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Heat Island At Heathrow

July 14, 2015

By Paul Homewood


I thought I would take a look at temperature trends at Heathrow Airport, since records began in 1948, and compare them with the nearby site at Oxford. The results are astonishing.


The trend in annual mean temperatures at Heathrow since 1948 has been 0.027C/year. Now contrast with Oxford, which is 47 miles to the west.


The trend at Oxford is 0.020c/year, about a quarter less. Put another way, Heathrow is warming at a rate of 0.7C per century more than Oxford.

The weather station at Oxford is in the garden of Green College, but is still not totally unaffected by UHI, as it lies in within the bounds of the city of Oxford.

The Radcliffe Meteorological Station


Radcliffe Observatory, Oxford


Heathrow, of course, has grown out of all proportion since it began civil operations in 1946, as little more than a grass field with a few propeller planes carrying 63,000 passengers. Last year, more than 73 million flew from Heathrow.

Of course, it could be that there are genuine climatic reasons for the warmer trend at Heathrow, even though Oxford is only just up and the road, and both are inland sites. However, the probability that the heat island at Heathrow is responsible is much strengthened when we look at the Central England Temperature trends, which is based on the Midlands region bordering on Heathrow.


We actually find that the trend of the CET is less even than at Oxford, 0.014C/year. This would suggest that maybe half of the warming at Heathrow has been caused by the heat island.

Much of the temperature data used for global calculations these days come from airport sites, pretty much all of which have developed from small operations, usually just after the war. Though most don’t approach Heathrow in size, this analysis suggests that heat island at airports is a significant factor which may not being taken into account.

Regardless of the global implications, it clearly makes a nonsense of “the hottest UK July day” claim.

  1. 1saveenergy permalink
    July 14, 2015 5:25 pm

    Paul, bad boy, you shouldn’t take “the hottest UK July day” away from them,

    what else have they got to believe in !!

  2. July 14, 2015 5:31 pm

    At first glance, the trends “look” similar, but or course when you actually do the calculations they aren’t.

    A simple question for the Met. Office. Why is the trend at Heathrow almost twice that of CET, if not due to the UHI effect?

    Clearly the observed temperature at Heathrow cannot be relied upon.

  3. July 14, 2015 5:34 pm

    It might be useful to show the trends on the same graph, with the same vertical scale.

  4. Bloke down the pub permalink
    July 14, 2015 5:35 pm

    It makes you wonder if the proposed third runway at Heathrow will be given the go-ahead just in order to keep the trend heading in the ‘right’ direction. Now that really would be one for the conspiracy theorists.

  5. Don Keiller permalink
    July 14, 2015 5:58 pm

    Methinks another letter to the Met Orifice is in order.

  6. Joe Public permalink
    July 14, 2015 6:20 pm

    To put Heathrow’s development into perspective – “March 1946:….The passenger terminal was an area of Army tents ….”

    WikiP also informs that by 1953 when there were a total of 62,000 flights for 1 million passengers. [c.f. 2014 when there were 470,695 aircraft movements]

  7. July 14, 2015 6:42 pm

    This article and others before is proof, at least to me, that the effect of UHI is not being properly accounted for by the Met Office.

    • Ben Vorlich permalink
      July 14, 2015 9:59 pm

      Yes I agree, and in all the non-satellite data.

  8. July 14, 2015 7:59 pm

    UHI and its relevance to the climate debate is a potential gold mine of information and perspective. UHI is not fully and properly investigated anywhere as far as I can see. More genuinely rural data sites are needed. The relationship between population and temperature is not likely to be a simple linear one and is confounded by many variables such as population density, height of buildings, narrowness of streets, numbers and types of vehicles and other machinery, etc. Each are likely to contribute in different ways.

    • July 15, 2015 9:00 am

      Particularly the materials used in road and building construction and their colours.

  9. July 14, 2015 8:00 pm

    I wonder if they record wind speeds near planes landing and taking off?

    • Dave Ward permalink
      July 15, 2015 11:00 am

      Yes – that’s just as important to pilots as the temperature. A whole load of parameters are fed into a modern passenger planes FMC (Flight Management Computer) as the crew are preparing for the flight. The outcome will determine if there is sufficient runway available for a safe take-off, in that particular situation. A change in wind direction and/or speed might necessitate an alternative runway or direction being requested. There are some locations notorious for having completely different conditions at each end of the runway, which makes for tricky planning!

