Climate Feedback

Arctic amplification


Cross-posted from The Great Beyond

It’s Arctic ice time again. A paper in Nature on Arctic warming is getting some interesting and possibly somewhat misleading media pick-up. In their paper Rune Graversen and colleagues at Stockholm University use statistical analyses to try and understand what processes are important in the recent warming of the Arctic. One of their findings is that a substantial part of the warming is seen at altitude, rather that at the surface — “A remarkable result,” Graversen told National Geographic News. “I think nobody expected that.”

As that report and others (AFP, New Scientist) point out, the surprise is that this work diminishes the role of the “ice-albedo feedback” in recent Arctic warming. In theory less ice means more sunshine is absorbed, rather than reflected back into space, which means more warming, which means less ice, and so on and so on — a positive feedback that could be a powerful amplifier of climate change. But that effect would be felt most nearer the surface, not at altitude (The fact that some of the amplified warming takes place in the dark lends further weight to the argument).

Warming at altitude points to a role for increased energy transport by way of the atmosphere — warm and/or moist air moving north at greater rates than heretofore, and warming the Arctic both directly and indirectly (possibly through more water-vapour greenhousing and more clouds).

The AP’s take on this comes under the headline “Nature and Man Jointly Cook Arctic” (they’re referring to nature in its broad sense, not to our journal…) Seth Borenstein takes the line that the ice-albedo effect and anthopogenic warming are effectively synonymous, and that if warming isn’t due to the feedback but to increased atmospheric transfer of heat then it is more “natural” and less “man-made”. Unsurprisingly, a few blogs have taken up this notion.

But my reading of the paper doesn’t really support that claim. The researchers don’t say the increasing atmospheric heat transport is directly related to anthropogenic warming, but nor do they say it isn’t — and Graversen was explicit about this when talking to National Geographic News:

Nobody knows how much of this change is the result of human emissions of planet-warming gases such as carbon dioxide, but it’s likely that they play a role.

“Many models suggest an increase in energy transport when more greenhouse gases are introduced into them,” [Graversen] said.

“Changes in the circulation in the atmosphere might have had a much larger effect than previously thought, but these changes may also have been induced by greenhouse gases.”

So I’m a little surprised that the paper is being seen as evidence that the human role has been exagerrated. And I’m also a little surprised that, as far as I can see, no-one has picked up on the scariest part of it. The fact that ice-albedo feedbacks aren’t the whole story now doesn’t mean they don’t have a role to play, or that that role won’t increase in the future. In their conclusion, the authors make this point pretty explicit:

Our results do not imply that studies based on models forced by anticipated future CO2 levels are misleading when they point to the importance of the snow and ice feedbacks. It is likely that a further substantial reduction of the summer ice-cover would strengthen these feedbacks and they could become the dominant mechanism underlying a future Arctic temperature amplification.

Which is to say that, in the long run, the much discussed ice-albedo feedbacks could be the biggest factor of all — and we’ve already seen unparalleled amounts of warming before they’ve even kicked in…

Image: global view of Arctic Ocean from NASA Visible Earth / NASA JPL, University of Alaska – Fairbanks


  1. Report this comment

    Alastair B. McDonald said:

    This sort of dispute makes me sick with fear. It seem to be a case of the blind leading the blind.

    These days, science has become so specalised that no scientist dares to express an opinion on which he is not an expert, but when it comes to the engineering concept of feedback that seems to be fair game for every scientist who was once taught calculus.

    But in a dynamical system, cause and effect become blurred. For instance, if the Arctic polar vortex weakens, then the Arctic surface will warm and the sea ice will melt. If the Artic ice melts then the increase in water vapour will lead to a weakening of the polar vortex (and a warming in the atmosphere as the latent heat is released.) The question is that if the sea ice melts, is it because the vortex has weakened, or did the vortex weaken because the sea ice melted?

    The positive feedback effect of ice albedo, does not cause that happening, it only accelerates it. And the ultimate cause of the sea ice melting is forcing from the increase in concentration of carbon dioxide. Why it is happening so quickly is due to the positive feedback from the ice albedo.

    Of course the ice-albedo effect is not the cause of polar amplification. It is not a cause, only a feedback. The cause of polar amplification is that the greenhouse effect of water vapour depends on the sea surface temperture and so when the ice melts, the surface temperatures are driven exponentially higher!

  2. Report this comment

    Steven Earl Salmony, Ph.D., M.P.A. said:

    Dear Friends,

    Perhaps we can agree that global challenges, already visible on the far horizon, could soon be posed to humanity. Because economic globalization could be approaching a point in human history when it becomes patently unsustainable on a planet with the relatively small size and make-up of Earth, the current scale and unbridled growth of global consumption/production/propagation activities of the human species could produce a colossal wreckage of either the global economy or Earth’s ecology, even in these early years of Century XXI.

