Guest Post by Willis Eschenbach
Anthony has highlighted a study by Coughlin and Butler. Their study says that there is little or no urban warming (urban heat island, or UHI) in the temperature record from the Armagh Observatory in Ireland. They say:
It is concluded that temperature observations made at Armagh Observatory have been unaffected by rapid urbanisation over the past three decades.
Why is Armagh important? And is there really no UHI in Armagh?
The Armagh record is very valuable because it is one of the longest well-documented temperature series in existence. Here is the monthly mean temperature record from Armagh. (NOTE: I have replaced the earlier Figures 1 and 3, which only went up to the year 2004, with updated figures which now include 2005-2010. My thanks to those who wrote in with the location of the post-2004 data.)
Figure 1. 209 years of monthly temperatures at Armagh, Ireland. Pale blue is monthly surface air temperatures. Dark blue is Gaussian average of the temperature. Photo is noctilucent clouds over Northern Ireland.
My conclusions from Figure 1?
1. First, one single temperature station says nothing about the temperature of the planet. However, this one says a lot about century-long temperature changes in the North of Ireland.
2. The most striking thing to me is the slow regularity of the two-century-long temperature trend. Yes, there are decadal swings. But they don’t stray far from a simple trendline.
3. The recent warming from ~ 1980 on is not particularly unusual or anomalous compared to earlier periods of warming. From this, however, we can’t tell if there is a heat island signal in the record.
4. The Armagh data shows the same 0.6°C temperature trend over the 20th century that is shown by the global record. It also shows the same features as the global record, warming to the late 1940’s, cooling for thirty years or more, recent warming.
5. There is no sign of any acceleration, and indeed little change at all, in the long slow two centuries of warming.
Oddly, the Armagh Observatory data does not form part of the GHCN dataset that is used by all parties to create global temperature datasets. But I digress. Onward to the UHI.
First, some terminology. “UHI” stands for “Urban Heat Island”. Bad name. There’s lot’s of heat islands that are not urban. Trees, changes in the vegetation of the site, hedges, all of these can cause heat islands. I prefer the term “LHI”, for “Local Heat Island”. I know, I’m swimming uphill, so I call it UHI like everyone else does. But remember it doesn’t have to be urban.
The question of whether Armagh contains a heat island signal is an important one. Casting around for a way to determine the amount (if any) of heat island signal in the Armagh data, I decided to look at the relationship between Armagh temperature and the sea surface temperature (SST) of the North Atlantic and the Irish Sea. I reasoned that for an island on the edge of the North Atlantic, the SST would determine the land temperature. Here are the areas I used to see if my reasoning was correct:
Figure 2. Areas of ocean used for the comparison with the Armagh temperatures. Armagh Observatory is at the center of the yellow house. Left gridsquare is the North Atlantic area. Right gridsquare is the Irish Sea area.
I took the anomalies of the HadISST sea surface temperatures for each of those areas, and of the Armagh temperatures. Here are the results:
Figure 3. Temperature anomalies around Ireland. Monthly averages have been removed. Note that the vertical scale is different from Figure 1. Pale colored lines are actual monthly anomalies, heavy solid color lines are Gaussian averages. Sea surface temperatures (SSTs) are HadISST temperatures from KNMI.
Now, that’s pretty interesting. My observations, in no particular order, are:
1. As I suspected, the ocean temperature around the island of Ireland determines the Armagh temperature. The island is ruled by ocean winds and breezes.
2. The Irish Sea and the North Atlantic temperatures are quite similar. This increases confidence in the precision of the sea surface temperature data.
3. As you would expect, the swings in the land temperature extremes are greater than those of the sea surface temperature.
4. From 1900 to 1986, the averages of all three records are generally all quite close to each other. I always like seeing such a close correspondence of two entirely separate and discrete natural records. It increases the confidence in both datasets. In particular, the wiggle-match between the North Atlantic (heavy red line) and Armagh (heavy blue line) is quite impressive.
5. From 1986 onwards, the Armagh and the ocean datasets diverge in a significant manner.
6. The size of the divergence from 1986 to the end of the record in July 2010 is about a degree.
The Coughlin and Butler paper says:
The grounds surrounding the Observatory and its climate station have remained relatively unchanged over the past 200 years. However, in that time, the town of Armagh has spread in several directions, including to the north and east, past the Observatory site. Much of the development around the site has been in the form of housing built over the past 20-30 years and this development still continues.
