Revisiting Temperature Reconstructions used in Climate Change Modeling

Guest post by Neil Catto

When considering historical temperature reconstruction there are three areas which need further examination; historical instrument readings and adjustments for UHI, tree-ring proxies, other paleoclimate proxies and ice-core proxies. To predict the future of climate it is necessary to have a very good reconstruction of past information.

Instrument Record:

Most, if not all, climate models use the Central England Temperature (CET) record to compare historical temperatures with model outcomes [hindcasting]. The CET is the longest instrument record of temperatures in the world, dating back to 1659.

CET temperatures have been recorded at locations in an area from Lancashire in the north, to Bristol in the southwest, and to London in the southeast of England. Since 1974 the temperatures have been adjusted to account for Urban Heat Island (UHI) effect. [1]

As an example of a CET recording station, Ringway in Cheshire was one of the original northern locations. There is record of Ringway chapel being used during the English Civil war (1642-1651). In 1723 the old chapel was replaced by a new red brick building and then demolished again and rebuilt as Ringway parish church in 1894.

Ringway, a typical rural location, was chosen as an airfield for Manchester and work began in 1935. The first aircraft landed at Ringway in 1937 on a partially completed grass landing strip. The first hangar was also completed in 1937. By 1938 a terminal building, control tower and other buildings were opened and Ringway Airport handled its first schedule flights with 4000 passengers in the first year.

In 1939 construction of RAF Ringway began on the north eastern part of the airfield with a further two new hangars on the south side and two more to the northwest. During 1941 two asphalt runways (3,000ft) were laid on an axis of 06/24 and 10/28. A further three large hangars were built between 1942/43 on the south side. Also in 1943 the runway 06/24 was extended to 4,200ft and a new 02/20, 3,300ft runway was constructed. During the war (1939-1945) there were seven main hangars and various smaller buildings.

After the war, between 1946 and 1957, although the RAF still maintained a squadron, Ringway was returned mainly for civil use. It was during this period when the airport had a large amount of growth. In 1952 the airport became a 24 hour operation with international and transatlantic flights. In 1954 the airport recorded its millionth passenger since the Second World War. 1962 saw the opening of a new £2.7 million terminal which incorporated Europe’s first “pier” system and in 1969 the runway was extended to 9,006ft. By 1978 more than a hundred companies operate at the airport employing more than 5,000 people.

In 1981 the runway was again extended, this time to 10,000 to attract long haul aircraft and by 1987 passenger numbers hit one million in a month. In 1986 a new world freight terminal opens and in 1989 a new Domestic Terminal with extra car-park facilities. During the 1990’s Terminal 2 was opened in 1993 along with a new railway station providing direct links to many towns in the North West. By 1995 passenger numbers reached 15 million per annum.

A new second runway was completed in 2001 and new upgrades to Terminal 1 and extensive development of Terminal 2 in 2003. 2007 saw another major refurbishment of Terminal 1 and a new Terminal 3. In 2008 the Concord conference centre was opened.

Throughout all this development many car parks, hotels and other operational and ancillary building were developed.


Fig 1 growth of Manchester Airport aircraft movements and passengers

There are a couple points to note from Fig 1; the rate of passenger growth has increased more than aircraft movements indicating more passengers flew on larger planes or increased fill capacity of existing planes; the rate of growth is in line with all the other airports in the UK as seen in Fig 2.


Fig 2 UK total aircraft movements since 1956

It is interesting to see in both Fig 1 and Fig 2 the decline in air travel from its peak in 2005.

From the history of Manchester airport development it is obvious the infrastructure has expanded enormously from being virtually a field with a landing strip in the 1930s to a major international airport today. This makes Manchester airport a good example of where Urban Heat Island effect occurs. However there is not a comparable rural site in the vicinity to measure the difference.

In a paper in “Weather” in December 2009 Dr. Philip D. Jones [2] compared various sites in and around London to determine the UHI effect. The paper compared two sites in the centre of London, St James Park and London Weather Centre with more rural sites of Rothampstead, and Wisley. Comparisons were also made with Kew and Heathrow dismissing Gatwick and Stansted. The argument for excluding the latter two were on the ground that they have not been run by the Met Office, but by the Civil Aviation Authority since 1990 and “only sporadically enter the Met Office database”. Out of interest CAA observers are all trained by the Met Office and the data for both has been completely available, I have been collecting hourly Gatwick data for 15 years.

