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27 August 2012, 9.17am EST

Groundhog Day: The ice extent in the Arctic Ocean reaches a new minimum

A new historic minimum in Arctic sea ice provides additional evidence of rapid acceleration of Arctic ice loss, propelled, beyond a reasonable doubt, by anthropogenic greenhouse gas emissions.

Arctic ice around the Svalbard islands. Carlos M. Duarte, ATP project

Norwegian scientists just announced that the extent of Arctic sea ice has reached a new minimum, below that reached in the (boreal) summer of 2007 when an unprecedented catastrophic decline was reported. The 2007 minimum has been exceeded at a time when there is still a good 10 days of additional ice melting in the Arctic to go, and following reports of unprecedented widespread surface ice melting of the Greenland ice sheet.

Meanwhile Europe is leaving behind the northern heat wave this boreal summer, the US continues to struggle with crop failure due to unusually high warm temperatures and extended drought, and the Caribbean and Asian nations prepare for an intense cyclone season.

I received a phone call from a journalist this week interested in my thoughts on the new minimum of Arctic ice sheet, since I published a paper earlier this year, arguing that the dynamics of the Arctic ice sheet is signaling at the proximity of a tipping point.

In our conversation he asked whether I was prepared to speculate on the possible causes of this new minimum. I found the question a little perplexing and conveying an intense sense of deja-vú, as this is a recurrent experience every month of August for at least the past 6 years.

In the 1993 movie Groundhog Day), Bill Murray is a TV weather reporter who finds himself locked onto the same day, waking up to same sequence of events repeating themselves over an over on a loop.

I too have the sense that I am locked onto a time loop, where journalists declare themselves perplexed to report that the Arctic is actually melting, and convey this sentiment of surprise to the public, despite a wealth of research that:

identifies the Arctic as the region most rapidly warming on Earth (e.g. ACIA 2004)
predicts the steepest warming rates for the Arctic as a consequence of anthropogenic green-house emissions (e.g. Meehl et al. 2007)
predicts an acceleration of ice loss in the Arctic (e.g. Holland et al. 2006, Velicogna and Whar 2006).

If this was a one-off event, I could understand the surprise and questions around the causes of Arctic ice loss and its prospects for the coming years. However, there has been a series of recurrent minima starting in 1996 to date.. Given the close match between predicted and realised trends, perplexity at a new record melting event either signals that the robust scientific understanding available on the response of Arctic ice to climate change is met with skepticism or that this knowledge is still confined within the scientific community and does not percolate to media or the public.

Either option is unsatisfactory, because the developments in the Arctic are not locked in the realm of Arctic ice experts, but every citizen can follow daily the status of Arctic ice, and even check this on a smart phone through an app. The changes in the Arctic are broadcasted as if this would be a remake of the movie Death Watch, but this time involving the opportunity for a global audience to watch the demise of Arctic ice in real time.

Possibly, we scientists are to be blamed, as we cherish uncertainty so much that we deliver messages to the media crowded with caveats and cautionary alerts to possible uncertainties. The consequences is the messages passed on are confusing, with uncertainties overplayed relative to robust understanding, supported by both evidence and validation of predictions by observed trends.

For instance, earlier this month NASA scientists reported a surprisingly rapid spread of surface melting from affecting 40 to 97 % of the ice-covered surface of Greenland in only four days. However, the press release included the statement by Lora Koenig, a Goddard glaciologist and a member of the research team analysing the satellite data, that:

Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time. But if we continue to observe melting events like this in upcoming years, it will be worrisome.

This suggests that :

this event was not yet worrisome, and
that it was due to occur as expected from an apparent 150 year recurrence.

No connection was made in the note and associated statements to anthropogenic climate change, recent trends or predictions of climate models on the de-stabilisation of the Greenland ice sheet. So the notion conveyed was that this was a one-odd event that may be expected once every 150 years, unconnected to any previous trends or regional climate trends.

With so much evidence there, how can we continue to ponder on the possible ultimate causes of Arctic ice loss?

The noise on the climate change debate has reached such level that my colleagues in the US, particularly scientists within Federal agencies, tell me that they avoid taking a position on climate change in public conversations and news releases. The reluctance of the US public to agree with the wealth of scientific information pointing to an on-going and future warming of the climate due to anthropogenic green-house gas emissions seems to be curving now with the severe heat, drought and crop failure in the US this year. This curving NASA scientists now connect these heat waves to anthropogenic climate change (Hansen et al. 2012).

Nevertheless our predictions may turn to be wrong and our models can break in the future. Indeed, the statement “all swans are white” was almost a truism until black swans were discovered to the western world at the landing of Dutch navigators in the Swan River, WA.

We are certain to find “black swans”, now used as a synonym for the unexpected (Taleb, 2010), with ice trends in the Arctic, but, if anything these “black swans” are likely to consist on a yet faster acceleration of ice than expected, with the associated impacts on global climatic regulation.

The changes in the Arctic now meet the requirements to be considered “dangerous climate change” under the UN Climate Convention (Duarte et al. 2012a). The risk of ignoring these signals and taking serious action to mitigate climate change rests on the possibility that “dangerous climate change” will propagate, through existing tipping mechanisms in the Arctic, to the entire planet (Duarte et al. 2012a,b).