Does this mean that Armagh is showing urban or site-specific warming over the last quarter century? I don’t know. But I find it mighty suspicious that after 85 years of running right in sync with both the North Atlantic Ocean and the Irish Sea, the Armagh temperature should suddenly strike out on its own towards new heights, just when the town starts building up around it.
As a result, I’m not prepared to agree with Coughlin and Butler that there is no UHI signal in the Armagh data. They say:
However, recent research into the historical temperature records and comparisons with present day data from rural weather stations indicate that any temperature differences which existed between the Observatory site and the countryside 20-30 years ago have not increased over the intervening years.
Comparison of Armagh with ocean data, however, clearly shows increasing temperature differences in the exact time frame which they have used in their paper to discriminate a valid signal.
My regards to all,
w.
PS – I can’t find any Armagh data after 2004 … does anyone know where it might be available? (Solved, thanks to those who wrote in.)
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Willis
I also meant to say that oil was spread on waves to reduce wave heights particularly during exercises etc. All in all a lot of oil was released, some burning some not.
I have no idea how that would affect the situation you describe
tonyb
Willis Eschenbach says:
August 29, 2010 at 8:27 pm
C&B claim that there is no UHI at Armagh, based on the fact that they find no spurious warming in the last 20—30 years w.r.t. rural records.
I find a clear signal of recent spurious warming in that exact timespan.
Does that mean C&B are wrong? By no means. It does raise serious questions about their results, however.
There are a number of ways that C&B could be wrong. Unfortunately, they compare Armagh to three “rural” stations which are not part of the GHCN dataset. Nor are they part of the ECA dataset. In fact, I can’t find any data on them. So I can’t find out if their results are valid, or not. We don’t know if their argument is “supported by the facts” as you put it.
Fair enough – but I did provide links to other UK/Irish station data which also show the same post-1980 warming trend.
polistra says: August 29, 2010 at 9:06 am
Here’s a quick-n-dirty fit of the Armagh ‘Storminess’ graph with a sunspot graph for
the same period:
http://ockhamsbungalow.com/blog23/armagh-storm-plus-sun.jpg
As you say, fit not good before 1850… but afterwards, excellent… this is surely worth exploring, maybe doing an article, because it looks as if it could be a significant fine-tuner to UHI correction. Plus, another support for the solar connection – and could it be an amplifying factor, something that helps amplify the apparently-too-weak changes in TSI????
???? Willis? anyone?
My wife went dress shopping, came home and exclaimed, “I found one and it was in the last place I looked”. (No kidding, you stopped looking after you found it.)
This is the flaw that most research has when it sets out to find evidence of global warming. If the observed first order effect supports AGW, the researchers declare they’ve found evidence of AGW and quit. It’s only when the first order effect fails to support AGW that they continue to pursue alternative explanations.
It is perhaps interesting to note how the slight warming trend appears to continue through the last decade, in a record that hasn’t been continually tinkered with.
Unlike the various global trends which have tended to show flattening over the last 10 to 15 years . Could that apparenting flatening in the global records, in fact be more of an artefact of earlier ‘tinkering’ to accentuate ‘current’ warming over the past ~10-15 years, in these global temps, which is now hiding a slow but nevertheless continuing warming, with an artificial cooling trend ?
For anyone who knew the past 5-15 years say, contained exagerations, it would be easier to dismiss of the apparent early 21 st century cooling, knowing that such tinkering had now hidden a steady warming trend ?
Could that be what’s meant when they say , there have been errors, but the overall trend/conclusions remain unaffected ? (ie Trust Us becuase we actually know better than the official record is now suggesting). ?
@ur momisugly Tenuc says August 29, 2010 at 2:38 am:
[/blockquote]We know UHI exists. We know the town of Armagh has spread in several directions, including to the north and east, past the Observatory site.[/blockquote]
Although I’d like to find reasons for a UHI in this case, I would dispute urbanized development north and east of the Observatory could have much of a bearing on the data, whether now or in the past.
@ur momisuglyPhillip Bratby says August 29, 2010 at 2:31 am:
[blockquote][Willis…]“I reasoned that for an island on the edge of the North Atlantic, the SST would determine the land temperature. ” Anyone who lives in these fair isles knows that to be the case. And the further west, the more the climate is dominated by the Atlantic. The further east, the more the continental effects become apparent.[blockquote]
I’ve had reason to look at European weather systems in the past, and the prevailing winds patterns are out of the northwest to southwest. If this is in fact the case, then development east and north would likely have little to no effect on the Observatory, since it is essentially “upwind” of the developments.
