From Wiley-Blackwell via Eurekalert
Wartime weather records reveal impact of contrails caused by USAAF raids
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
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.”
As is our stated blog policy, no discussions or linkages to discussion of chemtrails will be permitted. Grousing about it won’t change anything.
Well, I learned something new. I thought only jet engines produced contrails.
@Sam Hall, “I thought only jet engines produced contrails.”
Even a glider will produce a contrail in the right conditions.
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.
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
The bomber stream flew in large formations along the same route. Not the exact same routes, but close.
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.
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.
“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!
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.
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.
Cordite does not contain sulphur.
http://en.wikipedia.org/wiki/Cordite
You are on the money here, I think. The contrails would have more likely formed over Germany and German occupied territories than over England.
Thanx for pointing out the false claim that these missions were flown at only 10,000 feet.
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.
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.
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.
I found more details here:
http://www.foxnews.com/scitech/2011/07/08/did-colossal-wwii-bombing-raids-alter-weather/
Here’s an excerpt:
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?
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.
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!
I wonder what those poor souls receving the bombs would think about this codswallop!
PeteH
There is no comparison between their size and the amount of contrails the respective planes leave.
tonyb
@mct: Read all about it: http://www.aviation-history.com/boeing/b17.html
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.
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.
One more impossible “science”. There is no precision to achieve a conclusion like that.