In the conclusions he states; “UHIs have increased and urban-related warming has occurred at Heathrow and Kew sites located on the periphery of London. At Heathrow, mean temperature increased by 0.4 degC between the start of the record in 1949 and 1980. Since 1981 there has been no further increase in the UHI. It is expected that other sites located in the outskirts of Central London (like Heathrow and Kew) would show similar courses of change in their UHIs over the twentieth century, but sites within Central London would show no urban-related warming trends (i.e. constant UHIs) compared to rural stations around London.”


Fig 3 Met Office recording site Heathrow (courtesy Google Maps)

Not only is the Met Office recording site at Heathrow situated (not moved since 1949), in very close proximity to; a busy road (Northern Perimeter Rd W), to the north, east and west by car parks, to the south by tarmac and concrete taxiways and 500m from the main terminal complexes (T1, T2, T3) but also one of the worlds busiest runways (27R/09L) 200m away. Latest records (2011) shows there are 652 aircraft using this runway every day. The recording site is very close to where aircraft are at maximum thrust for take off or reverse thrust for landing emitting large amounts of heat energy.


Fig 4 an aerial picture of Heathrow (courtesy of Google Maps)


Fig 5 an aerial picture of Gatwick (courtesy of Google Maps)

When comparing the aerial pictures Fig4 Heathrow and Fig 5 Gatwick, visually it shows Heathrow as considerably more urban than Gatwick which is more rural just by observing the amount of vegetation (green) in the vicinity of each. Both airports are 0m above sea level and hence no temperature adjustment for height differential would be necessary.


Fig 6 Heathrow vs Gatwick maximum temperatures DegC


Fig 7 Heathrow vs Gatwick minimum temperatures DegC


Fig 8 Heathrow vs Gatwick average temperatures DegC

Over the last 11 years Gatwick is consistently cooler than Heathrow as shown in figures 6, 7 and 8.


Table 1 difference in temperatures between Heathrow and Gatwick

These examples, as in Table 1, are of course comparing a more urban site at Heathrow and a less urban site at Gatwick. But Gatwick, as with most airports has expanded in its infrastructure over time and, has its own level of UHI. The UHI difference between Heathrow and Gatwick is 0.8°C and assuming Gatwick has a similar UHI to a true rural site of 0.8°C then it shows the potential UHI in 2012 at Heathrow is 1.6°C and not 0.4°C (mean value) as suggested in the conclusion of the paper by Philip Jones.

Anecdotally, when driving through large towns and cities the temperature on the car thermometer invariably rises at least 2°C from the rural areas. And even the BBC weather forecasts suggest the countryside will be “a few degrees cooler” in certain situations.

A true rural site, which of course doesn’t exist, because, even at rural sites there is natural vegetation growth in the vicinity of recording equipment (trees, bushes etc), which changes the temperature profile of the location.

Many land surface recording stations used for temperature data are obtained from airports, mainly for historical reasons that Meteorological recordings were and still are necessary for the aviation industry. Is a true UHI adjustment made for these sites?

The conclusion of this investigation suggests that UHI adjustments for instrumental readings used in temperature reconstructions are not robust enough to provide high-quality accuracy.

Photosynthesising organisms used as temperature proxies:

In order for photosynthesis to occur, all trees and other living organisms (alkenone/phytoplankton) need specific amounts of air (gases), heat, light (photons), and water. In other words, no air (gases) a tree can’t form a tree-ring, no heat a tree can’t form a tree-ring, no light a tree can’t form a tree-ring and no water a tree can’t form a tree-ring. It is a combination of weather elements which assists a tree’s growth and the formation of tree-rings.

But to produce a tree-ring, a tree also needs a biological mechanism to control the uptake of specific essential nutrients, necessary for growth. However, the levels of air, heat, light and water are continuously changing. It is therefore necessary for this biological mechanism to cope with different levels of oxygen/CO2, hot/cold, light/dark and wet/dry. As such the biological mechanism is a weather-coping mechanism. The weather-coping mechanism is also a genetic switch on/off mechanism, a homeostasis regulator and a biological clock.