I think some other explanation is needed. I don’t think development down wind of the Observatory has any effect to speak of.
@ur momisugly David says August 29, 2010 at 2:42 am:
I could not agree with you more.
To look at GHCN data, lately I have been going to
All stations are listed with start and stop dates. Even stations that were only included for a few years are listed.
So if Armagh is one of the longest running stations in the entire world – and at a UK observatory, no less – it is not only surprising that it is not in the GHCN database, it is UNBELIEVABLE that it has evidently NEVER been included.
WTF????
@ur momisugly David says August 29, 2010 at 2:42 am:
I could not agree with you more.
To look at GHCN data, lately I have been going to
http://www.appinsys.com/GlobalWarming/climatedata.aspx?Dataset=GHCNTemp
All stations are listed with start and stop dates. Even stations that were only included for a few years are listed.
So if Armagh is one of the longest continuously running stations in the entire world – and at a UK observatory, no less – it is not only surprising that it is not in the GHCN database, it is UNBELIEVABLE that it has evidently NEVER been included.
WTF????
It’s the Fishin’! Around Armagh the fishin’ still OK. In the Western Pacific, Central Pacific, Eastern Pacific, Indian Ocean, South Atlantic, Northwest Atlantic, it’s terrible! If we didn’t fish so much, things would cool off fast. And all those supertankers, they’re at fault too ya’ know! The more life we have in the oceans and the less supertankers we have on the oceans means cooler oceans and, of course, that means more snow and ice for everyone. But, it is too late I fear. The oceans of the world have become cesspools and Mother Nature’s about ready to flush the toilet, again.
I have seen some records which indicated U.S. Army Second Infantry Division used Armagh area for a staging area. The US 654 tank Destroyer battalion and US Fifth Army also used this area. Having seen numerous military staging areas, it could be expected that much of the countryside was trampled, flattenned, turned from grass into mud/dirt parking aprons to support a huge influx of tanks, truck, etc. It would necessarily make sense that vegetation would take some time to be restored following end of hostilities and drawdown.
@ur momisugly Lucy Skywalker says August 30, 2010 at 1:59 am:
Very interesting graphs. Thanks, polistra!
A possible explanation for the pre-1850 mis-match:
With that being the Maunder Minimum/Little Ice Age, almost ANY gales would have had little sunspot activity to compare to. With 1798 being the start of the graph, and the curve declining right after that start, one wonders what the numbers would be before that.
That is actually informative, in that Atlantic storms were still active – and actually at a relatively HIGH level during the LIA. Among other things, this correlation of low sunspots with high gale activity would argue against the “warm climate = more storms” hypothesis. It would argue that there is no connection at all, given the data as shown. It argues that some other factors are important, not temperature as we currently evaluate it.
@ur momisugly Joe Spencer says August 30, 2010 at 7:03 am:
The global trend will never be reflected in EVERY locality. Some will be warmer and trend against the overall. The overall is an average, after all, meaning nearly half are above the curve and nearly half are below the curve. (A few ill match the curve.)
Willis Eschenbach says:
August 30, 2010 at 1:09 am
quote
My guess (and it is just a guess) for the reason for the World War II (WWII) decoupling of the air and sea temperatures is the huge amount of oil released from sinking ships. Hundreds of ships were sunk in the English Channel and the North Atlantic, each with thousands of gallons of fuel.
The interposition of this layer between ocean and air would tend to physically decouple the two. The effect of oil in preventing waves from breaking is legendary. Oil is deliberately released in sea rescues to calm the waves.
The breaking of wave-created bubbles and the lofting and evaporation of sea spray from breaking waves both transfers heat and creates cloud nuclei. Anything interfering with this process would slow the energy transfer between ocean and atmosphere, allowing the temperatures to decouple.
unquote
Well, anyone interested could google “the Kriegesmarine hypothesis” and see a fuller exposition. Here and at other blogs, and at my website, I have developed a totally original hypothesis of global warming. With the addition of silica run-off it even explains the collapse of the Grand Banks cod fishery and the supposed light isotope signature in the atmosphere.
quote
But that’s just my guess.
unquote
Up to a point, dear boy, up to a point.
