World War II bombing raids offer new insight into the effects of aviation on weather

From Wiley-Blackwell via Eurekalert

Wartime weather records reveal impact of contrails caused by USAAF raids

This is a formation of B-17F Flying Fortress bombers of USAAF 92nd Bomb Group over Europe, circa 1943 . Credit: United States Air Force

Climate researchers have turned to the Allied bombing raids of the Second World War for a unique opportunity to study the effect thousands of aircraft had on the English climate at a time when civilian aviation remained rare. The study, published in the International Journal of Climatology, reveals how civilian and military records can help assess the impact of modern aviation on the climate today.

The research, led by Prof Rob MacKenzie, now at the University of Birmingham, and Prof Roger Timmis of the Environment Agency, used historical data to investigate the levels of Aircraft Induced Cloudiness (AIC) caused by the contrails of Allied bombers flying from England to targets in Europe. The team focused their research on 1943 to 1945 after the United States Army Air force (USAAF) joined the air campaign.

“Witnesses to the huge bombing formations recall that the sky was turned white by aircraft contrails,” said MacKenzie. “It was apparent to us that the Allied bombing of WW2 represented an inadvertent environmental experiment on the ability of aircraft contrails to affect the energy coming into and out of the Earth at that location.”

Aircraft can affect cloudiness by creating contrails, formed when the hot, aerosol-laden, air from aircraft engines mixes with the cold air of the upper troposphere. While some contrails disappear swiftly, others form widespread cirrus clouds which intercept both the energy coming into the planet as sunshine and that leaving the planet as infrared heat.

When the USAAF joined the Allied air campaign in 1943 it led to a huge increase in the number of planes based in East Anglia, the Midlands and the West Country. Civil aviation was rare in the 1940s, so USAAF combat missions provide a strong contrast between areas with busy skies and areas with little or no flight activity.

Today air travel is growing at an annual rate of 3-5 % for passenger aircraft and 7 % for cargo flights, but quantifiable data on the impact of AIC remains rare. In September 2001 United States airspace was closed to commercial aircraft following terrorist attacks, presenting scientists with a unique moment to study the effect of aircraft contrails in normally busy sky. Results from the 9/11 studies are controversial, but now MacKenzie and his colleagues have found an opportunity to study the opposite impact of contrails on the usually empty skies of the 1940s and have found that it is indeed possible to see the effects of AIC in surface weather observations, but that the signal is weak.

The study involved painstaking retrieval of historical records, both from the Meteorological office and from the military. The importance of weather conditions to the success of bombing missions meant that the Second World War prompted some of the most intensive weather observations ever undertaken but these are not all archived electronically.

B-17 Contrails

These are vapor trails as a flight of B-17's joins another flight for a long-range mission. Credit: Annette Ryan

To distinguish the effect of aviation more clearly, the team focused on larger raids from the many flown between 1943 and 1945. They selected raids that involved over 1000 aircraft and that were followed by raid-free days with similar weather which might be used for comparison. The resulting top 20 raids revealed 11th May 1944 as the best case study.

The team found that on the morning of the 11th 1444 aircraft took off from airfields across south east England into a clear sky with few clouds. However, the contrails from these aircraft significantly suppressed the morning temperature increase across those areas which were heavily over flown.

“This is tantalising evidence that Second World War bombing raids can be used to help us understand processes affecting contemporary climate,” concluded MacKenzie. “By looking back at a time when aviation took place almost entirely in concentrated batches for military purposes, it is easier to separate the aircraft-induced factors from all the other things that affect climate.”

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77 thoughts on “World War II bombing raids offer new insight into the effects of aviation on weather

  1. One point to note, is that the massed bomber raids concentrated the aircraft and thus their contrails in a discrete area. Civilian aviation is far more dispersed by the time the planes reach an altitude where contrails can form.
    Also, is there a difference between the exhaust gases produced by radial piston engines & jets? Will this lead to differing properties in the vapour trails formed?

  2. I think there’s a lot to learn from military archives from WWII.
    Just remember that the Nazi’s were able to infiltrate a few patrols in the Arctic (Svalbard, Iceland, Greenland), tasked to operate some meteo stations to collect data for the planning of military operations; the last Nazi station surrendered on September, 1945!
    And the same was made, on a bigger scale, by the Allies.
    After 1945, we have the full time lenght of the Cold War, with the planning of naval operations in the GIUK (Greenland, Iceland, United Kingdom) theatre of operations, the NORAD and so on.
    Well, IMHO, I think there’s still a LOT to discover and to learn from military archives…
    Just my 2 cents
    Dario

  3. I remember seeing a program about the 3 days after 9/11 when all planes were grounded.
    A guy at a weather station somewhere in the U.S. found that the sky got quite clear without planes flying. He checked the measurements and found that the misty layer the plans produce block some of the incoming sunlight in the day time. The misty layer blocks some of the outgoing heat in the night time from escaping into space.
    The explanation was that with the layer the daytime temperature is a bit cooler and the night time temperature is a bit warmer. Without the layer the daytime temperature is a bit warmer and the night time temperature is a bit cooler.
    To be honest, even as a child I realized that a cloud free sky makes the daytime warmer and the night time cooler. If you have clouds in the sky the sun is blocked and it doesn’t get too warm and in the night time the clouds will keep it a bit warmer.
    Why do people draw the curtains or close the shutters in the day and open the windows in the night?

