Why is Heathrow so hot?

Posted: August 2, 2018 by oldbrew in climate, Temperature, weather
Tags: ,

In the report ‘hottest day ever’ must mean ‘since the weather station was installed’, but we’re used to this kind of excitable exaggeration in BBC climate reporting. At least they are admitting the obvious here, that Heathrow has certain heat-related factors built-in.

It’s Europe’s busiest airport, says BBC News, and as well as attracting millions of passengers could Heathrow also be a magnet for the sizzling heat?

Heathrow holds the UK record for July’s hottest day ever. Three years ago it reached a sweltering 36.7C.

It also briefly recorded 2018’s highest temperature of 35C, before being pipped by Faversham (35.3C) in Kent last Thursday.

And last year the thermometer peaked at 34.5C at – you guessed it – Heathrow.

So what’s causing Heathrow to rise to the top of the temperature charts?

How is temperature measured?

To get a standardised temperature, a weather station, known as a Stevenson Screen, is used.

These white boxes, which contain a thermometer, are installed 4ft (1.25m) above the ground and are dotted all around the UK.

The weather station at Heathrow is located very close to the northern runway, so with aeroplanes constantly landing and taking off, does it make a difference to the temperature?

Not according to Paul Williams, Professor of Atmospheric Science at the University of Reading.

“Planes make a negligible difference,” says Professor Williams.

“Every time you use energy – whether it’s from a plane’s engine, or even just switching on a light bulb or taking a shower – it’s eventually turned into heat.

“But all of that is a minor influence compared to the effect of the urban heat island.”

The urban heat island is, Prof Williams explains, the process where buildings absorb more sunlight than open fields.

Cities tend to hang on to the heat for longer, which can push up temperatures by a few degrees, he says.

Heathrow – with its large black asphalt runways and airport buildings – will naturally absorb more heat.

Continued here.

  1. cognog2 says:

    “Every time you use energy it winds up as heat” Quite right.

    . So if you add up the global energy consumption whether by fossil, wind, solar, nuclear, biomass or whatever it contributes to warming the planet. Perhaps it is this that accounts for the very slight warming we find over the years?

    Fortunately for us water evaporates away this heat up into space via the Rankine Cycle. So we don’t have to worry. ( just like those cooling towers the Green blob likes to show us all the time)

  2. Bitter@twisted says:

    So these climate “experts” admit that UHI “causes a few degrees of warming”.
    Then they smear it across a load of other rural sites by “homogenisation” and then have the gall to tell us that it’s all because of CO2.
    Talk about Mann-made global warming!

  3. Phoenix44 says:

    I live in London ad used to work out at Heathrow. Winters it would be cold in London, freezing just outside, not freezing by the airport. One to two degrees back and forth.

  4. Bitter@twisted says:

    “Planes make a negligible difference” states “Professor” Williams.
    So this genius has never stood downwind of an idling passenger jet?
    You can just imagine the effect of this on a downwind temperature sensor.
    The professor is a moron.

  5. Bloke down the pub says:

    I understand what the prof means by ‘planes make a negligible difference’. He is talking about the energy put into the general environment and as he points out , the impact on temperature of covering the place in concrete and tarmac is far greater. What he chooses to ignore is when a jet’s efflux is pointed straight at the weather station, which most certainly can cause a jump in the reading.

  6. Ian W says:

    The automated observation station involved at Heathrow can be seen in the image:
    in the post on:

    What is not explained is the location of the sensor and the likely activity of the aircraft in relation to the sensor. You will note that the East West runway is just a few yards south of the observation station there are several right hand exits off the runway just by and beyond the location of the sensor. When an aircraft lands immediately after touchdown it will put its engines into reverse thrust and increase the throttle setting to close to full power this will dump thousands of cubic feet of exhaust with some of it above 600degC into the local air. Then having slowed to a safe speed the thrust reversers are stowed and the aircraft has to turn onto one of the exit taxiways to the South of the runway yet again the engines will be spooled up to turn the aircraft onto the taxiway and the jet eflux again with some of the air above 600degC will be directed right at the observation station.

