One of the most common arguments that I see around the blogosphere (often on WUWT and Goddard’s Blog) is that the Arctic was in a similar climatic state during the early-to-mid 1900s. Previously we looked at predicting Arctic sea-ice extents over the last century and hypothesized that there was no period of similar sea-ice coverage as during the past 10 years. This result was previously confirmed by numerous sources but in particular Tamino had a great post on the subject. Today we will try and put the final “nail” in the coffin pertaining to previous periods of Arctic warming. Skepticalscience has already done a comprehensive work on the subject that may also be of interest.
I used a temperature compiling program to reconstruct all available temperature records between 66°N and 90°N. This data included 86 stations and covered the period 1880-2010 with the last two months missing for 2010 as would be expected.
Looking at the raw monthly data we can see pretty prominently that monthly temperature anomalies have been much higher since the mid-1990s than over any preceding period, with a large majority of high monthly values occurring post-2000s.
One of the best ways to look at data and eliminate potential sources of error associated with averaging over entire years is to use a 12-month running mean. An example of the averaging problem is where a strong El Nino may occur during the winter months and yet the temperature anomalies are broken into two years because the El Nino may have begun in December. Here is the result of the 12-month running mean.
Once again it is very clear that the last 20 years are anomalously warm in comparison to the remainder of the temperature record. In fact, prior to the mid-1990s there had never been a 12-month period with a temperature anomaly greater than 2°C but after this point there have been multiple occurrences. When we use yearly averages (January-December) we find a very similar trend. Of particular interest should be the 10-year running mean value currently being a full 1°C above the maximum during any preceding (pre-1990) period. Another interesting thing is that the centennial trend is 1.46 °C per century which is well above the Global trend and indicative of Arctic Amplification.
Now based upon this analysis, and previous analysis’ done elsewhere, I believe it is abundantly clear that the current Arctic warming is far greater than that which occurred during the early-to-mid 1900s. This supports the sea-ice results established here and puts another nail in the coffin for some outspoken skeptics.
Presumably you won’t practice the same degree of censorship here as I have just experienced at a certain other site of our mutual acquaintance?
[I won’t make any promises – Clearscience]
Fortunately the last great arctic warming was well documented.
[Yes and the previous arctic warm period is well demonstrated here and is shown in the predicted sea-ice records and the measured ones displayed at Tamino’s. I don’t think we need anecdotal evidence of a previous warm period in the Arctic, it is quite evident that there was one and perhaps many – Clearscience]
Reports from fishermen, seal hunters and explorers, he declared, all point to a radical change in climate conditions and hitherto unheard-of temperatures in the Arctic zone. Exploration expeditions report that scarcely any ice has been met with as far north as 81 degrees 29 minutes. Soundings to a depth of 3,100 meters showed the gulf stream still very warm.
[I would find it curious if one were to ask the “seal hunters” now about their views on ice changes… Nevertheless, I would not be shocked to find individual years with similar ice conditions in the past but not the frequency. What you should consider is that it is pretty well understood that there is a relationship between the Atlantic Multidecadal Oscillation and Arctic Sea Ice Extents/Temperatures. Note the previous period of warming coincides with a positive phase of the AMO, as well as the one during the late 1800s. The AMO in itself does not explain the current warming in the Arctic. See for yourself. Note the lack of agreement in the late 1800s is due to volcanism, Krakatoa, Navrupta etc… – Clearscience]
Great masses of ice have been replaced by moraines of earth and stones, the report continued, while at many points well known glaciers have entirely disappeared…
That introductory article also lists a number of other warming episodes.
The period was also the subject of a recent book (carried on my website) Here is the description and link with a foreword by me;
[If individuals want to read the content they can go to your website here – Clearscience]
Since NSIDC satellite records started in 1979, the late summer minimum extent in the Arctic has undoubtedly shrunk. It reached its lowest extent in September 2007 at close to 40% below the 1979-2000 mean baseline value and has recovered somewhat since then, but is still slightly more than 20% lower than the 1979-2000 baseline value.
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135
At the same time, Antarctic sea ice has grown: the late-summer minimum is around 18% above the 1979-2000 mean baseline value.