  4. “As is our stated blog policy, no discussions or linkages to discussion of chemtrails will be permitted. Grousing about it won’t change anything.”
    An attempt to keep the comments stream slender and sylphlike ?
    On a serious note 1944 was a curious year for weather. There were summer storms which delayed “Overlord” and destroyed the US “mulberry” installation. And an early and harsh winter which contributed to a severe famine in the Netherlands. Is there any recognition of this by the papers authors?
    REPLY: From experience I have leaned the topic always degrades into a pointless shouting match, requiring huge amounts of time to moderate. I simply don’t have the time nor the will to waste my time (or the time of other moderators) on trying. There are plenty of other places to discuss this issue.
    BTW, lest someone accuse me of being draconian, take a moment to read the comments policy over at Greg Laden’s science blog.
    http://scienceblogs.com/gregladen/about.php (see Nefarious Commenting Policy midway down)
    That’s a real eye opener. – Anthony

  5. However, the contrails from these aircraft significantly suppressed the morning temperature increase across those areas which were heavily over flown.
    Not a very scientific study as again there is no knowing what the temperature would have been if the aircraft had not flown. Furthermore, for contrails to form, the air at the aircraft levels has to be supersaturated with water vapor which everyone knows is many times more effective at absorbing infrared than CO2. However, it is interesting that the statement above is diametrically opposed to the NASA Langley ‘research’ that showed that temperatures were cooler when aircraft were not flying and contrailing due to the post 9/11 flying ban,
    Nevertheless, as any holidaymaker will tell you if there is a layer of cirrus the beach is not as hot.

  6. What an interesting take on climate.
    We live near an airport from which both jet and turbo prop aircraft fly. It is very noticeable that turbo prop contrails are a fraction of those caised by jet aircaft, which of course didn’t mostly come into operation during the time scale mentioned. That might affect calculations.
    However, much more interestng is that GS Callendar-yes that one- made a considerable contribution to the war effort by creating the means to keep fog laden British airfields clear. He did this-ironically- by burning millions of gallons of oil which drove the fog away. It would be interesting to know if this had any effect.
    tonyb

  7. In chasing up information on the WW2 contrails, I found that the bomber pilots were aware that the Luftwaffe fighter pilots use contrails to track and attack incoming bombing missions.
    On record are some that flew at different altitudes to avoid the conditions that made them vulnerable to this type of attack.
    I won’t mention I was using it to debunk —–

  8. Somehow, I just knew “East Anglia” would worm its way into this somewhere! It’s interesting but I don’t buy it just for now 🙂
    Alas, no mention of the tragic & horrific loss of life in that hectic period from all the lead poisoning in the high-level & low-level atmosphere. You know, the .303, .30, the 50 calibre, the 20mm, 30mm, & 40mm cannon, & fire from the ground type of lead poisoning, the sort that has a somewhat instantaneous hazzard for human health. It all must have fallen to the ground at some stage! What about all the sulphur from the cordite? Did that not also have an effect on atmospherics close to the ground & in the air? What about all that pollution from sinking oil tankers burning away for hours on end at times, & in storage facilities on land in Western Europe, Eastern Europe, Asia & the Phillipines, etc. What about adding in Pearl Harbour, based next to an active volcano, (although any natural pollution was outshone by that from humans on that momentously tragic day) now quaintly referred to as “environmental terrorism”. How much do volcanoes put up in the atmosphere in the way of particulates, sulphur & Co2 in comparison? Iceland, Chile, Indonesia, to mention three of late! Just a thought.

  9. Perhaps the days on which bombing raids were executed were not selected independently of the weather.

  10. The team found that on the morning of the 11th 1444 aircraft took off from airfields across south east England into a clear sky with few clouds. However, the contrails from these aircraft significantly suppressed the morning temperature increase across those areas which were heavily over flown.
    So the clear first experimental signal about aircraft contrails is that they suppress (i.e. make lower) temperatures. As one would expect from clouds – increasing reflection of sunlight.
    Also as one would expect, the exact opposite of the AGW orthodoxy that aircraft promote climate warming.
    Why do clouds look grey from underneath and white from above? Because they reflect more radiation from above than from below.
    Or try this one: what radiates more energy, the sun or the earth (as measured in the troposphere-stratosphere)? (Clue: its the sun.)
    Once again the attack against civil aviation from the CAGW movement, on supposedly environmental grounds, is shown to be nothing more than the pursuit of a class war, anarchist-anti-capitalist agenda and totally dislocated from any scientific reality.

  11. Strikes me as a bit odd that piston engined B17s, with an operating height of something like 10,000 feet loaded, could be even vaguely comparable to today’s jets…

  12. Last spring, air travel over Western Europe was shut down for 2-3 weeks. That should be an opportunity for someone interested in pursuing this line.

  13. “They selected raids that involved over 1000 aircraft and that were followed by raid-free days with similar weather which might be used for comparison. The resulting top 20 raids revealed 11th May 1944 as the best case study.”
    The others didn’t show the desired results??? Two years of data and they come up with one day???
    Clever idea for the study. I’d like to see more detail.

  14. A bit of searching for International Journal of Climatology found this link for those who may want to read more in detail.
    http://onlinelibrary.wiley.com/doi/10.1002/joc.2392/full
    World War II contrails: a case study of aviation-induced cloudiness
    A. C. Ryan
    A. R. MacKenzie
    S. Watkins
    R. Timmis
    Article first published online: 8 JUL 2011
    DOI: 10.1002/joc.2392
    Copyright © 2011 Royal Meteorological Society

  15. I think perhaps the effeect of the bombs they dropped would have had more effect on climate than the contrails … just musing.
    Hey, contrails lead to cooling! Let’s all fly around the world to save the planet 🙂 Maybe Greenpeace can sponsor my next trip to Australia.

  16. Just a couple of small points. Most of these contrails occurred over the European mainland and not over England as often the planes were still climbing or descending at the end of the raid and so less likely to generate contrails. Also the planes would be taking off from diverse locations and meeting up at altitude over the sea to the east of England resulting in contrails being more widely dispersed than this summary seems to suggest.

  17. Further thought, tactically the “Thousand bomber raids ” would not have all taken off at the same time or flown the same route but would have been dispersed to a variety of different flight plans to force defending fighters to cover as much sky as possible and stop the enemy from concentrating their forces with much greater effect.
    The “thousand bomber raids” were only intended to put a thousand bombers in waves over the target, not fly them as a single body to it. From that I would have expected any contrails to be equally dispersed and should then question the effects observed.