With all due consideration to uncertainty, policy makers need to accept the reality that ice loss in the Arctic is accelerating further, propelled, beyond a reasonable doubt, by anthropogenic greenhouse gas emission, and take due action.

Taking no action to mitigate climate change will eventually get us out of Groundhog Day to experience a new, unprecedented series of events.

But only to find a new reality of dangerous climate change spread, unchecked, throughout the planet.

Reference

ACIA. 2004. Impacts of a warming Arctic: Arctic climate impact and assessment, ed. S.J. Hassol.Cambridge:Cambridge University Press.

Duarte, C.M., T. M. Lenton, P. Wadhams and P. Wassmann. 2012. Abrupt climate change in the Arctic. Nature Climate Change 2: 60–62.

Duarte, C.M., S. Agustí, P. Wassmann, J. M. Arrieta, M. Alcaraz, A. Coello, N. Marbà, I. E. Hendriks, J. Holding, I. García-Zarandona, E. Kritzberg and D. Vaqué. 2012. Tipping elements in the Arctic marine ecosystem. AMBIO 41:44–55

Hansen, J., Sato, M. and Ruedy, R. 2012. Perception of climate change. Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1205276109 .

Holland, M.M., C.M. Bitz, and B. Tremblay. 2006. Future abrupt reductions in the summer Arctic sea ice. Geophysical Research Letters 33: L23503. doi:10.1029/2006GL028024.

Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper,I.G. Watterson, A.J. Weaver and Z.-C. Zhao, 2007. Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S.,D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Taleb, N.N. (2010). The black swan: the impact of the highly improbable (Second ed.). Penguin.

Velicogna, I., and J. Whar. 2006. Acceleration of Greenland ice mass loss in spring 2004. Nature 443: 329–331.

28 Comments

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28 Comments sorted by

Fred Pribac

logged in via email @internode.on.net

Thank you for this well stated article! I too was bemused by the implication that a 1 in 150 year event was something to be regarded as statistical business as usual and regarded as seperate from other extreme weather events including the well established recent arctic warming trends.

I also appreciate the handfull of critical references at the end of the article and would encoruage this practise with more authors on the conversation.

9 months ago report
1. Mike Hansen
  
  Mr
  
  In reply to Fred Pribac
  
  The 150 year average was based on the last 10,000 years and is deceptive. As Gavin Schmidt explains
  
  " the [1889] event was actually the only event in the last ~700 years, and there have only been 6 in the last 2000 years (4 of which were associated with the Medieval Climate Anomaly btw 750 and 1200AD). Hardly a frequently recurring ‘cycle’!"
  
  "The all-Holocene average that Koenig is referring to includes the warmer Early Holocene where orbital variability was driving warmer northern high latitude summers - and which is not relevant to the expected frequency in today's climate."
  
  http://dotearth.blogs.nytimes.com/2012/07/25/unprecedented-greenland-surface-melt-every-150-years/#more-45395
  
  9 months ago report
2. John Phillip
  
  John Phillip is a Friend of The Conversation.
  
  Grumpy Old Man
  
  In reply to Fred Pribac
  
  Fred, it IS 'statistical business as usual' if you look at time frames greater that a couple of thousand years.
  
  9 months ago report
3. John Nicol
  
  logged in via Facebook
  
  In reply to Mike Hansen
  
  I see. And what caused the Medieval Climate anomaly? Surely not carbon dioxide!
  
  9 months ago report
4. David Arthur
  
  n/a
  
  In reply to John Nicol
  
  I have read that the Mediaeval Climate Anomaly more or less coincided with a period of high solar activity (1090-1270 AD), and that Europe was further warmed by a coincident period of strengthening of the Gulf Stream (North Atlantic Oscillation?).
  
  In a draft paper working toward a reconstruction of Australasian temperature record over the last millenium is the following summary of Australian temperature trends in the period of the Mediaeval Climate Anomaly:
  
  "Between the Oort and Wolf minima…
  Read more
  
  I have read that the Mediaeval Climate Anomaly more or less coincided with a period of high solar activity (1090-1270 AD), and that Europe was further warmed by a coincident period of strengthening of the Gulf Stream (North Atlantic Oscillation?).
  
  In a draft paper working toward a reconstruction of Australasian temperature record over the last millenium is the following summary of Australian temperature trends in the period of the Mediaeval Climate Anomaly:
  
  "Between the Oort and Wolf minima, a period of high solar activity from A.D. 1090–1270, coincides with the ‘Medieval Climate Anomaly’ (MCA), a prolonged warm period identified in many regions of the Northern Hemisphere spanning A.D. 900–1250. [... According to a draft] Australasian temperature reconstruction, peak medieval warmth is observed around A.D. 1240–1360. This is somewhat later than described from Northern Hemisphere regions and overlaps with part of the Wolf solar minimum. The average temperature anomaly in the Australian region calculated over
  the warmest pre-industrial 30-year average A.D. 1238–1267 period is 0.09°C (±0.19°C) below the 1961–1990 climatology."
  
  I hope this helps.
  
  9 months ago report
5. John Nicol
  
  logged in via Facebook
  
  In reply to David Arthur
  
  Thanks for that explanation and detail David. It is very helpful.
  
