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.
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. http://www.metoffice.gov.uk/hadobs/hadcet/ 
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  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!!!]
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 . Mankind’s contribution is understood to be 33500m tonnes  which equates to 1.13%. The UK contribution of 458.6m tonnes  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.