  18. Wasn’t there an extensive study done when concorde operation was first being studied?

  19. 1444 aircraft is a LOT of aircraft. Look at the photo with the contrails from 10 aircraft in formation. How this applies today is problematic. Aircraft typically do not fly in formation and are typically separated by 5 miles horizontally. They also tend to follow the same routes so the contrails while spread out do not cover the sky.

  20. @Sam Hall, “I thought only jet engines produced contrails.”
    Even a glider will produce a contrail in the right conditions.

  21. In WW2 there were 1000 bomber raids by the RAF, but they operated at night. The USAF operated by day. Formations would have been assembled from several airfields and would not necessarily have combined fully before they left the English coast. To get a better fix, a researcher should also explore the availability of data in countries that were overflown, when the formations are more likely to have joined up, eg in France, Belgium, the Netherlands and Germany.
    I lived in the south of England in WW2 and well remember large aircraft formations of bombers at high altitude, as well very spectacular low altitude formations of fighters and fighter bombers – Mustangs and Thunderbolts often c100 at a time.

  22. mct – The B-17F and B17G models had a service ceiling of 37,500 ft but the normal tactical altitude was in the 21,000 to 27,000 ft altitude range with a nominal bomb load of 4000 lb. The tactical operating speed was between 180 and 215 mph. The B-17 was one of two four engine bomber the US us in the ETO; the other being the B-24. The main models used were the B-24D and B-24J. The B-24 service ceiling was 28,000 ft with the tactical operating altitude between 18,000 and 22,000 ft with a nominal 5000 lb bomb load. The tactical operating speed was 205 mph.
    Planners always attempted to avoid altitudes where contrails would develop as they were an arrow pointing to the formations for the German fighters but were not always successful. Note in one of the pictures above that the high formation was producing contrails and the lower one was not. Planners also attempted to route the formations around German flak installations although they couldn’t avoid the flak concentrations around the targets. Bombing altitudes were always a compromise between the lowest to get decent bombing accuarcy and high enough to avoid as much of the flak as possible. However, very few heavy bomber missions flew with bombing altitudes below 18,000 to 20,000 feet although the Ploesti, Romania refinery minimum altitude raid in August 1943 does come to mind. That mission saw horrendous losses to the bomber force.
    Don Bennett
    Evanston, WY

  23. Neil Jones says:
    July 8, 2011 at 5:28 am
    Further thought, tactically the “Thousand bomber raids ” would not have all taken off at the same time or flown the same route but would have been dispersed to a variety of different flight plans to force defending fighters to cover as much sky as possible and stop the enemy from concentrating their forces with much greater effect.
    The “thousand bomber raids” were only intended to put a thousand bombers in waves over the target, not fly them as a single body to it. From that I would have expected any contrails to be equally dispersed and should then question the effects observed.

    The bomber stream flew in large formations along the same route. Not the exact same routes, but close.

  24. From the full report comes this quote:
    Our aim was to show that historical data, such as WW2 bombing raids, may be an extremely important tool in closing the gap between the overwhelmingly large number of theoretical-based modelling studies that have been published in recent years (Marquart et al., 2003; Minnis et al., 2004; Dietmueller et al., 2008; Lee et al., 2009) and the limited number of observation-based studies (Travis et al., 2002, 2004).
    Bravo to the scientists for going where few climate scientists have gone before. Using real world data instead of computer model generated fantasy data to form their conclusions.

  25. Surely a fully laden B17 or B24 leaving Eastern England would take some considerable distance to attain the altitude at which a contrail would result. Therefore it would seem unlikely to affect the weather in the UK more likely the western side of mainland Europe. Anyway it looks like another reason to obtain research funds using climate change as the raison d’être.

  26. “The team found that on the morning of the 11th 1444 aircraft took off from airfields across south east England into a clear sky with few clouds. However, the contrails from these aircraft significantly suppressed the morning temperature increase across those areas which were heavily over flown.”
    Okay, this is interesting. All the bomber bases were on the eastern side of the UK.
    As an old fisherman fishing the rivers of the UK for many years I can state for sure that the predominant winds/weather comes from the west. At what height do the piston engine bombers have to attain before they make contrails?
    The bombers had to take off and start to climb to height followed by other squadrons meeting up over the North Sea as they headed for Germany. Are we really expected to think that they circled over the eastern UK, burning up precious fuel whilst they reached the height required.
    Add that to the fact that the bombers were petrol driven, piston engines how do you equate that to sublimation from a jet engine? Given that Europe was occupied how can they ensure weather information was accurate. Would you nip out to check a thermometer with 1444 bomber flying overhead? Just makes me wonder!

  27. tonyb says:
    July 8, 2011 at 1:44 am
    “We live near an airport from which both jet and turbo prop aircraft fly.”
    Check out what drives the propeller on a Turbo Prop engine Tony.

  28. Since it takes time and distance for the bombers to climb to altitude and since the prevailing winds at altitude would have moved the vapor trails away from England, it seems to me that most of the vapor trails would have been east of England.

  29. Alan the Brit says:
    July 8, 2011 at 2:07 am
    Somehow, I just knew “East Anglia” would worm its way into this somewhere! It’s interesting but I don’t buy it just for now 🙂
    [snip]…What about all the sulphur from the cordite?…[snip]

    Cordite does not contain sulphur.
    http://en.wikipedia.org/wiki/Cordite

  30. Brian Hull says:
    July 8, 2011 at 7:12 am
    Surely a fully laden B17 or B24 leaving Eastern England would take some considerable distance to attain the altitude at which a contrail would result. Therefore it would seem unlikely to affect the weather in the UK more likely the western side of mainland Europe. Anyway it looks like another reason to obtain research funds using climate change as the raison d’être.