    If leaders are presented with a forced choice between protecting the global economy and preserving Earth’s ecology, it seems crystal clear to me that the leadership of the kind we have today will reflexively choose the economy…..first, last and always.

    What do you think?



    Steve Salmony

    AWAREness Campaign on The Human Population, established 2001

  3. Report this comment

    John L. McCormick said:

    I have not read the Graversen,, paper but noted it was initially submitted to Nature on March 27, 2007. It would be safe to assume the research and writing required several months. Likely it did not include any of the 2007 melt (post-submittal) and not much of the 2006 max melt either. So, an update on the research is in order.

    The Arctic sea ice melt records of the past decade confirm the fact that new ice in the western Arctic ocean predominates.

    New ice melts first and fast.

    It is a safe and certain assumption natural causes melt the sea ice.

    Dr. Chapman’s Cryosphere Today provides graphic evidence that Arctic sea ice melts each year – both from the east and west – along the ice margins. As that melt area increases in millions of square miles, the extent of new ice increases, in direct proportion, with the expansion of the melt area. In simplest terms, that creates lower albedo over a greater surface and more heat uptake in the ocean surface.

    As I review the daily images on Cryosphere Today, there have been events of massive sweeps of ice melt on the Eastern margin stretching almost to the North Pole. I am no scientist but I attribute that to ‘natural causes’ since there can be no other explanation, given the very short period of time – days -. Regardless, ice melt means new ice next summer, in that eastern region.

    New ice melts firstest and fastest.

    So, now that we have been offered new evidence that natural causes contribute to Arctic sea ice melt, how about giving some time and attention to studying what impact Arctic sea ice melt means to the world’s grain basket in Western North America.

    John L. McCormick

  4. Report this comment

    Steven Earl Salmony, Ph.D., M.P.A. said:

    Amused to death……..

    ……by Roger Waters.

    We watched the tragedy unfold

    We did as we were told

    We bought and sold

    It was the greatest show on earth

    But then it was over

    We oohed and aahed

    We drove our racing cars

    We ate our last few jars of caviar

    And somewhere out there in the stars

    A keen-eyed look-out

    Spied a flickering light

    Our last hurrah

    And when they found our shadows

    Groups ’round the TV sets

    They ran down every lead

    They repeated every test

    They checked out all the data in their lists

    And then the alien anthropologists

    Admitted they were still perplexed

    But on eliminating every other reason

    For our sad demise

    They logged the only explanation left

    This species has amused itself to death….

  5. Report this comment

    Dan Wentworth said:

    John McCormic,

    It would appear that you have been mislead by callous and or intentionally deceptive reporting in the popular media. There is nothing in this paper that indicates the effects measured are not caused by increases in atmospheric CO2 (the paper simply implies that at least some of the higher altitude warming is not caused by albedo changes). Indeed, some climate models predicted exactly this effect due to increased global convection caused by increasing CO2 levels.

    Please reread Oliver’s original post and check out the link to RealClimate that Olive provided (just above).

    The most blatantly deceptive report I have seen concerning this paper is this piece in the National Post.

  6. Report this comment

    Steven Earl Salmony said:

    How much longer can we afford to stand by and allow the absence of necessary constraints on the gigantic scale and growth rate of the global economy to produce the increasing probability of a colossal ecological wreckage in the future?

    If we keep doing what we are doing now, we will keep getting what are getting now, I suppose. Dire consequences could result from “staying the course” marked by the selfish, imperious choices of leadership to maximally expand the global economy, regardless of Earth’s limited capacity to support unlimited growth of big-business activity.

    By relentlessly growing the global economy and letting it run its current course, come what may, we could unintentionally end up threatening the lives of our children, biodiversity, global ecosystems and the integrity of Earth.

    What kind of a future do we intend for our children? If we keep doing what we are doing now, we could end up leaving our children a world that is unfit for human habitation. The integrity of the Earth and life as we know it could become dangerously undermined and irreversibly diminished by adamant efforts to endlessly expand the world’s interlocking national economies, to conspicuously argue for the unrestrained per capita consumption of scarce resources, and to continuously condone the unbridled increase of absolute global human population numbers on a relatively small, finite, noticeably frangible planet with the size and make-up of Earth.

    Perhaps our leaders will consider how the unrestrained industrialization activities of the human species could become unsustainable in this wondrous planetary home God has blessed us to inhabit ……….. and not to overwhelm, I suppose.



    Steve Salmony

    AWAREness Campaign on The Human Population, established 2001

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