However the summer minimum extent in the Arctic has gone through previous periods of shrinking and expansion, most likely related to previous periods of warming and cooling, as well as shifts in wind patterns and ocean currents.
[Not for the last several thousand years, see Polyak et al. 2010 – Clearscience]
It seems that sea ice declined everywhere eventually during the period under review but some places later than others as these studies illustrate
Russian records show that it had shrunk to a low extent in the 1940s, when Arctic temperatures were also warmer.
ftp://ftp.whoi.edu/pub/users/mtimmermans/ArcticSymposiumTalks/Smolyanitsky.pdf
A separate study of Greenland temperatures shows that these were slightly higher in the 1930s than today, as well.
http://www.agu.org/pubs/crossref/2006/2006GL026510.shtml
[Until now – Clearscience]
The temperature record for Illulisaat, on the west coast of Greenland, near the mouth of the Jakobshavn Glacier, shows this same warming in the early 20th century, with temperatures in the 1930s and 1940s a bit higher than those of today.
[See the Arctic Report Card for an up to date summary across multiple Greenland stations rather than just one… – Clearscience]
Here are new links to the studies showing sea ice extent in Russian Arctic.
“Our results show that sea ice was most extensive at the start of the record and has since experienced two periods of decline, evident in the summer means. The first of these was during the 1930s–1950s (period A), and the second began in the mid-1980s and is still ongoing (period C).”
Note that the years following this warm period showed one of substantial temperature decline causing some scientists to believe we should prepare for a new ice age. Sea ice reached a maximum during the 1970’s which coincided with the advent of satellites. These records therefore show but a brief snapshot of our arctic conditions which illustrate the subsequent decline from a high ice period.
Tonyb
[I believe Tamino addresses this issue quite well – Clearscience]
[Not that I have any problem with you posting on the subject and I certainly don’t mind you making a clear concise argument that you feel sea-ice trends were as low during the early-to-mid 1900s and that the temperatures were similar, BUT I would prefer if you limited your responses so that they are clear and concise. Posting long essays with multiple links just makes it difficult for viewers to be able to quickly read and understand what you are saying so that is why I cut out so much. Once again, I have no problem with you challenging the content but if you could do so in an efficient manner it makes the discussion a lot more accessible. – Clearscience]
Yes you certainly have shortened it and removed some links. As for ‘anecdotal’ I think ciontemporary reports in newspapers and film are a pretty good riposte to temperature records, many of which come from stations 10 or 20 years after the melting finished.
tonyb
[I will have to put up a comments policy I suppose. I have no problem with discussion but long posts with many links (some would say in Joe Romm style) are not effective for creating discussion. And pertaining to the anecdotal comment, I believe qualitative versus quantitative is the question at hand. Personally, I don’t feel that articles in news papers from years ago are quite as scientifically robust as a statistical analysis such as that which has been presented, you can disagree, it’s your choice – Clearscience]
Its your blog and you can run it as you like. However if you set and dictate the agenda in a format that stifles open debate you will end up with another echo chamber where everyone has the same views and congratulates each other that they must be right because no one is disagreeing with them. You know the site to which I refer whose moderation policy seems to have been learned in North Korea. No doubt you will also acquire your sycophants who will continually murmur low level abuse. Is that what you want?
Anyway, good luck with your blog. Im sure I’ll see you pop up in other places where debate is allowed to be more open
best regards
tonyb
[I think I was more than fair to your previous comment. I responded accordingly and did not throw out accusations or anything of the sort. If you are frustrated that I snipped some of your text then that is your choice but I don’t want this blog to be inundated with paragraphs after paragraphs of text quoted from different newspapers and articles. You are obviously capable of formulating your response into a few sentences that illustrate the premise behind your thesis, why choose to not do so? I have no problem with open debate and I feel that in my response to your commentary that I was far more open than you gave me credit for. Because I presented evidence which countered your opinion does not make the debate closed. I thought I was very fair and even provided a 2nd link back to your blog where they could read further about the topics you brought up. I will not however allow for longwinded comments filled with links, quotations and missing a general direction to hijack the debate. If a person can’t read your comment and its links in a half hour then that’s a clue that this will not be helping to engage readership. It is your choice either way but backhanded comments such as “in other places where debate is allowed to be more open” don’t really help your case. – Clearscience]
So, if one isn’t allowed a full podium for a diatribe then you’re stifling discussion?