This part of the discussion paper will compare a specific combination of weather elements (air, heat, light and water), which will be referred to as a Photosynthesis Index (P-Index), with temperature alone. The P-Index has a range from 0-100. Photosynthesis is triggered around 6.9 but varies as each individual species has evolved its own level of tolerance to the combination of input stimuli (air, heat, light or water).


Fig 9 14 year comparison between daily maximum temperature (Tx) and photosynthesis P-Index a UK location

The comparison between maximum temperatures and the photosynthesis index (Fig 9) produces a correlation of +0.69. However, when Tx lowest to highest vs P-Index is compared a different story emerges as seen in Fig 10.


Fig 10 Tx lowest to highest vs P-Index

Fig 10 shows all temperatures up to and including 23°C can have a P-Index value of 0. Photosynthesis does not occur at 0 PI. In terms of photosynthesis trigger of 6.9 can be explained more clearly in Table 2.


Table 2 comparison between Tx and P-Index min/max

From the 14 years daily record, comparing Tx and P-Index (min and max) and considering a trigger point of 6.9 PI for full photosynthesis. Most trees will not start forming tree-rings until the temperature is about 7.5°C. The most important point to note is that photosynthesis on occasions does may occur in the temperature range between 7.5°C and 27°C.


Fig 11 frequency of days when photosynthesis occurs

From the analysis of the 5114 days for a UK location there are 4125 Tx days when photosynthesis could occur but only 1600 PI days when full photosynthesis does occur. In other words there are 2525 days out of 5114 days (49.9%) when tree-ring growth is not a good proxy for temperature reconstruction.

This investigation cast doubt on the use of tree-ring proxies as valid temperature reconstructions.

[Latest: The recent Marcott et al paper with their use of alkenone data (produced by phytoplankton) is likely to run into the same level of doubt (apart from the badly applied statistical analysis) as other living organisms such as tree-rings!!!]

Ice-Core Proxies:

Not enough expertise to comment!


A very simple analysis of comparison between temperature and CO2 shows little correlation between them. [more data would be necessary to conduct a proper study].


Table 3 average temperature, CO2 and relative humidity for Hawaii


Fig 12 Temp avge vs CO2 vs RH Hawaii

Correlations show -0.23 between Ta and CO2, and -0.08 between RH and CO2, both of which are not statistically robust.

CO2 levels at present are 390 parts per million of the atmosphere (0.039%), which includes water vapour and other GHGs. The natural carbon cycle produces 2960000m tonnes CO2 [3]. Mankind’s contribution is understood to be 33500m tonnes [4] which equates to 1.13%. The UK contribution of 458.6m tonnes [5] equates to 0.0155%. Therefore the total atmosphere (all GHG) is 2960*0.039%*100=758974358974m tonnes

So, the UK’s CO2 percentage of global atmospheric gases is: 0.0000000604%


It would appear that historical data, temperature proxies, used in climate change analysis are not robust enough to provide an accurate temperature reconstruction. I suggest the adjustment for UHI is too small, and tree-ring proxies don’t provide accurate temperature reconstructions.

As to the relationship, and assumption by climate scientists, between temperature and CO2, albeit on a very small sample just doesn’t show significant correlation. Has anyone conducted an in-depth study, using significant data, comparing temperature and CO2? Oh, yes use historical Hawaii temperature record, all 13 reporting sites in Hawaii Islands, are located at airports. Pick any one and it will have UHI effect. Show population growth and resulting infrastructure increases, oops more UHI effect. But what would we be comparing, CO2 levels versus real temperature or CO2 versus UHI temperatures? On one side of the fence “real temperatures” very low correlations. On the other side of the fence, MAN-MADE GLOBAL WARMING.

On a final note, the lack of knowledge, accepted by the IPCC, of cloud and water vapour effect on radiative feedback is interesting. Have a look at any global satellite picture in IR, Visual and Water Vapour (Fig 13) to see the importance of these two factors for climate research. Yet the IPCC knowledge in their chart from the third assessment summary shows their knowledge level as being very low. The P-Index (a combination of air (gases), heat, light and water) shows a correlation of 0.69 vs Tx (daily data covering 14 years) which is statistically significant. But look back at the effect on photosynthesis and tree-ring growth, and for that matter any living organism which photosynthesises.

Perhaps the P-Index might be a more reasonable indicator of radiative forcing, and temperature response, as it would act like photosynthesis.

