Aircraft contrails contributing to global warming?

The prevailing thought amongst the majority of the population is that carbon dioxide (CO2) produced from the burning of fossil fuels is the lead factor in global warming. While I am not doubting that CO2 is a greenhouse gas, I am somewhat unconvinced that it is as major a contributor to the effect as the press would have me believe.



Water, water, everywhere...

I find it peculiar that water vapour, a more potent greenhouse gas, is not receiving as much coverage in the press. According to the National Oceanic and Atmospheric Administration (NOAA), water vapour is the most abundant greenhouse gas on the planet.


Greenhouse Gases - Frequently Asked Questions

As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the relative humidity can be higher (in essence, the air is able to 'hold' more water when its warmer), leading to more water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapor and so on and so on. This is referred to as a 'positive feedback loop'. However, huge scientific uncertainty exists in defining the extent and importance of this feedback loop. As water vapor increases in the atmosphere, more of it will eventually also condense into clouds, which are more able to reflect incoming solar radiation (thus allowing less energy to reach the Earth's surface and heat it up).

Here is another article detailing the effects of water vapour in the atmosphere, but unfortunately it has too many terms I am not familiar with. Perhaps someone else can explain it to me, and to the rest of ATS.

The climatic effects of water vapour

With that out of the way, let me continue by addressing the topic title.



Jet-setting our way to warmer climes

It cannot be denied that air travel by members of the public has increased over the past few decades. The advent of budget airlines has increased this phenomena in order of magnitudes. But how is all this air travel affecting our planet? The most popular theories out there would argue that more carbon dioxide is injected directly into the atmosphere with so many planes up in the sky. Water vapour is again conveniently ignored.

Dr Nicola Stuber published a study in the journal Nature a theory proposing that water vapour from aircraft contrails can have a big impact on global warming. As reported in National Geographic News:


Source: Airplane Contrails Boost Global Warming, Study Suggests

According to Stuber, the effect is most pronounced at night. While contrails block out sunlight during the day, it prevents heat from radiating off into space at night. You could probably confirm this by observing the difference in the ambient temperature between cloudy and cloudless nights. To combat this, Stuber proposes a reduction in the number of night time flights.



High-altitude atmospheric roasting planes

Another research on the other hand suggests that the warming effect from air travel is produced by contrails that form at high altitudes. The researchers assert that contrails that form high in the sky form condensations that allow the heat from the sun to shine in but not radiate out.

High-altitude cirrus clouds, both natural and jet-induced, are unlike thicker low-altitude clouds, which block sunlight from reaching the surface. The thinner cirrus, which float in the sky at 20,000 feet or higher, act like a see-through blanket - letting sunlight pass in, while trapping reflected heat.

Source: Longer Airline Flights Proposed to Combat Global Warming


Their proposed solution? Fly at lower altitudes. That may be easier said than done, however. Flying at lower heights consumes more fuel and time, which could ultimately defeat the whole purpose of this exercise. Still, the scientists argue that the effect would be less damaging to the environment.



Conclusion: contrails confound climatologist

There is still much we need to know about how water vapour affects the climate. It doesn't help that water vapour can create a feedback loop of heating which creates more water vapour. In the final analysis, the jury is still out whether contrail formation effects global warming as significantly as proposed by some studies. I myself am inclined to believe that it does. Cloud-cover and ambient temperature is something you can observe by yourself, without the need for complex instruments. But perhaps a study conducted after the 9/11 attacks proved it best:

“September 11 – 14, 2001 had the biggest diurnal temperature range of any three-day period in the past 30 years,” said Andrew M. Carleton[1]. Not in three decades had there been such a large temperature spread between the daytime highs and the nighttime lows.

Source: Contrails: What’s Left Behind Is Bad News



Other Resources:
The importance of the diurnal and annual cycle of air traffic for contrail radiative forcing
Water builds the heat in Europe
Global Warming Supercharged by Water Vapor?