  I also wonder if the more recent smaller, perhaps, increase in solar activity since the Maunder Minimum and consequent Little Ice Age together with the other subtle forms of planetary effects which are well establshed as causing the major ice ages, may not be responsible for the more recent abrupt warming from 1979 to 1995 which lead to the firmer establishment of the idea that increased CO2 was causing the warming because of…
  Read more
  
  Thanks for that explanation and detail David. It is very helpful.
  
  I also wonder if the more recent smaller, perhaps, increase in solar activity since the Maunder Minimum and consequent Little Ice Age together with the other subtle forms of planetary effects which are well establshed as causing the major ice ages, may not be responsible for the more recent abrupt warming from 1979 to 1995 which lead to the firmer establishment of the idea that increased CO2 was causing the warming because of the easily recognised correlation over that period between CO2 concentrations (from Keeling) and measured effective global temperatures. By "firmer establishment" I mean beyond the fairly speculative ideas of Arrhenius and Callendar.
  
  It does not always seem to be appreciated, as is the case for the earlier warm conditions on Greenland, and earlier Arctic melts, (whether of a 150 year cycle or not) when the sea ice North of Russia was much less than it is today (as in about 1922) and the North West Passage was open to shipping, that the rate of increase in global temperatures was actually faster in the 1800s than in the 1979-95 period and nearly as rapid from about 1925 to 1945 - I think.
  
  What puzzles me is that the surface and atmospheric temperatures do not appear from all of the measurements to have increased significantly since 1995, while apparently CO2 has increased even more rapidly than in the 1980s. Again there must be some unaccounted for influence on the climate which the modelling has not yet been able to include. This nrrds to be addressed in order for the models to be truly able to represent chages in the behaviour of the atmosphere.
  
  I do believe that the IPCC should by now be able to verify the effectiveness and accuracy of their models, to the degree that they can actually predict the climate in say 2014 and also hindcast the climate for say, 2000 through to 2012. This is something they have never promoted as being able to do as far as I am aware,and certainly in Chapter 8 - section 8.2.1 and 8.2.1.2 they state explicitly that they are only about to begin such hindcasting tests. To that time, they could only say that by adjusting parameters for each point in time, they could "make" the models reproduce roughly the climate for known years of climate, which of course demonstrated that the range of results obtained from the models could include "realistic" climate scenarios. However, this was then still a long way from saying that any model could confidently predict the climate for any given year, and of course even the temperatures found from the 23 selected models used for the 2007 report - AR4 - gave temperatures for doubling carbon dioxide which ranged from about 1 degree to 4.5 degrees, which again, is not a very convincing demonstration of accuracy, which of course they acknowledged.
  
  However, hopefully, we will see a more robust report come out next year where these problems should by then have been addressed.
  John Nicol jonicol18@bigpond.com
  
  9 months ago report
Timothy Curtin

Economic adviser

"Policy makers need to accept the reality that ice loss in the Arctic is accelerating further, propelled, beyond a reasonable doubt, by anthropogenic greenhouse gas emission, and take due action."

Appeals to "reality" need to be backed by statistical analysis. I see none in this article. What the authors need to do to substantiate their claim that ice loss in the Arctic is propelled by anthropogenic greenhouse gas emissions is first to explain why the intra-annual atmospheric concentration of CO2 is always lower in August-September when the ice extent is at its lowest, and always higher in January-March or April when the ice is deepest and widest.

As for emissions, they show little seasonal pattern worldwide, so why the wide intra-annual variations in Arctic ice extent?

9 months ago report
1. Jonti Horner
  
  Post Doctoral Research Fellow at University of New South Wales
  
  In reply to Timothy Curtin
  
  Before I dive in too deeply here, I'll preface this by saying I'm an astronomer, not a meteorologist or climate scientist. So don't take my word as gospel ;) However, I believe there's a lot of evidence to suggest that the unprecedented warming and loss of ice over the arctic is directly the result of anthropogenic climate change.
  
  I'm a regular reader of Dr. Jeff Masters' weather blog on Wunderground. Most of the time, his blog is about tropical weather, but in the past few years, he's talked…
  Read more
  
  Before I dive in too deeply here, I'll preface this by saying I'm an astronomer, not a meteorologist or climate scientist. So don't take my word as gospel ;) However, I believe there's a lot of evidence to suggest that the unprecedented warming and loss of ice over the arctic is directly the result of anthropogenic climate change.
  
  I'm a regular reader of Dr. Jeff Masters' weather blog on Wunderground. Most of the time, his blog is about tropical weather, but in the past few years, he's talked about the loss of arctic ice - particularly when unusual events have occurred. There's a wealth of info in the blog posts he's put up that covers why certain stochastic events have led to significant intra-annual variations in Arctic ice extent -- I'll put a few links at the end of my reply, for your perusal.
  
  So, as I understand it, a number of things can come together to make a given arctic melt season more (or less) dramatic than the last. The location of the jet stream, and in particular the phase of what is known as the North Atlantic Oscillation seem to play a major role.
  
  As for why arctic ice extent is at its lowest in August-September, when the intra-annual atmospheric CO2 content is lower than in Jan-March (I don't know if that CO2 content comment is true btw, but I'll accept it :)) - well, that's fairly simply -- it's the end of the summer, and therefore, the end of the melt season.
  
  Comparing the CO2 between January and August is a bit disingenuous, in my opinion -- the ice is hardly likely to melt more in the middle of winter, after three months of darkness! Yes, there might be slightly less CO2 in the atmosphere in August than January - but at the same time, there is definitely more CO2 in the atmosphere in August 2012 than there was in, say, August 1992. And the difference between the two is far greater than that between January 2012 and August 2012.
  