In conclusion; current knowledge levels of the climate are not robust enough for the political decisions which are being based on this understanding. The political decisions with regard to the Climate Change Act and Energy policy are based on dubious science tantamount to homeopathy.



2. Jones P. D., Lister D. H. The urban heat island in Central London and urban-related warming trends in Central London since 1900, Weather, December 2009, Vol. 64, No.12


4. G.P. Peters et al. Global carbon budget 2010 (summary), Tyndall Centre for Climate Change Research


Mid-IR/Water Vapour 18Mar2013 1200 Vis Green/Red 18Mar2013 1200 IR 18March2013 1200

Fig 13 Satellite Pictures in three spectrums

All pictures courtesy of Dundee Satellite Receiving Station, copyright EUMETSTAT NERC.

25 thoughts on “Revisiting Temperature Reconstructions used in Climate Change Modeling

  1. I am no scientist but is there an alternative to taking the CET , identifying the the encroaching UHI and applying adjustments ? Would any knowledgable on WUWT person be able to identify a record that has always suffered the UHI effect and to use that as a benchmark ? unadjusted, because there is no need to adjust it

  2. ‘The political decisions with regard to the Climate Change Act and Energy policy are based on dubious science tantamount to homeopathy.’
    Isn’t this ironic. Quite apart from the errors and misconceptions in the above piece (congratulations deserved especially for the meaningless ‘UK’s CO2 percentage of global atmospheric gases is 0.0000000604%’), I’ve just been reading the ‘science’ behind Neil Catto’s Weatherology. ‘Weathergenes’. Ahem.

  3. Neil
    Useful article , thank you.
    I have written a number of climate related historical articles using CET amongst others datasets
    Here is the graph again that you quoted in the article
    It shows the considerable decline in temperatures in the UK over the last decade.
    My Reconstruction to 1538 shows some similar temperatures to today
    It came from my article here.
    Section 3 describes CET in some detail
    What is interesting is the small amount of UHi that is factored in, as described here from the article;

    “The geographic triangular area described is a heavily populated area of the country. In a private email to the author the Met office described the amount of UHI as follows;
    “The urbanisation corrections to the CET series have been applied since 1974. Initially they were just 0.1 degree C, in certain months, then gradually for more months of the year; from about 1995 onwards some of the corrections increased to 0.2 deg C, and by about 2002 all the corrections were 0.2 deg C.
    The above applies to Mean CET. The urban heat island effect is much more noticeable for minimum temperatures than for maximum, so for the Minimum CET series the corrections are double those for Mean Temperature, whereas for Maximum Temperature it was deemed in fact that no correction was required.”
    Britain is the size of New York state apparently and someone once described us as one large urban heat island. What would be interesting is if someone with the necessary skills could definitively determine if the 0.1C to 0.2C UHI factor is realistic or if it needs to be amended. Another one or two tenths of a degree downwards would put the modern temperature as just another hump in the road rather than a slightly larger than normal hill if we look back to 1538.
    Presumably it would not be less than 0.2C or the Met office would have used a lower calculation.
    Once again, thanks for the article.

  4. The significant amount of voluntary time invested by Neil Caito to produce his concise study backed by factual arguments is yet another example of how we “non-believers” feel the need to become totally emersed in the fight against the warmist’s assumptions. Like many, I too am totally obsessed with disproving AGW, spend far too much time scouring journals, researching evidence, and establishing the truth. I am gradually coming to terms with my neurotic need to continually debate the the miniscule level of CO2 with friends and family – instead of redecorating the lounge, fixing the garden shed or completing my tax return on time!
    So, looking at the “Cause & Effect” of introducing bad policies, ie. More smokers are dying of hypothermia than lung cancer. Now, due to the world’s unrealistic climate change policies, the resulting imposed legislation, energy subsidies, grants, carbon tax, and the ensuing financial chaos around us, if we’re not careful, the total combined ‘heat energy’ now being generated by us sceptics (as we frantically – and often angrilly – scribble notes down and publish papers to disprove AGW) will be the reason why the planet is warming up after all. Gore was right. It is our fault.
    Well done Neil. Good report.

  5. It might help to point out that the ICAO code for London Heathrow is EGLL, and for Gatwick is EGKK. Therefore the “LL” referred to in the graphs is Heathrow, and the KK is Gatwick.