    You are on the money here, I think. The contrails would have more likely formed over Germany and German occupied territories than over England.

  31. Don Bennett says:
    July 8, 2011 at 6:43 am

    Thanx for pointing out the false claim that these missions were flown at only 10,000 feet.

    peter_ga says:
    July 8, 2011 at 2:11 am
    Perhaps the days on which bombing raids were executed were not selected independently of the weather.

    I wondered the same thing, if these researchers took that into account as well as hundreds of other factors the mission planners did.
    And has been pointed out earlier, the highest concentration of these contrails would have been at or near the target, not over England.

  32. oldtimer says:
    July 8, 2011 at 6:13 am
    In WW2 there were 1000 bomber raids by the RAF, but they operated at night. The USAF operated by day. …[snip]

    And they were low level raids, as they didn’t have the bomb sight systems that allowed the US to conduct high altitude “precision” bombing. It is very possible the RAF never reached the altitude where contrails might form.

  33. It has been suggested (with very simple supporting math) that a 1-2% decrease in cloudiness would account for the post 1975 heating of the planet. Since we are looking at only a few tenth’s of a degree planetary average (through perhaps 3X that over a large landmass), a “small” signal that shows up from the 9/11 event and (now) this WWII data could be very significant.
    A small or weak signal of cooling is what a warmist would say invalidates a cloud-solar heating; a small or weak signal of temperature rising is what a warmist would say is proof of an anthropogenically induced, global heating catastrophe.
    Cognitive dissonance rules; cognitive consistency drools.

  34. I found more details here:
    http://www.foxnews.com/scitech/2011/07/08/did-colossal-wwii-bombing-raids-alter-weather/
    Here’s an excerpt:

    MacKenzie, Roger Timmis, and Annette Ryan at Lancaster, working with the Royal Air Force Museum at Hendon, went back through the records from 1943 to the war’s end in 1945. With the help of the museum staff, they were able to center on the May 11 raid. From pilot briefings, they found the planes in the morning mission produced contrails when they reached 12,000-15,000 feet, relatively low, so they concentrated on that mission. There were no missions the next few days and the weather did not change notably, providing something of a control.
    The morning squadron was enormous, 363 B-24s and 536 fighters in escort. The target was marshalling yards in France, places where the Germans assembled troops. All or most of the planes produced contrails.
    Using data from weather stations on the ground, they looked at the increase of temperature through the morning from stations covered by the contrail cloud and found the temperature increase during the morning lagged by about 2 degrees Fahrenheit from stations not under the cloud. The contrails, being white, were reflecting sunlight back into space.

  35. Ah, the old contrail trick.
    Isn’t it a wee bit ironic to study contrails and their impact on weather or climate amidst the hurling into the local atmosphere of millions of tons of dirt, soil, gas, chemicals, soot, and all other kinds of particular particulates from thousands of tons of exploding and burning materials?

  36. Not very meaningful, considering the WW2 era planes did not reach the altitudes of modern day commercial aircraft. That makes for considerably different atmospheric conditions. Another point would be the exhaust temperatures compared to jet engine exhaust and particle size and density, both which would not be comparable, either.

  37. Another study which is more then likely trying to find the proverbial needle in the haystack. Sure, its possible contrails have an effect on weather patterns, but the effect is probably too minor to really be noticed, and trying to find it 60+ years ago is just laughable…
    Kind of reminds me of the effect increased CO2 has on the temperatures of our planet. Too minor to find, but that does not stop people from claiming they did find that needle!

  38. TonyB:
    “We live near an airport from which both jet and turbo prop aircraft fly. It is very noticeable that turbo prop contrails are a fraction of those caised by jet aircaft, which of course didn’t mostly come into operation during the time scale mentioned. That might affect calculations.”
    +++++++++
    The important consideration is the condensation of water produced by combustion. The fuels have hydrogen in them (hydro-carbon fuels with CxHy compositions). The difference between the fuels is probably not as important as the altitude because of the temperature difference with altitude.
    Jet A is just kerosene (paraffin) with some antifreeze in it, and covers the range of C9H20 to C20H42 (though it varies, I agree). Gasoline is not so different in chemical composition as to overwhelm the influence of altitude/temperature so the fuel is not really a big player in the result.
    An additional consideration is that water vapour (not condensed droplets) absorbs IR radiation very effectively. In other words, do not be distracted by the white contrails – the whole profile of H2O vapour and droplets (white clouds) is involved in interfering with the temperature below.

  39. This seems like an awful lot of meticulous research to prove that clouds (contrails) cause shade, which temporarily lowers temperatures in the shaded areas. Am I missing something?
    More interesting would be to assess whether or not the entire 6 years of war lowered global temperatures as a result of the particulates and firestorms created.

  40. Nuke says:
    July 8, 2011 at 8:44 am
    I found more details here:
    http://www.foxnews.com/scitech/2011/07/08/did-colossal-wwii-bombing-raids-alter-weather/
    Here’s an excerpt:
    MacKenzie, Roger Timmis, and Annette Ryan at Lancaster, working with the Royal Air Force Museum at Hendon, went back through the records from 1943 to the war’s end in 1945. With the help of the museum staff, they were able to center on the May 11 raid. From pilot briefings, they found the planes in the morning mission produced contrails when they reached 12,000-15,000 feet, relatively low, so they concentrated on that mission. There were no missions the next few days and the weather did not change notably, providing something of a control.

    Trust Fox News to get it wrong.
    Table III in the paper shows that of all the raids they considered for possible study, the one they selected was the only one that had no adjacent raid-free days. So there was no ‘providing something of a control’.