  And having grown up in the northern hemisphere (I'm a brit), I'm personally not surprised to hear that there's less ice around in mid- to late-summer than in the middle of winter :)
  
  As I understand it, and again I stress that I'm not a specialist, the average extent of arctic sea ice has fallen by almost 7% per decade for the last few decades - a trend that can be seen here: http://icons.wxug.com/metgraphics/angela/nsidc_July_time_series_2011.png . That's pretty scary, from where I sit. In fact, it's not going to be too long until the arctic is essentially ice free at the end of summer.
  
  More remarkable are the openings of the north-east and north-west passages. For a few hundred years, people have been trying to sail those to cut huge distances off their journals from atlantic to pacific. If I remember right, neither pass was passable at all until recently. The first time in at least ~400 years that the northwest passage was ice-free and could be passed without an icebreaker was, I think, 2007 - and it's been open every summer since.
  
  Hope that all clarifies a few things :)
  
  Jeff Masters in April this year: http://swedish.wunderground.com/blog/JeffMasters/comment.html?entrynum=2065
  
  August 2011: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1875&page=14
  
  July 2011 - http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=1842
  
  September 2008: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1090
  
  August 2007: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=764&theprefset=BLOGCOMMENTS&theprefvalue=100
  
  October 2007, which discusses the Northwest passage: http://swedish.wunderground.com/blog/JeffMasters/comment.html?entrynum=826
  
  There are plenty more, but that's a starter :)
  
  9 months ago report
2. Jonti Horner
  
  Post Doctoral Research Fellow at University of New South Wales
  
  In reply to Jonti Horner
  
  Meant to also add re: the intra-annual variation in ice content - stochastic events like the very large, powerful, and unusual low pressure system that ploughed into the arctic a few weeks ago can have a major impact on the ice content in a given year - that system, if I remember right, caused a fairly significant drop in the ice coverage over just a couple of days, as the high winds and high seas helped to break up the ice. Such stochastic events will naturally lead to some variation from year to year - the important point isn't the wobbling about the trend, but the trend itself. And that is very, very clear cut.
  
  9 months ago report
3. Byron Smith
  
  PhD candidate in Christian Ethics at University of Edinburgh
  
  In reply to Timothy Curtin
  
  "why the intra-annual atmospheric concentration of CO2 is always lower in August-September when the ice extent is at its lowest, and always higher in January-March or April when the ice is deepest and widest"
  
  CO2 is always lowest during the NH summer because terrestrial vegetation is most productive photosynthetically during this period ("breathing in" the CO2) and highest in NH winter because terrestrial vegetation is most dorment during this period (and for deciduous species, leaf matter rots…
  Read more
  
  "why the intra-annual atmospheric concentration of CO2 is always lower in August-September when the ice extent is at its lowest, and always higher in January-March or April when the ice is deepest and widest"
  
  CO2 is always lowest during the NH summer because terrestrial vegetation is most productive photosynthetically during this period ("breathing in" the CO2) and highest in NH winter because terrestrial vegetation is most dorment during this period (and for deciduous species, leaf matter rots, releasing CO2). The NH has far greater landmass and biomass than the SH and so dominates the global annual CO2 flux. Watch the first section of the following video to see these seasonal changes in action, with the variation most pronounced in the NH where most of the vegetation is: https://www.youtube.com/watch?feature=player_embedded&v=bbgUE04Y-Xg.
  
  Simultaneously, solar radiation in the NH is at its highest during the summer months, meaning that Arctic sea ice melt is fastest during this period as the Arctic gets 24 hour sunlight. Conversely, during winter's perpetual darkness, ice forms on open water, expanding over the months of the "long dark".
  
  These two natural cycles have been ongoing for millennia.
  
  Anthropogenic climate change does not replace them, but simply bumps up the amount of solar radiation that is retained in the planetary system, making the natural annual summer Arctic melt more pronounced. Over a few decades, the relatively small imbalance in energy (it is only a small fraction of the total solar energy that is now being retained that was not before) builds in effect as the earth system as a whole contains more energy. Over 90% of this extra energy has gone into warming the world's oceans. A tiny fraction has gone into warming the atmosphere and another tiny fraction into melting ice (of which a further small fraction has gone into melting Arctic sea ice). The total amounts of energy are so large, however, that even a fraction of a fraction has been sufficient to reduce summer Arctic sea ice volume by something like 60-70% over the last three decades or so.
  
  Atmospheric CO2 concentrations is only one of many factor affecting temperatures, but over decade or century scales, shifts in CO2 concentrations can have major impacts on temperatures - and consequently ecosystems.
  
  9 months ago report
4. David Arthur
  
  n/a
  
  In reply to Timothy Curtin
  
  Statistical analysis is not required for the purpose of Prof Duarte's "The Conversation" piece, particularly as Prof Duarte provides references.
  
  Coincidentally, the following articles have recently been published online at Nature Geoscience's website (http://www.nature.com/ngeo/journal/vaop/ncurrent/index.html), all pertinent to Arctic ice sheet dynamics.
  Progress Article: Törnqvist & Hijma, "Links between early Holocene ice-sheet decay, sea-level rise and abrupt climate change",
  Review: Carlon & Winsor, "Northern Hemisphere ice-sheet responses to past climate warming",
  Letter: Cronin et al, "Deep Arctic Ocean warming during the last glacial cycle".
  