And putting anecdotal evidence on a par with robust temperature measurements?
Seriously?
Hopefully the Cryosat-2 data will put an end to the “It was hotter back in ______” memes.
Dunno if you saw this, but LHamilton posted these earlier today:
Basically, over the last 32 years, the trend in extent and ice edge latitude has shown a decline in ice cover in each month of the year (even in mid-winter months).
Sorry to go a little off-topic there.
BTW, nice post.
The Yooper
[Yeah I saw at least 1 of those graphs recently. I think it was a very interesting analysis approach. I think that Cryosat-2 data will help but be prepared that there may be surprises in either direction. You could see more than we expected or less than we expected. My guess is as good as anyone’s at this point although I tend to be in agreement with Dr. Barber on the subject. – Clearscience]
Clear science
Can I suggest that you formulate a ciomments opolicy where you set out your expectations from your readers and emphasise your own desire to promote an open and courteous debate open to all. There are too many examples of sites on both sides of the debate where overly partisan commentators shout down the other side and create a level of intimidation that means some readers are afraid to participate because of the bear pit atmosphere. That does the reputation of science no good, especially when some of the participants are key members of the science community.
Now that I know your liking for brevity, some of my own suggestions for a comments policy would be;
* No more than 500 words and or 2 links.
* No ad homs
* Removal of abuse
* Subsequent removal of off topic material after an intial polite warning
* Rules that are applied equally to both sides of the debate
* Attribution of comments by placing single or double ‘speech marks around them should be a direct and unchanged quotation from that person/article
Can I also respectfully suggest that when you edit a piece you are careful not to dilute its message?
You say in ‘about’ “We will see how my first foray into the explosively charged climate blogosphere goes.”
Running a blog is a thankless task as can be seen from the reaction from one of your first visitors and I am well known to be fair minded and reasonable. 🙂
With all good wishes for the succes of this new venture
tonyb
[I’ve tried to put together a rudimentary comment policy – Clearscience]
PS
I forgot to mention in reply to your earlier comment that I find you perfectly courteous .
Sorry for typos in the piece above-it was before my first coffee.
tonyb
[Thank you. I think that one of the most difficult things in beginning a blog is to get a grasp of how to deal with comments. It is as they say a “work in progress” – Clearscience]
clear science
I think you’ve done a nice job-the blog looks clean and modern.
I like the way that your replies are emboldened and follow immediately after the comment. That is helpful as on some blogs its almost invisiile and isn’t always noticed if the poster doesn’t go back and carefully re-read each thing already posted.
tonyb
Interesting info at <a href="http://clearclimatecode.org/analysis-of-canada-data/" ClearClimateCode on northern Canada data (64 – 90 north). Similar results, shocking rate of warming in recent years.
A point mentioned-
“The swings in this zone are much larger than the global average (this zone is 5% of the Earth’s surface); the recent warming in this zone is over 5 °C per century! “
[I’ve done work on modeling recent warming in parts of Northern Canada, manuscript in preparation. There is indeed an astounding rate of warmth, particularly since the mid-1990s in my study region – Clearscience]
When did your temperature records for Canada start?
tonyb
[My source region had a start date during the 1880s but the confidence before 1920 is seriously hampered due to station data availability. Some regions in Northern Canada are very isolated and many of the records before these points were more anecdotal and not rigorous in the same way as one would need for this kind of analysis. I’m a little hesitant to discuss many details at this point prior to acceptance or at least submission but when things get moving I will discuss some of the related issues – Clearscience ]
Your link comes up not found-can you please recheck
tonyb
[I’ve put the actual link in a new post on the subject. I thought it was interesting as my parents are Canadian. – Clearscience]
Hi CS
I don’t know if you ever saw the Jones/Briffa paper which attempted to reconstruct Greenland temperatures back to 1800? This also did lots of work on the early/Mid 19th century warming
I appreciate you are looking at the broader arctic
tonyb