  41. Clay Marley says:
    July 8, 2011 at 10:08 am
    More interesting would be to assess whether or not the entire 6 years of war lowered global temperatures as a result of the particulates and firestorms created.
    http://data.giss.nasa.gov/gistemp/graphs/
    According to GISS, global land-ocean mean temperature peaked in 1942 and didn’t reach the same mean temperature again until 1979.
    Was the cooling between the 1942 and 1979 a result of WWII? You tell me.

  42. So if this caused cooling in they daytime, what about the night time bomber raids by the RAF, did they elevate night time temperatures, along with all the smoke reaching high levels from intense incendiarly bombing?

  43. In which case, we should be promoting aviation, instead of taxing it. Looks like politicians got it wrong again.
    .

  44. >>PeteH
    >>Are we really expected to think that they circled over the eastern UK, burning
    >>up precious fuel whilst they reached the height required.
    Actually they did. It was rather dangerous to climb and form formations further eastwards, as you may well get shot down. Formation flying in the daytime was the key to US operations over Germany. The British flew at night instead, in much looser formations of aircraft.
    >>Add that to the fact that the bombers were petrol driven, piston engines
    >>how do you equate that to sublimation from a jet engine?
    Very similar. The only difference is that early piston engine aircraft often could not climb high enough to get into the contrailing layer. But clearly sometimes they did, especially later in the war with more powerful engines and better airframes.
    .

  45. “significantly suppressed the morning temperature increase” thus “it is indeed possible to see the effects of AIC in surface weather observations, but that the signal is weak.”
    I think the supposed weakness is a cover-up of the up cover.

  46. >>Tonyb
    >>It is very noticeable that turbo prop contrails are a fraction of
    >>those caused by jet aircaft,
    Because they often do not fly high enough. Their engines are not so height-critical, relative to fuel burn, and their flights are shorter.
    .
    >>MCT
    >>Strikes me as a bit odd that piston engined B17s, with an operating
    >>height of something like 10,000 feet loaded, could be even vaguely
    >>comparable to today’s jets…
    The later B-17s had a max altitude of about 30,000 feet. Clue – that is why the crew used oxygen, and the waist gunners had electric suits. The British Lancasters had much better load performance, but flew lower and at night, so would not have been included in this study.
    .
    >>Neil
    >>Further thought, tactically the “Thousand bomber raids ” would not
    >>have all taken off at the same time
    Actually, the idea was to swamp the German defences, and so the formations were grouped together quite tightly in time and space. Some units had to wait quite some time for the formations to gather, and could indeed get low on fuel.
    .
    >>DAV
    >>Aircraft today typically do not fly in formation and are typically
    >>separated by 5 miles horizontally. They also tend to follow the
    >>same routes so the contrails while spread out do not cover the sky.
    Not so. Modern commercial aircraft fly on controlled airways, but the wind aloft pushes the contrails downwind. A quartering crosswind aloft can often produce a dense mesh of contrails across the whole sky, blocking out the Sun, which is often mis-interpreted by the ignorant as being ******* trails.
    .
    >>Nuke
    >>You are on the money here, I think. The contrails would have
    >>more likely formed over Germany and German occupied territories
    >>than over England.
    Not so. Not only did the bombers form their formations over East Anglia – but this was a fine high pressure day, which are normally associated with easterly winds in the UK. Only at the really higher levels are the jet-streams more likely to be westerly.
    .
    >>Kaboom
    >>Not very meaningful, considering the WW2 era planes did not reach
    >>the altitudes of modern day commercial aircraft.
    Most US bombers in 1945 could reach 30,000 ft. I think they went for high altitude for added safety, rather than the UKs Lancaster bombers that went lower level with larger payloads at night.
    In comparison, there are many older coal-burning B737s still flying that cannot manage more than 32,000 ft, when fully laden.
    .

  47. “Civil aviation was rare in the 1940s, so USAAF combat missions provide a strong contrast between areas with busy skies and areas with little or no flight activity.”
    There were few areas with little or no activity. There were airfields all over the place and often very close to each other. The amount of runway would have peaked in 1945 and has declined ever since, and continues to decline.
    On one particular day in WWII there were over 25,000 allied airmen in the air at once. The largest raid had over 5000 planes in it and was a continuous stream of planes from the UK to two seperate targets. Although there are differences between a piston engine and a jet engine, a contrail is a contrail, whether generated aerodynamically or by hot exhaust. There has not been such a high concentration of aircraft over Europe since.
    The current world fleet of airliners is around 20,000. The number of road vehicles globally is around 800,000,000. There is somewhere around 1000 airliners on the UK register, while there are around 30,000,000 UK road vehicles. And yet it seems all the attention is on aviation. Over time we have moved more people with fewer planes, and yet the only numbers that are discussed are the amount of people travelling by air which increases at a faster rate than the increase in flights.

  48. Good to know the people killed on that day by the raids in Belgium, Luxemburg and a number of places in Germany served a good cause after all /sarc off
    Anyway – somewhat flimsy data to base any kind of conclusion on.

  49. So, essentially, if some 1400 and some more aircraft are said to have had a minute impact on the weather Gods of the 1940’s, . . .
    In 2010 London Heathrow Airport shuffled almost 66 million people through its gates, coming and going. That’s about 181 000 per day, and if each aircraft is carrying 200 passengers thats some 900 flying apparatuses. Add Gatwick’s stats, which is a bout half, thus make up for 1400 and some aircraft in a day for only two airports in jolly England.
    In 2010 there was about three million people flying though the hundred most frequent airports per day. That’s about 15,000 aircrafts that can take 200 passengers.
    According to ACI Europe, who represent some 400 commercial airports in europe, they have 1.5 billion passenger throughput per year.
    That’s a lot of contrails.
    If we add cargo flights . . . it will just make those 1400 something look even more silly, however if those pesky 1400 and some had a minute effect, what effect does today’s tens of thousands of high flying aircraft have?