  6. The oldest meteorological station is in Florence where the meteorological instruments – thermometer, barometer, hygrometer, anemometer and pluviometer were invented or perfected(
    Some of the oldest stations with a continuous records are Uppsala (Sweden) that started in 1722, Clementium (Orague Czech_ that goes back to 1752, as well as Berlin and St Petersburg, whereas the oldest in the USA is Milton MA that only goes back to 1885. De Bilt (Holland) dates back to 1706, though there have been several site moves and the current record is a compilation of several stations like CET. The best long run station on one site that links to solar activity and ocean oscillations is Armagh that goes back to 1796.
    The CET record covers several climate zones and so, IMHO, is not as valuable as claimed. Climate is reflected in the crops that can be grown and the CET stations range from cereals to grassland. The best record in the series is Rothamsted that is a long run record from the famous agricultural station and so has good data. However, it also suffers from an uncorrected UHI effect as the population increased rapidly after 1940 and it is close to motorways, Luton airport and the large town of Harpenden. Some of the current CET sites do not meet WMO standards:
    There have been 15 stations that have contributed to CET over the whole series with seven since 1958, the last two changes in 2004 (Stonyhurst for Ringway) and 2007 (Pershore for Malvern). This means that two of the four stations are now close together in Lancs and Pershore is a growing village area with thus a high UHI. Note also that these stations lie in different UK climate zones:
    Also other comments on CET and its contributing stations:
    Note: Squires Gate is only a Class 3 site at an airport:
    Note that many of the CET sites do not meet WMO standards as they are in distinct heat island areas
    Only Malvern of the CET stations is in a blue area with Oxford and Cambridge in green areas, Rothamsted in a yellow area and Ringway in a yellow/red area – as is Squires Gate.
    Many of these records have been examined by Frank Lansers in his Ruti project that gives a different view of the temperature series to CRU and GISS and which do not support the claimed global warming trend of the IPCC (

  7. I accept your conclusion (current knowledge not robust enough for polictical decisions) but have some difficulties following all of your arguments. The UHI discussion was reasonable easy to follow but the discussion of photosynthetic organisms and CO2 comes across as juvenile and poorly explained.
    What precisely is the photosynthetic index, is a reference available, or is this your own construct? – google provided no clear reference. I am trained in forestry and plant biology but admit I may be outdated a bit. If it is your own construct, more explanation is required for how it is calculated, how the threshold of 6.9 is determined, and what validation or support their is for that number. It seems much simpler to just say that tree rings (for example) are sensitive to multiple variables, and there are clear thresholds where growth is limited to non-existent (e.g. drought), regardless of temperature, and supported by references which are widely available in the literature. I also wonder if the following statement has a typo – should “may” actually be “not”?
    If I am reading this correctly, the very odd attempt to correlate local temperature and RH (Haiwaii) with CO2 leaves me baffled. Has anyone suggested such a localized correlation exists? How does demonstrating a lack of local correlation prove or disprove anything that is at argument? From my perspective it seems you either ran out of time/space to give CO2 a full treatment or should have provided the same answer as Ice cores “not enough expertise to comment”

  8. Soos says:
    April 16, 2013 at 5:13 am
    “… the errors and misconceptions in the above piece …”
    Could you please document the errors and misconceptions in the above article, so that we “lay” people reading this can fully understand where Mr Catto is in error. What he says all seems eminently reasonable and logical to me.
    If you cannot document this, with links to your sources, then you just a troll with nothing of value to add to any discussion.

  9. When Phil Jones, et al, set about whittling hockey sticks, they are all too aware of the places to NOT make proper adjustments….hey….you take your upticks where ever you find them. In Monforts “The Hockey Stick Illusion”, he notes that ring growth is a bell curve with temperature. Since there is a maximum growth temperature, that is less than local maximum, there are in fact, two possible temperatures for most ring growth widths. The hockey hoaxers always chose the temperature that fitted the stick. In addition, precipitation and insect/grassing animals had larger ring width influence. Ice cores suffer from a myriad of proxy defects as well. However, Anthropology does not LIE. Where, when and how our ancestors survived a constantly changing climate is the most indisputable record that there is on human impact, and human response. Minor changes in atmospheric trace gas levels are NOT a problem that needs solving.