    There was some discussion last year on the timing of the spike of Heathrow temperatures and it seemed to match with the arrival time of an A380. Of course this year the highest temperature at Heathrow was just pipped by Faversham that has an ice cream van parked next to its Stevenson screen venting its hot refrigerator cooling air over the sensors to keep the heat record in Kent.

    It must be remembered that the observations at airports are skewed by acres of tarmac and concrete and jet engines outputting high temperature eflux. The observations are useful for aircraft operations as the actual temperatures there are important for calculating the amount of thrust required on takeoff. However, including these readings into the country ‘climatological’ metrics makes no sense whatsoever.unless it is intended to deliberately skew temperatures warmer.

  7. ivan says:

    Where do they get the idea that a temperature of around 35C is ‘hot’? My weather station is showing a temperature of 39C at the moment and had a high of 41.2C on Tuesday and this in a rather sleepy village in France.

  8. oldbrew says:

    ivan – at least half of Britain never reaches 35C.

    Some parts rarely reach 25C.

  9. craigm350 says:

    Reblogged this on WeatherAction News and commented:
    From the article:

    Cities tend to hang on to the heat for longer, which can push up temperatures by a few degrees, he says.

    TonyB commented last year on UHI and CET;

    I use CET in my own reconstructions of historic temperatures, currently to 1538

    The met office are very helpful. I have met with David parker there who compiled Hadley CET to 1772 following on from manleys work to 1660. He subsequently sent me a variety of PDF’s regarding the location of the stations. I also met with Richard betts and have looked at Records in both the library and archives.

    Britain is a small place. Arguably with a population of sixty million crammed into a space the size of new York state, it could be argued the whole of our island Is potentially affected by uhi for the last century and allowance needs to be made for this, especially over the last few decades
    Ringway was the most obviously affected station beyond the 0.2 allowed for by the met office. I suspect that a substantially greater amount should therefore have been allowed for and this may have lowered the peak we saw in cet at the turn of the century.

    Hubert lamb once said about historic reconstructions that ‘we can understand the tendency but not the precision’ in other words it allows us to see the general trend but we should not expect to be able to parse temperatures to fractions of a degree.


    Instead of recognising this we quibble every year or so when a new record is set by a few tenths of a degree. There’s a reason many people avoid London on a really hot summers day and it’s not climate change.

  10. nickreality65 says:

    The Radiative Green House Effect theory contains a fatal flaw.

    For RGHE to function as advertised requires the earth’s surface to radiate upwelling LWIR as an ideal black body, i.e. at 288 K, 390 W/m^2.

    The contiguous presence of atmospheric molecules participating in heat transfer through conduction, convection, advection, evaporation and condensation renders impossible such BB LWIR, the effective surface emissivity being 0.16, 63 W/m^2.

    The LWIR upwelling 390 W/m^2 does not exist, the GHG energy loop “warming” the surface and atmosphere does not exist – and the global warming and climate changes attributed to carbon dioxide do not exist.

  11. ivan says:

    oldbrew, you have just reminded me of one of the reasons I left the UK over 30 odd years ago.

  12. pochas94 says:

    Of course, dark surfaces absorb and thermalize solar photons which generates heat and must be re-radiated at infrared wavelengths which are absorbed by greenhouse gasses near the surface. This certainly will affect near-surface temperatures. With higher albedo, more of the solar photons are reflected. The atmosphere is transparent to the reflected high energy solar photons so they are not thermalized and do not generate near-surface heat.

  13. oldbrew says:

    It’s misleading to talk about ‘how hot’ Heathrow may be when its mean maximum temperature for August (summer in the UK) is little more than 22C.

  14. richard verney says:

    With jet engines, it is not necessarily the exhaust heat, but rather the knock on consequence of the thrust. The Tarmac absorbs energy, and the Tarmac is often 10 degrees or more warmer than nearby grass. The warm air that is accumulated over the runways, is blown by the thrust of the jet towards the weather station, causing a warm wind..

    In the past LIG thermometers had a thermal lag/response time of around 1 minute. Today’s electronic sensors have a thermal lag/response time of fractions of a second. Further, very often the Stevenson screen is of a smaller volume compared to that used in the past. Once again resulting in faster response time.

    The upshot is that modern day measurements are bastardised by short transient bursts of heat which would have gone unrecorded in the past with old fashioned LIG thermometers.