Last century, the Arctic had the lowest sea ice in the past 646 years

Anthony Watts has been keeping a relatively low profile lately.  Oh, he's put up plenty of weird articles such as those by greenhouse effect denier Tim Ball with his wacky conspiracy theories.  But Anthony himself hasn't been jumping in feet first too often in the last few days.  I've noticed more than once recently when he doesn't take much of a stand.  Instead he gives only a slight hint to his readers of the line he expects them to take.  (I guess he's getting weary of people pointing out just how silly he can be.)

Today's article about a temperature reconstruction in the Arctic is an example.  Anthony Watts posts a press release about this paper in PNAS by Jochen Halfar et al.  He provides one clue about how he wants his rabble to react by using the words "hockey stick" in his headline (archived here):

Inverse Underwater Hockey Sticks?

Apart from the headline, Anthony only provides one other little clue to tell his tamed denialati how to behave.  Anthony squeezes the word "claim" into a comment at the bottom of the copied press release (claim is a code word widely used by all and sundry, including HotWhopper, to mean "false claim" as in "that's what they claim, ahem".)  Anthony copies the following from PNAS, but prefaces it with his "They claim":

Significance
The most concerning example of ongoing climate change is the rapid Arctic sea-ice retreat. While just a few years ago ice-free Arctic summers were expected by the end of this century, current models predict this to happen by 2030. This shows that our understanding of rapid changes in the cryosphere is limited, which is largely due to a lack of long-term observations. Newly discovered long-lived algae growing on the Arctic seafloor and forming tree-ring–like growth bands in a hard, calcified crust have recorded centuries of sea-ice history. The algae show that, while fast short-term changes have occurred in the past, the 20th century exhibited the lowest sea-ice cover in the past 646 years.

From the above text, you are probably getting an inkling of what the researchers did and what they found.

The algae in question is called Clathromorphum compactum and can live for more than a thousand years.  The analysis can be compared to using tree rings to obtain information about past climatic conditions.  Here are some excerpts from the University of Toronto press release:

Almost 650 years of annual change in sea-ice cover can been seen in the calcite crust growth layers of seafloor algae, says a new study from the University of Toronto Mississauga (UTM).

“This is the first time coralline algae have been used to track changes in Arctic sea ice,” says Jochen Halfar, an associate professor in UTM’s Department of Chemical and Physical Sciences. “We found the algal record shows a dramatic decrease in ice cover over the last 150 years.”

With colleagues from the Smithsonian Institution, Germany and Newfoundland, Halfar collected and analyzed samples of the alga Clathromorphum compactum. This long-lived plant species forms thick rock-like calcite crusts on the seafloor in shallow waters 15 to 17 metres deep. It is widely distributed in the Arctic and sub-Arctic Oceans.

Divers retrieved the specimens from near-freezing seawater during several research cruises led by Walter Adey from the Smithsonian.

The algae’s growth rates depend on the temperature of the water and the light they receive. As snow-covered sea ice accumulates on the water over the algae, it turns the sea floor dark and cold, stopping the plants’ growth. When the sea ice melts in the warm months, the algae resume growing their calcified crusts.

This continuous cycle of dormancy and growth results in visible layers that can be used to determine the length of time the algae were able to grow each year during the ice-free season.

You can read more here at the University of Toronto.

From the WUWT comments

The article generated quite a few comments.  Below is a sample (archived here).

milodonharlani has an awful lot to say in the comments.  In his first contribution he decides that he likes this paper because it mentions the Little Ice Age.  But it doesn't mean what he thinks it means.  He says:

November 18, 2013 at 5:51 pm
Great to have some actual climate science practiced & published now & then.
As expected, the Little Ice Age had already begun by the 1360s, & Arctic ice cover has decreased during the past 150 years, as climate recovered from the LIA, which ended around 1860, after double bottoming during the sunspot Minima of Maunder c. 1645-1715 & Dalton c. 1790-1830.

Just the normal fluctuations of the Holocene, although with a disturbing longer-term (millennial scale) downtrend.

John, for some unknown reason thinks that Michael Mann doesn't accept the Little Ice Age when in fact he's contributed a lot to the world's understanding of it - for example see here and here.  And John would be very much mistaken if he thought this Arctic study in any way refuted the shape of the hockey stick.  He says:

November 18, 2013 at 5:58 pm
Once again, someone tell Michael Mann that the Little Ice Age really existed.
Too bad the mainstream media, when the pick up on a study like this, refuse to examine how it relates to the iconic hockey stick.

