. This isn’t the same as panic, which is not useful. And it doesn’t mean one can’t laugh and love. Or get pleasure from growing your own vegetables.

  21. paulm says:

    Well said Dorothy.

    I also recommend Gore’s The Assault on Reason.