  9 months ago report
5. Ian Musgrave
  
  Senior lecturer in Pharmacology at University of Adelaide
  
  In reply to Timothy Curtin
  
  A nice simple explainer about global warming (with references) to compliment the extensive references in this article is here
  http://www.skepticalscience.com/docs/Guide_to_Skepticism.pdf
  
  9 months ago report
Sean Lamb

Science Denier

Another view of groundhog day is presented by the fluctuation cycles of human penetration of Peary Land in Northern Greenland.
http://en.wikipedia.org/wiki/Peary_Land

Traces of human presence is found for periods of approx 600 years interspersed by longer periods when the ice crept back.
"Peary Land was historically inhabited by three Inuit cultures, during which times the climate was milder than presently:

Independence I culture (around 2000 B.C., oldest remains dating from 2400 B.C.)
Independence II culture (800 B.C. to 200 B.C.)
Thule culture (around 1300 AD)"

There seems to be no significant driving role of CO2 levels during these proxies for Arctic ice retreat. Sir John Franklin freezing to death in the North West Passage is not the Golden Age we should be harking back to.

Truly there is nothing new under sun, particularly the failure of science when politics or human careerism intersects

9 months ago report
1. Mike Hansen
  
  Mr
  
  In reply to Sean Lamb
  
  Arctic sea ice extent reconstruction for the last 1450 years.
  http://www.skepticalscience.com/pics/1-kinnard2011.jpg
  From
  http://www.nature.com/nature/journal/v479/n7374/full/nature10581.html
  
  9 months ago report
2. Sean Lamb
  
  Science Denier
  
  In reply to Mike Hansen
  
  Ahhh, a the reverse hockey stick maneoveur. I didn't see that one coming!
  
  I am sure the authors of that paper did the very best job they could, but the fact of the matter that short of a time machine, there is no way of verifying their reconstruction. In short it lacks what every viable scientific culture needs not to fall into complacency and academic politicing - contestability and falseability.
  
  I notice that the reconstruction doesn't seem to have detected any significant increase for…
  Read more
  
  Ahhh, a the reverse hockey stick maneoveur. I didn't see that one coming!
  
  I am sure the authors of that paper did the very best job they could, but the fact of the matter that short of a time machine, there is no way of verifying their reconstruction. In short it lacks what every viable scientific culture needs not to fall into complacency and academic politicing - contestability and falseability.
  
  I notice that the reconstruction doesn't seem to have detected any significant increase for the enormous volcanic eruption of 1260 which had thousands of Londoners buried in mass graves from starvation - suggesting maybe the proxies used are not as sensitive or as illuminating as the might hope. A common flaw in hocky sticks both positive and negative is they seem to contain some inbuild biases that are surppresing the variability of the past.
  
  Now if you look at the penetration of Thule culture around 1300
  http://en.wikipedia.org/wiki/Dorset_culture
  it is up around the very nothern tip of Greenland, after which it fell back south. And this is a cycle that seems to have happened going even further back
  Now look at this mid summer caculation of pack ice
  http://www.iup.uni-bremen.de:8084/amsr/ - still jammed packed around the top of Greenland.
  
  Can we really be sure that this area would be subject to traditiional human penetration under today's conditions? And if we can't be sure, isn't this as good and certain a proxy as we could ever hope for to demonstrate that recent Arctic ice retreat is nothing extraordinary - even in historical terms, let alone longer time frames.
  
  9 months ago report
3. Sean Lamb
  
  Science Denier
  
  In reply to Mike Hansen
  
  that Bremen link is a dud
  this is the proper link for looking at ice cover extent
  http://igloo.atmos.uiuc.edu/
  It just seems to be either done or not working on this computer.
  
  9 months ago report
4. Mike Hansen
  
  Mr
  
  In reply to Sean Lamb
  
  Sean. Given that you are a "mocker/climate science denier", I am quite certain that the science would have been a complete surprise to you.
  
  "proxies used are not as sensitive..." The error bars are shown on the reconstruction.
  http://www.skepticalscience.com/pics/1-kinnard2011.jpg
  
  Here is a revealing discussion at the Open Mind blog of the reaction of other fake skeptics to the new sea ice extent minimum.
  http://tamino.wordpress.com/2012/08/28/anthony-watts-breaks-the-record/
  
  9 months ago report
5. Sean Lamb
  
  Science Denier
  
  In reply to Mike Hansen
  
  I think you making a little joke here Mr Hansen - the error bars refer to the errors in measuring the proxies. If the proxy isn't a good reflection of the actual event, for example if it is flattening out past variation, the error bars won't tell us anything. In short, if the proxy is poxy then the error bars can't rescue it.
  
  But I am sure you didn't need me to tell you that.
  
  The fact is the archaeological record shows regular intervals of human existence in an area of Greenland that today is still ice bound. As they saying goes: the great tragedy of science, a beautiful hypothesis slain by an ugly fact. Alas when human careerism looms it head, Science tends to collapse.
  