  10. 1saveenergy permalink
    July 14, 2015 8:12 pm

    Any idea what plane movements were happening at the time near the recording station at Heathrow ???

    • Ben Vorlich permalink
      July 14, 2015 10:02 pm

      You could try here, both Heathrow and Gatwick

    • Ben Vorlich permalink
      July 14, 2015 10:03 pm

      You could try here for data on both Heathrow and Gatwick

    • Ben Vorlich permalink
      July 14, 2015 10:05 pm

      Sorry about double posting

    • Joe Public permalink
      July 14, 2015 11:01 pm

      Approx 1 every 45 seconds; plus a number queuing on the taxiway to take-off, and, also some after landing.

      • saveenergy permalink
        January 6, 2016 12:58 pm

        Real time aircraft movements at Heathrow –,-0.46/13

        (Hover cursor over plane for its call-sign, click for full details. You can drag & expand map to give the whole worlds commercial aircraft positions & identify each one. Times out after 30min, just reload page.)

    • Ben Vorlich permalink
      July 15, 2015 5:30 am

      From the link I gave last night here are the 12:30 -13:30 flight data. 4th column plane type and 6th time

      Heathrow 01/07/15
      BAW940 BA940 GEUPJ A319 EDDL 1230 521 09R
      UAL914 UA914 N677UA B763 LFPG 1231 257 09L
      AAL105 AA105 N726AN B77W KJFK 1231 342 09R
      BAW45EM BA459 GEUXI A321 LEMD 1232 511 09R
      BAW816 BA816 GEUUR A320 EKCH 1234 508 09R
      BAW983 BA983 GEUPC A319 EDDT 1235 502 09L
      VIR6892 VS3022 EIEZV A320 EGPD 1235 226 09L
      VIR11B VS011 GVSXY A333 KBOS 1235 321 09R
      DAL36 DL036 N172DZ B763 KSEA 1236 408 09R
      BAW467 BA467 GEUYL A320 LEBB 1237 327 09L
      CASTLE6 SIG006 GGRND HELI EGGW 1237 457 H
      EIN16F EI164 EICPH A321 EIDW 1238 221 09L
      SHT7Z BA1483 GEUXF A321 EGPF 1239 505 09L
      AAL729 US729 N272AY A333 KPHL 1239 327 09R
      AIC130 AI130 VTANH B788 VABB 1240 403 09R
      SWR37M LX354 HBIPU A319 LSGG 1241 216 09L
      BAW107 BA107 GBNLP B744 OMDB 1241 537 09R
      BAW288 BA288 GBNLF B744 KPHX 1242 518 09L
      ACA861 AC861 CFCAE B763 CYHZ 1242 236 09R
      MEA202 ME202 ODMEB A332 OLBA 1243 329 09R
      AFR1780 AF1780 FGTAK A321 LFPG 1244 412 09L
      BAW9L BA093 GZBJF B788 CYYZ 1244 538 09R
      EIN03C EI034 EIEPS A319 EGAC 1245 224 09L
      BAW780F BA780 GBNWZ B763 ESSA 1245 513 09R
      BAW951L BA951 GEUXL A321 EDDM 1246 517 09L
      BAW177 BA177 GVIIS B772 KJFK 1246 541 09R
      BAW531 BA531 GEUYI A320 LDSP 1248 509 09L
      SWR33E LX332 HBIYS RJ1H LSZH 1248 246 09L
      ASL42J JU381 YUAPF A319 LYBE 1249 419 09R
      BAW438 BA438 GEUYW A320 EHAM 1249 522 09R
      BAW777C BA777 GEUPN A319 ESSA 1250 513 09L
      GWI6U 4U8462 DAGWH A319 EDDT 1251 220 09L
      SWR319 LX319 HBIJN A320 LSZH 1251 217 09R
      BAW71F BA284 GCIVA B744 KSFO 1252 541 09L
      UAL96 UA096 N26910 B788 KIAH 1252 246 09R