Janice Moore leaves her god out of it for a change and wails and shouts:

November 18, 2013 at 6:03 pm
A bona fide question from a non-scientist:

Re: “Longer periods of open and warm water result in a higher amount of algal magnesium.” (emphasis mine)

How do they know that the controlling variable is not the temperature of the water? How do they know that sea ice extent (i.e., amount of light) is a significant causation?

Isn’t a parallel (and erroneous) assumption commonly made about the controlling cause of tree ring width?

In other words….

How does this study prove ANYTHING?

(A kind soul later pointed out to Janice Moore some facts about photosynthesis.)


lowercasefred says "it's soot!":

November 18, 2013 at 6:45 pm
Q: How do they know the decreased ice cover is the result of climate warming instead of soot?
A: They don’t.

Manfred is happy enough with the research paper.  He's a greenhouse effect denier and would be happy with anything as long as "it's not CO2".  Manfred says:

November 18, 2013 at 7:55 pm
Another study matching well with either the sun or black carbon and not so well with CO2 as the main drivers in the Arctic.

Katherine is one who doesn't like unqualified "unprecedenteds", even when they are qualified in a time context and says:

November 18, 2013 at 7:58 pm
Their proxy covers less than 650 years and they have the gall to use “unprecedented”?! What idiots.

Appropriately named Mushroom George thinks the same algae must live in the southern oceans.  I doubt it, George.  In any case the seas around Antarctica tend to be free of ice in summer.  Mushroom George says:

November 18, 2013 at 8:07 pm
Recently, sea ice area increases in Antarctica seem to balance out most of the sea ice decreases in Uncle arctica. I would like to see algal growth rates from both poles compared.

Dr. Bob didn't bother reading the article but still says "scientists don't know nuffin'":

November 18, 2013 at 8:23 pm
Is there any data supporting the hypothesis that growth rings are directly proportional to temperature, sunlight penetration or maybe perhaps dissolved CO2. Unless you can prove that growth rings are proportional in width to some factor, it is hard to say anything about these data. It seems to me that people take for granted proportionality when they don’t have proof of concept.

I've run out of puff and can't be bothered reading any more comments.  You can read them archived here if you want to.  A few people are showing signs that their brain hasn't completely atrophied, but some those same people seem to think the scientists have no brains at all.

A little bonus for sticking through to the end

I'll leave you with a bonus.  There was a rather strange diversion in the comment thread, right into creationism.  Since it's been slow at WUWT lately, I'll copy it here.  Always good to read one ratbag science denier arguing with another ratbag science denier to see which is the bigger ratbag.  By the way - I think Stephen Meyer and David Berlinski must be creationists of one form or another :)

Janice Moore says (excerpt):

November 18, 2013 at 7:38 pm
Dear Milodon Harlani,
Have you ever watched the videos I linked? Every time I ask that, you do not answer. Did you think I did not notice? I think that, if you look into it, you will find that Dr. Stephen Meyer’s and Dr. David Berlinski’s credentials provide an excellent basis for their scholarship.

You accuse me of not learning, but you refuse to watch the lectures I posted (I only re-posted them because from your remarks, it was pretty clear that you had not watched them). How do you know that they are not well-reasoned and persuasive without listening to them?

milodonharlani says (excerpt):

November 18, 2013 at 7:54 pm
I don’t need to look into it, Janice Moore, because I’m thoroughly familiar with their total lack of credentials. They practically no knowledge of biology, except just enough to know that they are lying shamelessly, but don’t care, because they’re paid to hoodwink suckers like you. I’ve listened to their pack of lies for over a decade. To call their mendacity “scholarship” is the deepest possible insult to every scholar who has ever lived.

I don’t refuse to listen to your pathetic videos. I’ve heard them & talked to them in person. They’re paid liars, plain & simple.

I’m not the least bit in danger. It is you whose soul is in mortal danger. Your heroes are liars against the God of creation, Janine Moore. I pray you learn that before it’s too late.

God has revealed Himself to me through His creation. His Works in creating the universe(s) take precedence over your satanic, bibliolatrous, blasphemous interpretation of His Word. Wake up! You’ve been sold a bill of dangerous goods. Learn actual science instead of false religion. Worship the Creator & not a book written by men (& maybe one woman) trying to grasp the Infinite.

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J Halfar et al (2013); Arctic sea-ice decline archived by multicentury annual-resolution record from crustose coralline algal proxy; doi: 10.1073/pnas.1313775110