Good idea to get all this in one place

You should also look at:

Minnis etal 2003 - Cirrus trends, contrails and climate

It is concluded that the U.S. cirrus trends are most likely due to air traffic. The cirrus increase is a factor of 1.8 greater than that expected from current estimates of linear contrail coverage suggesting that a spreading factor of the same magnitude can be used to estimate the maximum effect of the contrails. From the U.S. results and using mean contrail optical depths of 0.15 and 0.25, the maximum contrail–cirrus global radiative forcing is estimated to be 0.006–0.025 W m22 depending on the radiative forcing model. Using results from a general circulation model simulation of contrails, the cirrus trends over the United States are estimated to cause a ropospheric warming of 0.28–0.38C decade21, a range that includes the observed tropospheric temperature trend of 0.278C decade21 between 1975 and 1994.

Also:

Imperial College, London - Climate Change and the future of air travel

DERA (UK MoD) Contrail Uncertainties

IPCC 4AR Chapter 2 Section 2.6 - Contrails and Aircraft-induced Cloudiness (page 186 onwards)

(Note the IPCC downplays Minnis' findings - although the issues raised by Hansen have, I believe, been addressed by Minnis. I post this link to show the current 'official' stance by the main proponents of GHG emission induced AGW)

reply to post by Essan


Hey, thanks for the links! That's a lot to read. I haven't gone through the PDFs yet, but I did read the press release. I like this part of the release the best:

Dr Noland also believes that the work has direct relevance to aircraft manufacturers. He says, There is little more that aircraft designers can do to increase engine fuel efficiency at high altitude, but designing new aircraft that can be as fuel efficient flying at 20,000 feet, as todays aircraft are at 35,000 feet, would help eliminate contrails.

That's an angle I didn't consider. It's an opportunity to make money, not by me personally, but still. Where there's an opportunity for cash, they'll be those who'll work on it, for sure

great post. great thread. great info.

From what i read, it makes a lot of sense. Of all the data possessed by you two, would there be information anywhere comparing the amount of flights in the skies above certain countries and the relative diurnal temperature range over a specific period of time?

Just thinking about developing countries or other countries who have had a significant boost in air traffic and then seeing if the diurnal temperatue range changed as air traffic increased. This could go a long way to helping provide more data similar to that September 11 data - which is very compelling.

They're certainly linked to the matter of global dimming. There was a program on this recently on Discovery (I think) and it actually has the effect of masking the impact of human-created global warming.


[edit on 25-9-2007 by Byrd]

Is this chemtrail disinfo?

When I drove to an appointment this morning in my car, I helped
maintain the global warming trend. If global warming is being
caused by man, as some scientists maintain, shouldn't all consumers
of products and services take the blame? Our cumulative effect
has to dwarf the warming effect caused by Contrails from jets..no?
-cwm

Originally posted by merkaba93
Is this chemtrail disinfo?

Yes. It's being going on since 1970

ams.allenpress.com...

Although the daft Chemtrails conspiracists are inadvertently involved in spreading disinfo about the real concerns over air travel and contrails

reply to post by Byrd


From what I've read it seems the cooling effect of global dimming (via cloud cover) only happens during the day. At night cloud-cover actually acts like a blanket, keeping the atmosphere underneath warm by preventing heat from radiating off into space. An example would be the temperature difference between night and day in a desert.

reply to post by merkaba93


What if chemtrails are the disinfo?

And no, this thread isn't really about those things. It's a thread to bring forth awareness about how the extra cloud-cover up above due to contrails might have an effect on the ambient temperature closer to ground level.

reply to post by carewemust


I'm kind of still in the middle of the issue, man made or not, I'm not sure. But this (as in extra cloud cover at night), I'm quite certain. And since there is something we can do about it, then I'd like to go with that. Basically my whole thoughts on the global warming issue can be summed up in my signature.

Anyway, about the pollution from aviation:



*Source - Scroll down and look for the article titled "Aviation industry in eye of climate-change storm"

The rest of the article is quite interesting.

I was under the impression that the contrails actually masked the effects of global warming as well. I believe that there was a document out there that showed the global temperature spiked a couple degrees higher the days after 9/11 when no one was allowed to fly in the US. Whomever did the study blamed the spike directly on the lack of air travel.

Hey, Beachcoma:

Interesting. For fun, if you can find the data, it would be interesting to see what sort of temperature reaction was to be found over the US after 9/11 when the planes were all grounded.

You should be able to compare to other countries to see if it's local to the US or worldwide.