      ELY315 LY315 4XECC B772 LLBG 1254 403 09L
      SHT6R BA1484 GEUXD A321 EGPF 1254 502 09R
      BAW860 BA860 GEUYM A320 LKPR 1255 303 09R
      KLM1017 KL1017 PHBGQ B737 EHAM 1256 408 09L
      ICE451 FI451 TFFIO B752 BIKF 1256 241 09R
      BAW3ZL BA713 GEUPU A319 LSZH 1257 501 09L
      TAP359W TP359 CSTNM A320 LPPT 1257 220 09R
      BAW108 BA108 GVIID B772 OMDB 1258 543 09L
      BAW908N BA908 GEUPR A319 EDDF 1259 525 09R
      BAW974 BA974 GEUPL A319 EDDH 1300 509 09R
      BAW609 BA609 GMIDS A320 LIEO 1301 522 09L
      GWI464 4U464 DAGWD A319 EDDK 1302 219 09L
      DLH5U LH907 DAIUO A320 EDDF 1302 216 09R
      BAW9274 BA9274 E GEUUA A320 EGPH 1303 531 09L
      BAW836 BA836 GTTOB A320 EIDW 1303 506 09R
      SIA305 SQ305 9VSWJ B77W WSSS 1304 242 09R
      BAW34BQ BA541 GEUYH A320 LIPE 1305 519 09L
      VIR468C VS3004 EIEZW A320 EGPH 1306 223 09L
      BAW5 BA005 GSTBJ B77W RJAA 1306 556 09R
      UAL930 UA930 N784UA B772 KSFO 1308 241 09L
      AFL2579 SU2579 VQBNS A333 UUEE 1308 414 09R
      BAW85GA BA849 GEUUY A320 LDZA 1310 542 09L
      ROT391 RO391 YRASB A318 LROP 1310 401 09L
      EIN16L EI163 EIDVJ A320 EIDW 1310 223 09R
      GWI12X 4U7462 DAGWS A319 EDDH 1312 218 09L
      BAW872 BA872 GMIDY A320 EPKK 1312 503 09R
      BAW939 BA939 GEUOI A319 EDDL 1313 521 09L
      BAW396 BA396 GMIDT A320 EBBR 1313 523 09R
      BAW984G BA984 GEUYR A320 EDDT 1313 518 09R
      BAW84 BA084 GCIVE B744 CYVR 1314 533 09L
      BAW242 BA242 GBYGF B744 MMMX 1315 555 09L
      QFA10 QF010 VHOQH A388 OMDB 1315 305 09R
      BAW169 BA169 GSTBI B77W ZSPD 1317 555 09R
      BAW82 BA082 GCIVZ B744 DNAA 1318 567 09L
      BAW827 BA827 GEUUB A320 EIDW 1319 523 09L
      SAS532 SK532 SERJT B737 ESSA 1319 219 09R
      VIR45W VS045 GVWOW B744 KJFK 1320 322 09R
      BAW605 BA605 GEUXG A321 LIRP 1321 512 09L
      BAW287 BA287 GCIVC B744 KSFO 1321 566 09R
      SHT19P BA1311 GEUYP A320 EGPD 1322 503 09L
      BAW835 BA835 GEUUP A320 EIDW 1323 525 09L
      SHT12G BA1332 GEUYT A320 EGNT 1323 519 09R
      BAW485 BA485 GEUYN A320 LEBL 1324 309 09L
      AUA461N OS461 OELBX A320 LOWW 1326 217 09L
      EIN715 EI715 EIEDP A320 EICK 1326 221 09R
      BAW315 BA315 GEUUM A320 LFPG 1327 507 09L
      BAW347 BA347 GEUPA A319 LFMN 1328 508 09L
      DLH9KW LH2475 DAIPC A320 EDDM 1328 218 09R
      GWI13Z 4U2461 DAKNS A319 EDDS 1329 217 09R
      BAW729 BA729 GEUPW A319 LSGG 1330 509 09L
      AAL135 AA135 N728AN B77W KLAX 1330 336 09R
      BAW146 BA146 GMEDF A321 OJAI 1331 552 09L

      • 1saveenergy permalink
        July 15, 2015 10:34 pm

        Thanks Ben,
        I make that 87 plane movements happening in that hr, near the recording station at Heathrow, situated at the eastern end of the north runway [ just where engines are on max thrust for take off ] .

        the prevailing wind is from the southwest (4 o’clock on the map) so will blow hot gasses over the thermometers.