  50. @Billy Liar:
    While the link provided was at fownewd.com, the article clearly says the content was written by the Inside Science News Service.
    Trust the foxnews bashers to get it wrong, perhaps?

  51. “The team found that on the morning of the 11th (May) 1444 aircraft took off from airfields across south east England”.
    The report doesn’t specify the type of aircraft, nor does it specify exactly when they took off, or at what time intervals.
    US 8th AAF B17s and B24s were all based north of London. There were none in the south east of England.
    http://www.303rdbg.com/h-england-map.html
    Aircraft taking off during daylight on the 11th May 1944, from the south east of England, are most likely to have been twin engine tactical bombers and single engine fighter bombers, heading for France, to bomb railways, bridges and German defences prior to Operation Overlord, the invasion of France on the 6th June. These attacks would have been carried out at comparatively low levels.
    In May 1944, the US 8th AAF was under the command of SHEAF, and was largley involved tactical bombing in in preparation for Overlord. These attacks would have been carried out at lower levels, due to the nature of the targets, and the fact that the Allies had established air superiority over France at this stage of the war.
    Large scale strategic, high-level bombing did not resume until September 1944.
    I think Profs Mackenzie and Timmis are way off target (excuse the pun).

  52. @Ralph
    I really wish I had the patent on the pulverizer for those coal-burning B737’s you were talking about.

  53. @Rainer S
    The good cause was that they weren’t able to make any more stuff to kill good guys.

  54. I don’t know where I saw it, but there is a site that has daily images of all the contrails in the US. They cover the US in the daytime in much the same fashion as a view of all the lighting of the US at night.
    That’s a lot of artificial albedo during the day and radiation emitting at night. Perhaps this is something to factor into the UHI budget.

  55. “AshCloud says:
    July 8, 2011 at 5:56 pm
    “The team found that on the morning of the 11th (May) 1444 aircraft took off from airfields across south east England”.
    The report doesn’t specify the type of aircraft, nor does it specify exactly when they took off, or at what time intervals.
    US 8th AAF B17s and B24s were all based north of London. There were none in the south east of England.
    http://www.303rdbg.com/h-england-map.html
    Aircraft taking off during daylight on the 11th May 1944, from the south east of England, are most likely to have been twin engine tactical bombers and single engine fighter bombers, heading for France, to bomb railways, bridges and German defences prior to Operation Overlord, the invasion of France on the 6th June. These attacks would have been carried out at comparatively low levels.”
    973 B17 and B24 heavy bombers of the 8th Air Force took off on May 11 from bases in East Anglia (which is in southeasten England) to attack four marshalling yards in northern France as part of the preparation for Overlord. The did not operate at low altitude (which was near suicidal for heavy bombers in daylight). Most of the 471 remaining missions would have been fighter escorts. As a matter of fact those 1444 missions probably apply only to the 8th AF. It seems to be too low a figure to include 9th AF tactical missions and RAF and FAA operations.

  56. I’ve asked this question here once before on a similar thread and not got a satisfactory answer, I’ll try again. If con triails and cirrus can reflect shortwave radiation (sunlight) what do they do to longwave IR (heat), do they act like an aluminum blanket? I know water vapour absobs IR and re-emits in all directions, but do water droplets and ice particles act like difuse reflectors for IR radiation.

  57. @ mct
    “…B17s, with an operating height of something like 10,000 feet loaded…”
    I think you’ll find the standard mission cruising altitude for B17’s to be around 30,000 ft.

  58. Brilliant! The main factor in deciding whether large bombing raids go ahead is the weather (at the departure airfields, assembly points and at the target), and some genius seeks to find a correlation between the weather and the bombers? You’ve GOT to be kidding!
    The main determinant of whether an aircraft contrails or not is the meterological conditions you’re flying though. I’ve often observed in Europe that an aircraft produces ‘patches’ of contrails as it flies through what must be interleaving airmasses. I’m not sure it’s significant but the light where I live in Western Australia has a real hard-edged clarity which is very different to the diffuse light you tend to get in Europe and there’s not much high-altitude aviation over our skies…
    Sort of related, the UK Met Research Flight (which did a lot of atmospheric science on “Snoopy” before NERC took it over) originated during WW2 to study contrail formation (a dead giveaway if you’re trying to sneak in unobserved). Many Battle of Britain photos of the sky show spiraling contrails from the dogfights, including the iconic picture of St. Pauls (google “St Paul’s Battle of Britain Contrails”). I reckon back in those days you could probably rely on the weather records too – I recall my ex-RAF father telling me that the RAF used to have station meteorologists who could forecast almost to the minute when fog would appear, and not a computer model in sight. Of course, that’s why so many long term weather records come from airports too, and I’d take the data before automation any day (I loved the comment someone posted here in a different thread about digitising an optical reading of a conventional thermometer – you should commercialise that!).
    As to whether clouds make it hotter or colder – of course it depends where the sun is! If it’s shining through the cloud you cut the incident radiation which leads to less energy below the cloud. Otherwise they’re going to trap heat in. I very definitely believe in a greenhouse effect when we’re talking about clouds and water vapour. But is that weather or climate? it’s certainly not equilibrium 🙂

  59. 1DandyTroll says:
    July 8, 2011 at 4:12 pm
    “If we add cargo flights . . . it will just make those 1400 something look even more silly, however if those pesky 1400 and some had a minute effect, what effect does today’s tens of thousands of high flying aircraft have?”
    I think you will find there are only two tens of thousands at the most. Also a lot of freight is sent on regular passenger services.

  60. Dixon says:
    July 9, 2011 at 7:34 am
    “As to whether clouds make it hotter or colder – of course it depends where the sun is! If it’s shining through the cloud you cut the incident radiation which leads to less energy below the cloud. Otherwise they’re going to trap heat in. I very definitely believe in a greenhouse effect when we’re talking about clouds and water vapour. But is that weather or climate? it’s certainly not equilibrium :)”
    Surely once the heat source (sun) is blocked/reflected then the only heat that can be trapped is residual which is less than that before being blocked. In other words cooling is retarded. I have experienced first hand high thin cloud cover cutting off my lift on a cross country glider flight. it was immediate and to put it another way, the clouds did not increase the lift / thermals, they switched them off, immediately.