  Here is another reconstruction of Greenland temperatures that seem to match the archaelogical record rather nicely - and show that we are still well within the range of normal variation.
  http://c3headlines.typepad.com/.a/6a010536b58035970c01310f4ff7a6970c-pi
  
  9 months ago report
6. Mike Hansen
  
  Mr
  
  In reply to Sean Lamb
  
  Sean's "hide the incline" graph has done the rounds.
  
  It was discussed by Skeptical Science here.
  http://www.skepticalscience.com/10000-years-warmer.htm
  
  "Easterbrook plots the temperature data from the GISP2 core, as archived here. Easterbrook defines “present” as the year 2000. However, the GISP2 “present” follows a common paleoclimate convention and is actually 1950. The first data point in the file is at 95 years BP. This would make 95 years BP 1855 — a full 155 years ago, long before any other global temperature record shows any modern warming."
  
  9 months ago report
7. Jonti Horner
  
  Post Doctoral Research Fellow at University of New South Wales
  
  In reply to Mike Hansen
  
  Thanks for that, Mike - I'd not come across that before, and it's pretty interesting :) I hadn't quite realised the lengths that some people are going to (whether by chance or design) to attempted to pervert the science to their own ends! Quite scary really..
  
  9 months ago report
8. Jonti Horner
  
  Post Doctoral Research Fellow at University of New South Wales
  
  In reply to Jonti Horner
  
  One thing that really troubles me about this whole "debate" is actually the way people are getting hung up on the whole "is it" and "isn't it" thing. While I'm personally convinced by the scientific evidence for anthropogenic climate change, I don't think you necessarily have to be convinced by that to see that changing our ways would be beneficial.
  
  As a gross oversimplification - lets assume that there are two ways that the climate could pan out - either we are causing global warming, or we aren…
  Read more
  
  One thing that really troubles me about this whole "debate" is actually the way people are getting hung up on the whole "is it" and "isn't it" thing. While I'm personally convinced by the scientific evidence for anthropogenic climate change, I don't think you necessarily have to be convinced by that to see that changing our ways would be beneficial.
  
  As a gross oversimplification - lets assume that there are two ways that the climate could pan out - either we are causing global warming, or we aren't. Lets call them scenarios A and B. In scenario A, mankind is irrevocably changing the planet's climate, whilst in scenario B, mankind is having absolutely no effect.
  
  Now, lets also assume that there are two possible responses - essentially, all or nothing. Lets call them scenarios Y and Z. In scenario Y, we do all we can to change our ways, while in scenario Z, it's business as usual. Lets have a look at the four combinations of these - I think it's interesting.
  
  Scenario AY - there is man-made climate change, and we do all we can to avert it.
  
  Here, we basically invest a large amount of money in finding alternatives to our current climate-damaging behaviours. We wean ourselves off fossil fuels, and develop new technologies, pumping a huge amount into R&D. In the short-turn, people pay a price - taxes go up, and there's inconvenience as the old ways change to the new - but in doing so, we avert disaster, and everyone lives happily ever after. Ok, so it won't be that simple, but you get my point. People benefit
  
  Scenario AZ - there is man-made climate change, and we do nothing to change our ways.
  
  This is essentially the worst case scenario. We carry on as we are, and the climate changes around us. Sea levels rise, drought and flood become more common - basically the ultimate nightmare scenario. Long term, the cost of doing nothing makes things far, far worse.
  
  ------------
  
  Both those cases are pretty simple - but what if man isn't causing the Earth's climate to change?
  
  Scenario BY - there isn't any climate change going on, but we act as though there is, and do all we can to change our ways.
  
  We spend a huge amount of money changing our ways - weaning ourselves off fossil fuels, and investing in new technology. In the short term, there might be a bit of a dip in standard of living - again, higher taxes, and the pain of moving off from our old ways. However, the invested money leads to new jobs, and the side effects of cutting out our production of greenhouse gasses most likely also causes a significant reduction in atmospheric pollutants. Fossil fuels are going to run out anyway - if we pump money into alternatives now, we can move away, and lead the world, and make a fortune selling the new technologies to them when the fuels run out. I'd personally still consider that such a scenario is win-win, personally!
  
  Scenario BZ - no man-made change, and we do nothing about it
  
  So here, it's business as usual. The climate doesn't change, and we're not all doomed. We do still have big problems with pollution, and the looming spectre of rising oil prices, and fuels running out or becoming unaccessible. At some point, we're going to have to address those problems ANYWAY, but because we stick with our current ways, someone else pumps the money into R+D. We keep consuming oil, and they make the killing on the new technology.
  
  --------------
  
  I appreciate that that's all a bit simplistic - but from where I stand, there are actually huge benefits to be gained by working as though man-made climate change is a real threat EVEN IF YOU THINK IT ISN'T. I don't understand people's resistance to the idea that we might be changing the climate - but I find it even harder to believe that people who have doubts are so resistant to trying to change things.
  
  There are huge benefits to be reaped by changing our ways regardless of what the climate is actually doing.
  
  Beyond that, though, it strikes me as a situation like buying insurance for your house. You make a relatively small investment now so that, if things go badly wrong in the future, you don't have to make a much larger and more painful investment at that point.
  
  At the end of the day - if climate change isn't real, and we were to invest in changing anyway, in the long term we'd still be better off - there'd be less pollution, we'd have new jobs and new technologies from the investment, and the precious resources we have that we're currently burning would be saved for other uses. If climate change is real, and we do nothing about it, then a whole world of bad stuff will happen.
  