  11. July 15, 2015 1:31 am

    During the 2013 Jul heatwave resurfacing on Southern runway had to stop.
    Saw mention of 50°C somewhere! Jones et al 2010 worth a look but mostly UHI dismissed as not important. Strange seems to be found elsewhere



    Despite the presence of the North Sea and other large water bodies, UHI intensities at the different locations within the Rotterdam agglomeration can be substantial, under favourable meteorological conditions (i.e. under calm and clear weather conditions). Our results show that this is true for a large part of the year; only in winter, UHI-intensities are generally lower. The highest maximum UHI values are found in late spring and summer, with 95 percentile values ranging from 4.3 K to more than 8 K, depending on the location. These values are consistent with earlier observations in Rotterdam[22] and [23], and of the same order of magnitude as those reported for other European cities [41]. In addition, we find a substantial intra-urban variability in UHI intensity, indicating that local characteristics of the built environment have an important influence. It is interesting that also a UHI effect is found for the KNMI station at the airport. This can be explained by the plume effect of the built environment (see also Ref. [23]).

    Not sure on reliability of the method (see conclusions) but interesting nonetheless
    An evaluation of thermal Earth observation for characterising urban heatwave event dynamics using the urban heat island intensity metric
    Tomas Holderness*†, Stuart Barr†, Richard Dawson†, Jim Hall‡

    This screen shot from a London Assembly paper on UHI

  12. July 15, 2015 1:34 am

    Paul – comment in moderation due to number of links. Also you are being naughty comparing Oxford. If GISS taught you anything you need to choose a site a few hundred miles further away 😉

    • AndyG55 permalink
      July 15, 2015 4:06 am

      “few hundred miles further away ”

      Do you mean somewhere like in the middle of the Sahara? 🙂

  13. July 15, 2015 2:02 am

    Looking from sun side

    It’s a poor site.

    Google 2006 image nicely shows the sun shadow. been like that for years.

    The dominance can be seen here

    !945 Google image?
    Oddly I can’t make out the observatory.

  14. Eliza permalink
    July 15, 2015 2:43 am

    Sorry for being sarcastic but as Bart Simpson would say Duh?

    • July 15, 2015 5:36 am

      Shouldn’t that be Homer Simpson?

  15. arfurhaddon permalink
    July 15, 2015 6:31 am

    Just under the last graph “the trend of the CET is less even than at Oxford, 0.14C/year.”
    Is that right when the trend at Oxford is 0.020c/year? Should it be 0.014C/year?

    • AndyG55 permalink
      July 15, 2015 7:28 am

      Well caught.. 🙂 Obviously a typo was made.

      yep , the graph says approx. 0.014C/year

    • July 15, 2015 8:42 am

      Yes my boob!

      CET s/be 0.014C

      Thanks and updated

  16. Mark Hodgson permalink
    July 15, 2015 7:47 am

    Off subject, I know, but I couldn’t resist mentioning this morning’s news on the BBC website (posted apparently with a straight face by their industry correspondent under Business News, not under “Science & Environment”) headlined “UK spare electricity capacity to fall this winter”.

    I can’t find any mention of unreliable renewables in the article – apparently “EU regulations have forced older polluting power plants to close. Low wholesale power prices have continued that trend making some plants uneconomic to keep open.” Nothing to do with the uselessness of wind turbines and solar panels, then.

    To compound the mess, (or as the BBC reports it) “To ensure the lights stay on, for the second year running, National Grid will pay firms like Centrica and SSE to keep power plants in reserve. It is also paying large energy users, such as Tata Steel, to switch off.”

    You don’t have to be a Roger Helmer (UKIP’s energy spokesman) to see the madness in all this.

    The link to the article is here:

    By the way, Paul, please keep up your excellent work on UHI, historical extreme weather etc. It all helps to balance the constant bombardment of propaganda from the BBC and other MSM. If you could get a chance to post something about this morning’s BBC story (above), however, it might be useful, as your blog is now obviously being monitored quite widely and occasionally picked up by the MSM. You’ve obviously touched a nerve as well, judging by some of those comments from the alarmist community in response to the Telegraph article about your “outing” of the Met Office in relation to “that” Heathrow “temperature record”. Please maintain a thick skin, as ad hominem attacks remain the alarmists’ weapon of choice whenever they encounter an argument they don’t like and can’t deal with. And bear in mind that the more they attack you, the more you must be doing something right!