In Huntsville, we saw a definite drop in nighttime temps, it was very dramatic. I recall coming to the same conclusion - maybe the contrails are having a real effect.

reply to post by Karlhungis


Sure, it spiked during the day, but at night all the heat radiates back out into space because nothing was trapping it. Try observing it yourself, all it takes is a thermometer. You'll actually see a difference between cloudless and overcast nights.


reply to post by Tom Bedlam


Trying to find data outside of the US has proven more difficult than I had anticipated; there's a lot of stuff out there that's unrelated and I'm not sure what keywords to pick any more (plus my eyes are getting heavy).

However, I did find the full, original study, which was published partially in the journal Nature, which was quoted in the article I linked. So here's the link to the unadulterated study. No more telephone-relay games:

Regional Variations in US Diurnal Temperature Range for the 11–14 September 2001 Aircraft Groundings: Evidence of Jet Contrail Influence on Climate

I'll try looking again after I've had enough rest

The thing about clouds is they do two things. They provide warming and cooling. They will trap whatever warmth you had built up and keep overnight low temperatures from falling. But they will also put a cap on daytime heating as well. I believe short term clouds will cause a small amount of warming but long term they will cause cooling as they block sunlight from reaching the surface. The good thing about clouds of any type is they don't stick around long and the problems they create often correct themselves very fast.

What you say is true, but when it comes to the clouds laid down by airliners, it's not necessarily the case. Unlike your regular cumulus clouds, these are thin, wispy cirrus clouds -- they let some light in but they prevent heat from radiating out. Unlike regular clouds that just dissipate (or precipitate), they can be renewed whenever another aeroplane plies through the airway. And there are a lot of those in the sky, with the number steadily growing (although industry analysts suggest that the growth will plateau this year).

Exactly. Every single contrail is a cloud that would not have otherwise have existed. Every single contrail adds a tiny bit to climate (and weather) change. Ultimately, everyone who flies is just a tiny bit responsible.

But for some it's easier to blame secret govt experiments than accept responsibility for their own actions. Hence the chemtrail myth.

No-one is suggesting we stop flying, but it is time we woke up to the consequences.

Hi

Just listened to your last Sunday's broadcast and heard at the end that you're talking about planes' vapour (or con) trails as cloud formers.

Some time ago, I heard on one of the World Service's broadcasts that, thanks to the 9/11 attacks (when they grounded all flights) people were able to work out that con trails during daylight hours were actually an assistance to prohibiting global warming whereas con trails during the hours of darkness were an aggrovator of same.

I hope you are going to be able to confirm, or otherwise, what I've previously heard.

Many thanks.
Global Warming Survival Center

[edit on 29-6-2010 by Hollioake]

Personally I find the whole hypothesis that climate change is linked to CO2 emissions rather hysterical and in conflict with much of the scientific evidence....

That much being said I accept that there is a huge chunk of the population that believe it with religious fervor.

During WW2 the Germans developed an atomic powered aircraft which was capable of flight at Mach 1.6 up to altitudes of 58,000 ft. The thrust was equivalent to a 30,000lb jet engine. It appears to have worked by the emission of accelerated ionised hydrogen or ammonia.

The radiation from this is stopped by 60 kilometres of atmosphere and is highly directional thus will not cause radiation under the flight path, only directly behind the emitter aircraft. It will not penetrate the fuselages of other aircraft passing behind either. It does not result in any contamination by radionuclides. The ionised matter ejected at high altitudes will serve to restore the earth's Ozone layer.

Using this concept it is perfectly feasible to reduce worldwide commercial airliner emissions by half simply by augumenting existing jets with an atomic power plant.

There is no need to fear the technology because the fear is based on a misunderstanding of how it works. It is not the same as a nuclear power plant. It does not require Uranium, Plutonium or any of the other nasties.

I would appreciate some feedback on such a proposal...

One thing is for sure. You can't decapitate aviation without offering an alternate in it's place.

Originally posted by sy.gunson
Personally I find the whole hypothesis that climate change is linked to CO2 emissions rather hysterical and in conflict with much of the scientific evidence....

That much being said I accept that there is a huge chunk of the population that believe it with religious fervor.

Nice one !! , best thing I have read on ATS this week,

snoopyuk

Cool story Bro!

BUT

Global Warming ended 16 years ago.