  As I say, I'm convinced that man-made climate change is really happening, and is a major threat. However, I think that even if I wasn't convinced of that, I'd still think it was worth changing our ways, since we'll still reap the rewards of that change. Hope you can see what I mean :D
  
  9 months ago report
9. Sean Lamb
  
  Science Denier
  
  In reply to Jonti Horner
  
  "One thing that really troubles me about this whole "debate" is actually the way people are getting hung up on the whole "is it" and "isn't it" thing."
  
  Well, please excuse me for being interested in science - something of a rarity amongst climate change believers I expect.
  
  You can moan all you like about that graph, but if human occupation of Peary land is a good proxy - and I think it is - then it is likely to be giving a far more accurate picture than your Nature publication.
  
  There seems to be a cyclical pattern that allows periodic penetration of the Northern tip of Greenland - not a one off catastrophe driven by CO2
  
  9 months ago report
10. Byron Smith
  
  PhD candidate in Christian Ethics at University of Edinburgh
  
  In reply to Sean Lamb
  
  Sean claims to be interested in science and then treats a Wikipedia image created by a contributor without attribution of sources as gospel (moreover one whose implications for global climate can be interpreted as obvious), while rejecting a publication in Nature, probably the most prestigious scientific publication in the world.
  
  Oh, I've just noticed he linked earlier to second Wikipedia article, one with two sources: a 1925 journal article and a page in Danish consisting of an error message.
  
  9 months ago report
11. Sean Lamb
  
  Science Denier
  
  In reply to Byron Smith
  
  Golly, aren't I the scallywag. The nerve - claiming to be interested in science and then treating Nature dismissively.
  
  Lets just assume that Wikipedia has moderately accurate regarding summarising the archaeological record of Peary land - it is normally pretty good at things like that, although we can't rule out some rogue trolling Danes.
  
  If there is a record of cyclical human presence in Peary Land can we aggree that there is a possibility that the most presitigious scientific publication in the world has yet to get a firm grip on accurately reconstructing the historical record of pack ice in the Arctic?
  
  9 months ago report
12. Jonti Horner
  
  Post Doctoral Research Fellow at University of New South Wales
  
  In reply to Sean Lamb
  
  "Well, please excuse me for being interested in science - something of a rarity amongst climate change believers I expect."
  
  It's strange that you got that from my post, rather than considering the points I raised. I'm not surprised, though. As for an interest in science being the sole preserve of those who think climate change is a fraud - that's totally contrary to my own experience. In fact, in my day to day life, everyone I know who is deeply interested in science, including but not limited…
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  "Well, please excuse me for being interested in science - something of a rarity amongst climate change believers I expect."
  
  It's strange that you got that from my post, rather than considering the points I raised. I'm not surprised, though. As for an interest in science being the sole preserve of those who think climate change is a fraud - that's totally contrary to my own experience. In fact, in my day to day life, everyone I know who is deeply interested in science, including but not limited to those who work in a variety of scientific disciplines, are all wholly convinced by the vast weight of evidence that climate change is happening, and that we are the primary cause.
  
  The great majority of those I've met who instead believe that it's all a hoax typically have little or no scientific interest, beyond what they glean from their red-topped papers. I'm not saying all are - I'm sure there are many of those who are still to be convinced on the climate change debate who are fascinated by science. If there are, though, I'm gobsmacked that they're so resistant to the wealth of evidence that overwhelmingly points to the fact that our climate is changing, and that we are the main cause.
  
  If the history of occupation of Peary land is as you say, then that's fascinating - and I'm certainly interested in learning more about it :) Thanks for bringing it up :) However, I'm not convinced that just because there were periods in the past when these regions were marginally habitable that means that the widespread warming over the rest of the planet is invalidated - not is the unprecedented pace of that warming disproven.
  
  If there is a cyclical pattern that allows the local climate in Greenland to vary - that may well be something that would occur independent of climate change. However, that doesn't mean that the climate isn't changing - it might well be (and again, I'm an astronomer, so this is purely hypothetical) that variations in the precise location of the gulf stream resulting from the influx and freshwater from the Greenland ice cap would cause a periodic slight warming and cooling. Lets assume that, if Greenland warms, extra ice melts, releasing fresh water to the ocean. Over time, the salinity of the ocean near Greenland would fall. I could easily imagine a situation where that would act to slightly nudge the gulf stream further from Greenland. Now, as the Gulf Stream pulls away, Greenland would cool, as it is now surrounded by cooler waters, not fed from a warm source further south. At that point, the melting of the ice slows and stops, and the salinity of the ocean nearby slowly recovers as the fresher area slowly mixes out into the atlantic. This allows the gulf stream to return to its former location, albeit slowly, which causes the local climate to become warmer, increasing melting, and restarting the cycle.
  
  As I say, that's all my own speculation, and may have nothing to do with reality - but you can see that, in a situation like that, the climate of a small region would vary on decadal or even century-long scales, allowing periods of greater and periods of lesser habitability.
  
  Now, lets assume that while that cycle is going back and forth, something happens to cause the global climate to warm dramatically over a period of, say a century - a timescale shorter than the periodic variation going on in that locality. If that were to happen during a cold phase, then the local climate would warm as the global climate did so, causing the region to eventually become habitable again. At that point, the periodic cycle might be broken, particularly if the ice all melts!
  