  10. Thank you for the article, the temperature part was enlightening. I’m not so sure about the CO2 part though, I guess more detailed research is needed for that as CO2 and temperature mixing involve two rather different mechanisms (CO2 is not transported by radiation, for instance). What comes on my mind is a post on Tallbloke’s which seems to provide an interesting correlation when a delay is introduced:

    Not sure what a discussion of the impact of man made CO2 emissions has to do with homeopathy. I wonder if the author has a deep knowledge of homeopathy from intensive study or whether he is just paying homage to the “consensus” against homeopathy. “Climate change” is only decades old and in its infancy whereas homeophathy dates back centuries and still have dedicated supporters worldwide. Furthermore the supporters of homeopathy are not about to confine particularly the EU to the stone age like CAGW supporters are the way current policies are being pursued i.e. wind and solar power as well as greenhouse taxes on industry and private power consumers.
    Keep homeopathy out of the debate and keep the focus on daft climate change promotions and their dire consequences for us all.

  12. Where Climate Science has gone off the rails is the statistical assumption that climate is Gaussian. Climate is a fractal, which has led Climate Science to underestimate the probability of extreme events being natural. An interesting paper discusses the implications.
    A. M. Selvam
    Deputy Director (Retired)
    Indian Institute of Tropical Meteorology, Pune 411 008, India
    “The Gaussian probability distribution used widely for analysis and description of large data sets is found to significantly underestimate the probabilities of occurrence of extreme events such as stock market crashes, earthquakes, heavy rainfall, etc. Further, the assumptions underlying the normal distribution such as fixed mean and standard deviation, independence of data, are not valid for real world fractal data sets exhibiting a scale-free power law distribution with fat tails. It is important to identify and quantify the fractal distribution characteristics of dynamical systems for predictability studies.”

  13. This means that my annual contribution to global CO2 is an unforgivable 0.000000000000001%. Phew! I’m going to do the right thing end it all right now by drinking myself to death. Cheers! Is this where I say “sarc off”?

  14. Sorry Frank a slip of the fingers – it should be Lasner. Also the graphic in my post have not appeared but can be found at the references.

  15. MJB
    Thank you for your comments
    I am sure you will agree that it takes more than temperature alone to trigger photosynthesis. When I collect hourly weather data (daily) I use five of the parameters which include air (gases), pressure, temperature, light, and water to compile the P-Index. These are the main combinations which trigger photosynthesis. My point with tree-ring proxies is shown that although there are 4125 days when the temperature would indicate photosynthesis could occur but there were only 1600 when it explicitly would occur, this would affect the size of a tree ring.
    As far as juvenile is concerned, this is a post not a scientific paper and is positioned for as many people to understand as possible.

    I take this to mean that the Central London UHI effect has been constant during the 20th century whereas stations on the outskirts would show an increasing UHI effect as they have become more incorporated into the urban fabric. Is this reasonable? Traffic in Central London has been increasing at least till the advent of the tax, while buildings have been getting higher and higher. As a result of the increase in the height of buildings, I would expect winds at ground level to have generally decreased, so less heat has been carried away by the movement of the air. How much this effect may have been is anyone’s guess.
    Surely lighthouse keepers maintain met records, which may include temperatures? If so, I would nominate Lizard, Longships, Bishop Rock, Lundy or Wolf Rock as perhaps the met stations least likely to have experienced a UHI?


  18. Has anyone ever studied the effect of temperature on photosynthesis in a lab? My highschool biology tells me that plant growth depends on radiation, CO2, and water. As long as the water isn’t frozen, the tree will grow.
    No doubt there is a relationship between tree rings and annual temperatures. Why else would climatologists be using them as proxies? I believe that they assume that this effect is due to changes in the length of the growing season, but I have never heard of that assumption being tested. It seems odd that a trivial change in temperature would have such a dramatic effect.
    There are at least two other potential mechanisms which might explain this relationship. The calibration period for most of these proxies has been over the last century of recorded temperatures. During that century, temperatures have been gradually increasing, as have tree ring widths and densities. But so has CO2. If the general increase in CO2 levels has been causing the thicker trees, then the apparent correlation with temperature is a coincidence. This might also explain the Divergence Effect, where ring widths stopped increasing after the 70’s. If the CO2 levels have reached a level where trees are no longer starved for food and are limited by other factors such as water and sunshine, then the correlation with temperature falls apart.
    The other reason for a spurious relationship between temperature and photosynthesis might be sunshine. Plants grow faster on sunny days, and sunny days in summer are generally warmer.
    There are probably many other confounding factors, which suggest that we are a long way from being able to use trees as thermometers.