  17. Tim Hammond permalink
    July 15, 2015 9:28 am

    So Heathrow has built a new terminal and significantly increased the number of passengers, trains, cars, coaches and buses using the airport.

    Over the last few years the aircraft have got bigger – A380s, B737-800, A321.

    And there has been a switch between short-haul, smaller aircraft and long-haul larger aircraft, meaning the average size of aircraft has got larger.

    But apparently all this has happened without any impact on the temperature?

  18. July 15, 2015 4:53 pm

    I have just done a comparison of the difference between annual temperatures at Heathrow and Oxford which I find interesting.
    The 10 year rolling average difference has generally climbed from about 0.265c in 1957 to 0.548c in 1978, fell to 0.478c by 1988, increased again to 0.667c by 1998 and has stayed fairly static since.
    The greatest annual difference was +1.02c in 2003.

  19. July 16, 2015 7:55 am

    I think the most telling comparison is between Heathrow and CET, where the difference in annual temperature (decadal average) has increased steadily from 0.76c in 1957 to 1.53c in 2014.
    This is an increase of almost 0.77c over the period, which must represent the minimum artificial increase in temperature at Heathrow.

    • July 17, 2015 8:53 am

      I have now calculated the change in July temperature between Heathrow and CET, and found that the decadal average difference has increased from 1.35c in 1957 to 2.305c in 2014, an increase of 0.96c over the period.
      So it seems that the AHI (Airport Heat Island) effect is greater, and is increasing faster in July than the annual mean.
      Could this be a result of greater airport activity in that month?
      I hope to calculate the equivalent figures for all months when I have the time.

      • July 17, 2015 7:24 pm

        There seems to be a seasonal pattern to the differences between Heathrow and CET temperatures and to the changes to these since 1948, with the summer months showing the greatest difference and change.
        In the following table the first column is the 1948-57 mean difference, the second column is the 2005-2014 mean difference and the third the change.
        The changes for June & July are almost identical.
        There is a slight discrepancy between the annual figures calculated by this method and the figures I quoted earlier which were calculated using annual data. I have ruled out obvious errors so I put this down to rounding errors.
        MONTH 1957 2014 CHANGE
        JAN 0.240 0.930 0.690
        FEB 0.300 1.020 0.720
        MAR 0.635 1.330 0.695
        APR 0.905 1.825 0.920
        MAY 1.085 1.940 0.855
        JUN 1.345 2.295 0.950
        JUL 1.345 2.305 0.960
        AUG 1.310 2.080 0.770
        SEP 1.145 1.805 0.660
        OCT 0.680 1.385 0.705
        NOV 0.285 1.045 0.760
        DEC 0.240 0.960 0.720

        MEAN 0.793 1.577 0.784

      • July 17, 2015 8:09 pm

        Sounds like sunshine in summer has a disproportionate effect at Heathrow with all that tarmac.

      • July 18, 2015 8:06 am

        I wondered how the seasonality of temperatures at Heathrow related to activity.
        I found some stats on passenger movements for 2005-2014, and it seem that the peak month is July, followed by August, June and September.
        So assuming aircraft movements correspond to passenger movements, this pretty much ties in with the temperature differential, and change since 1948.
        Average movements in millions of passengers:
        MONTH MEAN
        JAN 5.10
        FEB 4.73
        MAR 5.59
        APR 5.67
        MAY 5.79
        JUN 6.17
        JUL 6.63
        AUG 6.48
        SEP 6.16
        OCT 5.92
        NOV 5.23
        DEC 5.41

      • July 18, 2015 8:18 am

        Sorry correction to movment stats. Previous Jan-Jun included 2015.
        MONTH MEAN
        JAN 5.07
        FEB 4.71
        MAR 5.56
        APR 5.63
        MAY 5.73
        JUN 6.12
        JUL 6.63
        AUG 6.48
        SEP 6.16
        OCT 5.92
        NOV 5.23
        DEC 5.41

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