  61. >>Ascloud
    >>US 8th AAF B17s and B24s were all based north of London.
    >>There were none in the south east of England.
    East Anglia is classed as the South East. It is certainly not the midlands, or the North East, and the Middle East is something completely different…!!
    These were B-17s and B-24s taking off from the hundreds of airfields in the English Fens (East Anglia).
    .
    >>mike g says. July 8, 2011 at 6:17 pm
    >>I really wish I had the patent on the pulverizer for those coal-burning
    >>B737′s you were talking about.
    Oh, I’m not sure you would. If you could see the smoke coming out of the back, it is clear that the pulveriser does not work too well. Just as well there are only a few coal-burners still operating in Africa and other locations of dubious aeronautical expertise.
    .
    >>dlb
    >>II know water vapour absobs IR and re-emits in all directions, but do
    >>water droplets and ice particles act like difuse reflectors for IR radiation.
    Good question. I have not seen an experiment for this. As an observation of weather (being a weather observer), any cloud cover will stop surface temperatures falling so fast, be that water droplet cover or ice crystal cover. But this is a subjective opinion, not fact.
    .
    >>Stephen Skinner says: July 9, 2011 at 11:16 am
    >> Also a lot of freight is sent on regular passenger services.
    Not that much – passengers take to much of their own nowadays, and freighters need a dedicated hub system to sort out the freight and connect with the road system. In Europe there are now about 300 freight aircraft flying every night for the likes of TNT, DHL and Fed Ex.
    .

  62. I see a lot of speculation on this thread, when there are other sources available for some of the missing information. As always, popular articles on science often get things incorrect, but some key details are given.
    http://www.tgdaily.com/sustainability-features/57098-wwii-bombing-raids-affected-british-weather
    http://www.foxnews.com/scitech/2011/07/08/did-colossal-wwii-bombing-raids-alter-weather/
    http://www.newscientist.com/article/dn20667-second-world-war-bombers-changed-the-weather.html
    http://www.sciencedaily.com/releases/2011/07/110708084008.htm
    Also, some resources on the missions on 11 May 1943. These may be harder to verify, but seem to be essentially in agreement
    http://www.scottylive.com/mac_calendar/1944/May%2044%20Daily/May_11_1944.htm
    THURSDAY, 11 MAY 1944
    EUROPEAN THEATER OF OPERATIONS (ETO)
    STRATEGIC OPERATIONS (Eighth Air Force): Mission 350: 364 B-24s and 536
    fighters are dispatched to bomb marshalling yards in France; 8 B-24s and 5
    fighters are lost:
    1. 144 are dispatched to hit Mulhouse; 94 bomb the primary, 19 hit Belfort,
    13 bomb Orleans/Bricy Airfield and 2 hit Mezidon/Pithiviers; 1 B-24 is lost,
    2 damaged beyond repair and 17 damaged; 1 airman is KIA, 7 WIA and 40 MIA.
    2. 74 are dispatched to Belfort; 33 bomb the primary and 24 hit Chaumont;
    1 B-24 is lost.
    3. 76 are dispatched to Epinal; 68 hit the primary and 1 bombs Caen
    Airfield; 3 B-24s are lost.
    4. 70 are dispatched to Chaumont but none bomb; 3 B-24s are lost, 1
    damaged beyond repair and 30 damaged; 1 airman is WIA and 31 MIA.
    Escort is provided by 147 P-38s, 188 P-47s and 201 P-51s; the P-38s claim
    2-0-0 Luftwaffe aircraft on the ground, the P-47s claim 3-0-2 in the air
    and 2-0-6 on the ground and the P-51s claim 3-0-0 on the ground; 2 P-4s and
    3 P-51s are lost, 1 P-51 is damaged beyond repair and 2 P-38s, 6 P-47s and
    2 P-51s are damaged; 5 pilots are MIA.
    Mission 351: In the afternoon, 609 B-17s and 471 fighters are dispatched
    to hit marshalling yards in Belgium, France, Germany and Luxembourg; 8 B-17s
    and 4 fighters are lost; primary targets are Brussels/Midi (55 bomb),
    Brussels (49 bomb) and Liege, Belgium (119 bomb, 2 lost); Saarbrucken (58
    bomb, 5 lost), Kons Karthaus (55 bomb) and Ehrang (60 bomb, 1 lost), Germany;
    and Luxembourg (53 bomb); 12 hit the secondary target at Thionville, France;
    and 16 hit Volkingen, Germany; 19 hit Bettembourg, Luxembourg and 51 hit
    other targets of opportunity; 8 B-17s are lost, 1 damaged beyond repair and
    172 damaged; 2 airmen are KIA, 23 WIA and 83 MIA. Escort is provided by 99
    P-38s, 182 Eighth and Ninth Air Force P-47s and 190 Eighth and Ninth Air
    Force P-51s; the P-51s claim 11-0-4 Luftwaffe aircraft; 4 P-51s are lost,
    the pilots are MIA.
    Mission 352: 4 of 5 B-17s drop 2.4 million leaflets over Denmark; 2
    airmen are KIA and 3 WIA.
    4 B-24s are dispatched on CARPETBAGGER missions.
    850th Bombardment Squadron (Heavy), VIII Air Force Composite Command
    attached to 801st Bombardment Group (Provisional), moves from Eye to
    Cheddington, England with B-24s; the squadron is flying CARPETBAGGER
    missions.
    TACTICAL OPERATIONS (Ninth Air Force): 330+ B-26s attack airfields at
    Beaumont-le-Roger and Cormeilles-en-Vexin and marshalling yard at Mezieres/
    Charleville, France and Aerschot, Belgium. Bad visibility and failure to
    rendezvous with fighters cause 100+ aborts. This is start of Ninth Air
    Force’s participation in AAF pre-invasion offensive against airfields.
    14th Liaison Squadron, XIX Tactical Air Command attached to Third Army,
    moves from Alderley Edge to Knutsford, England with L-5s; first mission is
    in Jul 44.
    http://www.8thafhs.org/combat1944a.htm
    THURSDAY, 11 MAY 1944
    STRATEGIC OPERATIONS (Eighth Air Force): Mission 350: 364 B-24s and 536 fighters are dispatched to bomb marshalling yards in France; 8 B-24s and 5 fighters are lost:
    1. 144 are dispatched to hit Mulhouse; 94 bomb the primary, 19 hit Belfort, 13 bomb Orleans/Bricy Airfield and 2 hit Mezidon/Pithiviers; 1 B-24 is lost, 2 damaged beyond repair and 17 damaged; 1 airman is KIA, 7 WIA and 40 MIA.
    2. 74 are dispatched to Belfort; 33 bomb the primary and 24 hit Chaumont; 1 B-24 is lost.
    3. 76 are dispatched to Epinal; 68 hit the primary and 1 bombs Caen Airfield; 3 B-24s are lost.
    4. 70 are dispatched to Chaumont but none bomb; 3 B-24s are lost, 1 damaged beyond repair and 30 damaged; 1 airman is WIA and 31 MIA.
    Escort is provided by 147 P-38s, 188 P-47s and 201 P-51s; the P-38s claim 2-0-0 Luftwaffe aircraft on the ground, the P-47s claim 3-0-2 in the air and 2-0-6 on the ground and the P-51s claim 3-0-0 on the ground; 2 P-4s and 3 P-51s are lost, 1 P-51 is damaged beyond repair and 2 P-38s, 6 P-47s and 2 P-51s are damaged; 5 pilots are MIA.
    Mission 351: In the afternoon, 609 B-17s and 471 fighters are dispatched to hit marshalling yards in Belgium, France, Germany and Luxembourg; 8 B-17s and 4 fighters are lost; primary targets are Brussels/Midi (55 bomb), Brussels (49 bomb) and Liege, Belgium (119 bomb, 2 lost); Saarbrucken (58 bomb, 5 lost), Kons Karthaus (55 bomb) and Ehrang (60 bomb, 1 lost), Germany; and Luxembourg (53 bomb); 12 hit the secondary target at Thionville, France; and 16 hit Volkingen, Germany; 19 hit Bettembourg, Luxembourg and 51 hit other targets of opportunity; 8 B-17s are lost, 1 damaged beyond repair and 172 damaged; 2 airmen are KIA, 23 WIA and 83 MIA. Escort is provided by 99 P-38s, 182 Eighth and Ninth Air Force P-47s and 190 Eighth and Ninth Air Force P-51s; the P-51s claim 11-0-4 Luftwaffe aircraft; 4 P-51s are lost, the pilots are MIA.
    Mission 352: 4 of 5 B-17s drop 2.4 million leaflets over Denmark; 2 airmen are KIA and 3 WIA.
    4 B-24s are dispatched on CARPETBAGGER missions.
    850th Bombardment Squadron (Heavy), VIII Air Force Composite Command attached to 801st Bombardment Group (Provisional), moves from Eye to Cheddington, England with B-24s; the squadron is flying CARPETBAGGER missions.