  19. We’d just landed at Gatwick on 9-11. Got to spend a week at the airport hotel before they let us fly back. Despite all the concrete, it’s definitely in more rural surroundings than Heathrow.

  20. @NeilC
    Thank you for the reply. First my apologies for the “juvenile” term. Looking back at my comment I can see it clearly comes across as insulting which was not my intent. My poor use of the term was meant to read “not fully developed” as opposed to childish or other less desirable interpretations.
    Your point on triggers of photosynthesis and influence of more than just temperature on tree ring width makes sense to me and aligns with my limited understanding of the natural world. What I am curious about is the specific ideas you are offering using the P-Index. If you could kindly provide a brief description (or reference) of both the index and how the threshold was determined it would be greatly appreciated.

  21. Gnashing teeth, hair pulling, straining at gnats will not serve science well. Every time I see posts like this one, one can only conclude that while these efforts may be laudable, they miss the entire point.
    Field scientists have, for over a century, solved many of the problems of accuracy in field observation. Their solution is random samples with adequate replicates to control for errors and bias. Until climate observations meet these minimal requirements, the data produced by non-random, non-replicated observations are simply TRASH & pseudoscience. Attempts to point out that such observations have this or that problem, while likely correct are misdirected.
    Furthermore, as ferdberple says: April 16, 2013 at 7:33 am
    data drawn from chaotic systems may not even be amenable to virtually any statistical data analysis since the data behavior may not meet simple assumptions required for such analysis even with proper replication and random sampling. The noise in the system clearly overwhelms the purported “climate signal” whatever that is supposed to mean.

  22. It’s worth repeating a comment I made in an earlier thread.
    Unfortunately Armagh Observatory was heavily affected by coal and peat burning in Armagh Town. This is from the 19th century.
    In his Foreword to the Armagh Catalogue2, Robinson had some hard things to say about the general siting. The prevailing west to south-east winds, he complained, were apt to “drive smoke from thousands of chimneys from the town over the Observatory, and interfere, by heated air, for nine months out of twelve”.
    A state of affairs that persisted until the 1980s. Minimum temperatures usually occur after dawn, when incoming solar radiation exceeds OLWR. Smoke reduces early morning incoming solar radiation and hence decreases minimum temperatures.
    Armagh minimum and average temperatures are probably most useful as a proxy for coal and peat consumption in Armagh Town.
    Armagh is just a small country town, with no industry to speak of. Smoke levels would have been much higher across central England. The area north of Birmingham is stilled called the Black Country from the time everything was coated in soot.
    While UHI and airports get most of the attention, they are far from the only local to regional scale anthropogenic effects on temperatures.
    CET is also probably most useful as a proxy for coal consumption.
    Dudley Horscroft says:
    April 16, 2013 at 8:37 am

    I’ve also proposed using temperature data from lighthouses, as these are likely the records least contaminated by local/regional anthropogenic effects, and therefore most likely to shown global effects.

  23. The impact of soot and smoke affected most of the long run temperature records until smoke abatement regulations came into play in the 1960’s in the UK and elsewhere. This would have affected CET more than Armagh, not least because the wind direction in N Ireland is not from the direction of Belfast:
    Frank Lasner with his Ruti project has found differences between coastal and inland stations on the plain or at elevations. Armagh is an inland station whereas CET is a mixture of all three types, such that Armagh provides a more consistent record.
    Of greater concern with these long run records are the changes in instruments, recording height and situation, most of which problems still persist in the modern – record as Anthony has amply pointed out with his surface stations studies. These problems are covered by Tony Brown in his essay in which he also refers to the earlier work of von Hann, many of whose criticisms are still valid today:
    To rely on any of the station records to provide the claimed change in global temperature of 0.8 oC or so since 1880 as a basis for the changes demanded by the IPCC is an act of folly, especially now that the Sun has entered a quiet phase that is likely to lead to a cooling cycle. As I have remarked before, climate is zonal not global and the only valid use of the temperature records is on a zonal basis and then in relation to what they were intended for, as a guide to crop production, and not as the newer stations are sited as a tool for pilots.

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