  All purely hypothetical - but something that was fun to think up when I should have been eating my lunch ;)
  
  9 months ago report
Byron Smith

PhD candidate in Christian Ethics at University of Edinburgh

Thank you Prof Duarte for a timely and excellent summary of the ongoing rapid changes in the Arctic, setting record after record. This story ought to be at the top of the Con's main page.

It will not be too long before we have a seasonally ice-free Arctic for the first time in many thousands of years (quite likely tens of thousands of years or more). This has all kinds of implications. Neven, who runs what is probably the best known Arctic sea ice blog around has teamed up with Kevin McKinney…
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Thank you Prof Duarte for a timely and excellent summary of the ongoing rapid changes in the Arctic, setting record after record. This story ought to be at the top of the Con's main page.

It will not be too long before we have a seasonally ice-free Arctic for the first time in many thousands of years (quite likely tens of thousands of years or more). This has all kinds of implications. Neven, who runs what is probably the best known Arctic sea ice blog around has teamed up with Kevin McKinney to write a useful post summarising nine of them:
http://neven1.typepad.com/blog/2012/08/wasislac.html

1. Arctic ecosystem change/habitat loss.
2. Arctic (human) communities culture/infrastructure loss.
3. Albedo change to global energy budget.
4. Permafrost melt acceleration.
5. Methane clathrates destabilisation.
6. Greenland ice sheet melt acceleration.
7. Geo-political tensions over Arctic resources.
8. Exploitation of Arctic fossil hydrocarbon resources feedback.
9. Complex effects on NH wind/weather patterns via polar jetstream effects.

With a little pondering, I'd like to add another eight. I freely acknowledge that some of these are more speculative and I'd love to know of any credible research that covers them:

10. Disruption to the global energy budget from the freeing of the latent heat energy that previously was being used to accomplish the phase transition of ice -> water, though my back of the envelope calculations suggest that this is a much smaller issue than albedo change (I’d love to see some reputable work on this topic as I’m far from any kind of expert).

11. The release of persistent toxins and heavy metals that had become trapped in the ice.

12. The opening up of Arctic shipping routes which (a) reduces fuel needs of global shipping by cutting distances (negative feedback) but (b) brings more diesel fuel into the Arctic region, leaving black soot on glaciers (positive feedback). Not sure which is the larger effect.

13. Reconnection of marine ecosystems previously separated by ice with unpredictable ecosystem changes from invasive species. This is already occurring.

14. Opening up of Arctic fishing grounds to greater exploitation (and noise pollution).

15. Potential effects on thermohaline circulation. I haven’t seen any work on this related to seasonal sea ice loss, so I have no idea whether it is significant.

16. Potential effects on ocean acidification by increasing surface area for atmosphere-ocean gas exchange. Would this make any difference to ocean capacity to act as CO2 sink or rate of acidification? Maybe this is irrelevant.

17 . Highly visual and difficult to dispute sign of dangerous climate change, representing a potential tipping point in public awareness and concern. If we are waiting for that, however, before we make any serious efforts to slash emissions (esp if it doesn’t occur until 2030 or later), we’ll already have so much warming committed that we’ll pretty much be toast. At best, therefore, this point might consolidate public support for massive rapid emissions reductions already underway. But of course, by here, we've moved out of the geophysical and into the political systems, whose frequently non-linear behaviour is even harder to model.

(NB Editors: minor typo in the 5th paragraph of Prof Duarte's piece, which contains a superfluous parenthesis)

9 months ago report
Leo Kerr

Consultant

But isn't climate change 'absolute crap' or was it 'shit happens' - blood oath, I'm sure our opposition leader came to that conclusion through the immense computational power of his brain (he is after all a Rhodes scholar) so why should anyone believe the Arctic Ice melt has anything to do with carbon dioxide levels. I mean ice melts ffs.

9 months ago report
Jonti Horner

Post Doctoral Research Fellow at University of New South Wales

It isn't just the arctic ice that's melting away before our very eyes. Greenland has experienced a remarkable ice melt season this year - and I just found out that the mountains of Europe have experienced punishing heat, leading to some of them being snow free at their summits for the first time on record.

I lived in Switzerland for three years following the severe European heatwave in 2003. The thought that the Matterhorn could be snow free, even in mid summer, is chilling - not something I…
Read more

It isn't just the arctic ice that's melting away before our very eyes. Greenland has experienced a remarkable ice melt season this year - and I just found out that the mountains of Europe have experienced punishing heat, leading to some of them being snow free at their summits for the first time on record.

I lived in Switzerland for three years following the severe European heatwave in 2003. The thought that the Matterhorn could be snow free, even in mid summer, is chilling - not something I'd ever even imagined I'd see in my lifetime.

It's easy to doubt and argue over the voracity of anthropogenic climate change, and I'm continually amazed how many people are taken in by the idea that we could do nothing to change our climate - yet the evidence continues to mount. I wonder what it will take to change the minds of those who argue most vehemently that this is all a fabrication, and that all scientists are in cahoots to create a false terror with which to con extra grant funding out of the gullible public. It's just depressing :(

Here's the link to the really interesting blog article from Christopher C Burt, who does Wunderground's weather records blog (http://www.wunderground.com/blog/weatherhistorian/comment.html?entrynum=87#commenttop ), which brought this to my attention.

9 months ago report

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