JF
I think what you are observing as possible UHI is more likely an artifact of comparing measured point land surface air temperatures with modelled area SSTs. I compared the monthly average Armagh data (from 1948 to 2002) with the Reanalysis monthly averages of surface atmospheric temperatures at 55N 7W for the same time range. When the annual cycles are factored out, the slopes from 1985 are practically identical at 0.0611 and 0.0609 degrees per year. Since the Reanalysis values are calculated from multiple surface stations and satalite data for a mostly rural area, the UHI effect looks statistically insignificant.
Change “satalite” to satellite in my previous. I suggest you do further analysis before submitting for publication in a peer reviewed journal.
@ur momisugly John Finn says August 29, 2010 at 2:08 pm:
Malin Head station at the farthest north peninsula in Ireland from 1980 to 2006 seems to agree for the most part with your point here, indicating the ocean itself was going through the increase seen at Armagh. Interestingly Armagh and Valentia Observatory the last 2 years have dropped like a rock, while Malin Head has dropped significantly the last 3 years.
Quoting again:
@ur momisuglyPhillip Bratby says August 29, 2010 at 2:31 am:
Armagh seems to be tracking well with Venetia and Malin Head, both essentially ocean-dominated. That would seem to suggest the post-1980 rise is not UHI, but just a blip in the Armagh trend line.
Oops! In that last comment, the last paragraph should read
Armagh seems to be tracking well with Venetia and Malin Head, both essentially ocean-dominated. That would seem to suggest the post-1980 rise is not UHI, but just a blip in the Armagh-NEAtlantic*-Malin Head-Venetia trend line, which shows up in that Armagh trace above, as it does in the others. The closest Scottish station, Tirree also agrees. UHI is not needed to explain it.
@ur momisugly Fred H. Haynie at 11:02 am says the 55N/07W Atlantic grid (very close to Malin Head) tracks well, too. (However, 55N/07W is actually over land… I assume the grid is 5° and mostly water?)
All in all, it looks pretty consistent in that area: a rise above the long term trend in the region after 1980, which seems to be trending back down recently.
Fred H. Haynie says:
August 30, 2010 at 11:02 am
I, on the other hand, suggest you do some research on what exactly reanalysis “data” is before you start giving advice to others. It is not data in any sense of the word. Reanalysis “data” is a computer modeling of “homogenized” GHCN datasets. If you trust a computer model built on “adjusted” datasets, you don’t understand climate science at all.
“”” http://www.wrh.noaa.gov/climate/yeardisp.php?wfo=mtr&year=2010&span=Calendar%20Year&stn=KSJC “””
This link gets you a graph of the San jose Temperatures since the dawn of creation; including the two days of all time record high temperature for Monday and Tuesday of last week.
As is plainly clear from the graph; those two days of record high temperatures were not even worthy of a mention in the general scheme of all time record high temperatures; just a couple of ho-hum routine all time high temperatures for those dates; and as the graph indicates; the rest of 2010 has been generally lower than the normal.
So much for the weather is not climate file.
Willis,
Thanks for your suggestion. I ground truthed the Reanalysis model with three other Northern Ireland rural sites and came to the same conclusions. The model is apparently doing a pretty good job in that area or it is picking up UHI at those sites too.
Feet2theFire says:
August 30, 2010 at 1:28 pm
Oops! In that last comment, the last paragraph should read
Armagh seems to be tracking well with Venetia and Malin Head, both essentially ocean-dominated. That would seem to suggest the post-1980 rise is not UHI, but just a blip in the Armagh-NEAtlantic*-Malin Head-Venetia trend line, which shows up in that Armagh trace above, as it does in the others. The closest Scottish station, Tirree also agrees. UHI is not needed to explain it.
@ur momisugly Fred H. Haynie at 11:02 am says the 55N/07W Atlantic grid (very close to Malin Head) tracks well, too. (However, 55N/07W is actually over land… I assume the grid is 5° and mostly water?)
All in all, it looks pretty consistent in that area: a rise above the long term trend in the region after 1980, which seems to be trending back down recently.
Armagh is in pretty close agreement with all stations right across the UK and Ireland – including my home town (in the middle of England and the the CET record. The pattern is the same, i.e. strong warming from ~1980 and then a sharp drop in 2009/2010. I doubt there’s a significant UH influence.