  63. Ralph and tty …..
    East Anglia in the south east ??? Eh ?
    Unless East Anglia has moved due to global warrming, East Anglia is in the east of England.
    The east of England is ….. “Directly to the north of London, the region is based around the ancient kingdom of East Anglia – covering the counties of Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Norfolk and Suffolk”.
    http://www.visiteastofengland.com/
    http://en.wikipedia.org/wiki/East_Anglia

  64. Ralph says:
    July 9, 2011 at 11:42 am
    >>Stephen Skinner says: July 9, 2011 at 11:16 am
    >> Also a lot of freight is sent on regular passenger services.
    >”Not that much – passengers take to much of their own nowadays, and freighters need a >dedicated hub system to sort out the freight and connect with the road system. In Europe there >are now about 300 freight aircraft flying every night for the likes of TNT, DHL and Fed Ex.”
    I was interested in what the actual numbers were as there are figures for aircraft movement, passenger numbers and freight. ACI give figures for all but not a break down of aircraft movements by passenger and freight. I found a break down on individual airport and government web sites and it indicates that the majority of freight is moved on regular passenger flights. I also found the following which might be of interest.
    http://www.fta.co.uk/export/sites/fta/_galleries/downloads/air_freight/the-role-of-air-freight-in-the-UK.pdf
    “Air transport is not used for most freight. Indeed, the volumes are actually very small. Air freight – accounts for only 0.5 per cent of the UK’s international goods movements by weight – sea freight (95 per cent) and the Channel Tunnel (4.5 per cent) account for the rest.
    However, the importance of air freight is shown by the fact that when freight is measured by value, 25 per cent of the UK’s international goods movements are made by air. For products such as manufacturing exports beyond the EU, this raises to 55 per cent. It is valuable or perishable commodities that have to be moved by air.
    How does air freight operate?
    Around 60 per cent of air freight travels in the hold of passenger planes, so it travels at the same time as passenger flights do. The remainder is carried on specialist freight services, which includes express carriers.”
    What frustrates me is the selection of data that is designed to suite a partisan position. What is interesting about the figures above is the % of UK air freight moved by weight. You can be sure that opposition to air freight will use the % by value as it looks bigger. This is the same for the opposition to passenger flying where the % increase in passenger numbers will be quoted rather than the % increase in flights. The 1st flight out of Heathrow had 1 passenger and 1 pilot.

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