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Could Aviation be part of the climate change solution?

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Could Aviation be part of the climate change solution?

Old 11th Oct 2019, 20:41
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Could Aviation be part of the climate change solution?

Hi Folks,

i cant help wonder if Aviation could be part of the climate change solution as opposed to the perceived problem.

Would it be practically possible fo fuel jet engines on aircraft with hydrogen so that the water exhaust actually formed high level clouds which in turn would possibly provide an element of shade to the earth below and maybe slow down global warming?

I appreciate that there are a lot of gaps in the thought process there but still canít help but think that this could definitely maybe possibly be a better Aviation emissions solution than electric aircraft.

Yours hopefully,

StraighrLevel
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Old 11th Oct 2019, 20:58
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Dunno,
Iím too busy making sure the chemtrails are deploying properly
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Old 11th Oct 2019, 20:59
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No.
Water vapour is itself a potent greenhouse gas.

https://www.ncdc.noaa.gov/monitoring...-gases.php#h2o
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Old 11th Oct 2019, 21:17
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To amplify from (google "increasing cloud cover in upper athmosphere effect on global warming" and look for the "Clouds and Global Warming - NASA Earth Observatory" entry, sorry cannot post links).

If more high clouds were to form, more heat energy radiating from the surface and lower atmosphere toward space would be trapped in the atmosphere, and Earthís average surface temperature would climb.
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Old 11th Oct 2019, 21:26
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As the climate has changed radically over the millennia, has aviation ever been a factor.
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Old 11th Oct 2019, 21:34
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Using hydrogen instead of hydrocarbons would certainly eliminate the CO2 production but burning the fuel mostly used today, JET A-1, already produces about 1.4 tonnes of water vapour per tonne of fuel burned. Atmospheric O2 contributes the additional mass. The process also creates over 3 tonnes of CO2. Variations in existing atmospheric water vapour content determine whether contrails form and indeed whether they persist. Interestingly if the right conditions exist for contrails to persist, vast amounts of additional atmospheric water vapour will condense and freeze on the ice crystals that make up contrails. Some measurements have determined that 1 tonne of burnt jet fuel can lead to 200 tonnes of contrail forming.
I'm still researching this next statement but...my understanding of contrail formation is that the formation process is dependent on the presence of particles of soot in the exhaust plume that act as condensation nuclei. No hydrocarbons, no soot, no contrail.
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Old 11th Oct 2019, 22:15
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Originally Posted by Meester proach View Post
Dunno,
Iím too busy making sure the chemtrails are deploying properly
Braco Sir, Bravo!!
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Old 11th Oct 2019, 22:36
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Originally Posted by Busbuoy View Post
Using hydrogen instead of hydrocarbons would certainly eliminate the CO2 production but burning the fuel mostly used today, JET A-1, already produces about 1.4 tonnes of water vapour per tonne of fuel burned. Atmospheric O2 contributes the additional mass. The process also creates over 3 tonnes of CO2. Variations in existing atmospheric water vapour content determine whether contrails form and indeed whether they persist. Interestingly if the right conditions exist for contrails to persist, vast amounts of additional atmospheric water vapour will condense and freeze on the ice crystals that make up contrails. Some measurements have determined that 1 tonne of burnt jet fuel can lead to 200 tonnes of contrail forming.
I'm still researching this next statement but...my understanding of contrail formation is that the formation process is dependent on the presence of particles of soot in the exhaust plume that act as condensation nuclei. No hydrocarbons, no soot, no contrail.
my understanding of contrail formation is that the formation process is dependent on the presence of particles of soot in the exhaust plume that act as condensation nuclei. No hydrocarbons, no soot, no contrail.
Nope - they ( engines ) may help or hinder certain contrails , but contrails form from other areas of the airplane- dependent on local conditions. Wingtips re a prime area along with some protrubances which change ' local ' air pressure ( slipstream) . They can be ' stopped' by certain chemicals introduced in the slipstream or also by changing altitude and speed.
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Old 11th Oct 2019, 23:32
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The data is very limited and largely circumstantial, however there is some evidence that - in the immediate aftermath of 9/11 - the grounding of virtually all commercial air traffic over the continental US resulted in slightly lower temperatures. Some researchers suspect the reduction in water vapor being injected into the upper atmosphere by all those grounded aircraft was responsible.
That the average ground temperatures dropped slightly is pretty much certain, cause and effect is rather more questionable (particularly with a single data point).

Besides, "practical" and H2 powered aircraft don't belong in the same sentence given current technology. There is simply no practical way to contain the volume of hydrogen necessary for long range flight - the density of even liquid H2 is far less than Jet A - and keeping a large volume of cryogenic fuel on a commercial aircraft wouldn't leave much room for passengers and cargo (you're not going to be putting it in the wing).
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Old 12th Oct 2019, 03:13
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Some decades ago I read an article that seemed technically respectable (can't remember where, possibly Scientific American) which said that liquid hydrogen fueled aircraft would start to become economical around 1.4 million pounds. There was a tradeoff between fuel weight savings and fuel tank weight and bulk/drag (cylinder on top of fuselage). Lower fuel consumption per unit of payload might compensate for the greater greenhouse effect of water vapour and clouds (I'm not up to the data and math). However if the A380 is too big then immediate prospects for hydrogen fueled aircraft don't look good. In any case it would only be feasible for very high-traffic routes.
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Old 12th Oct 2019, 03:21
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Grebe:
The type of condensation you describe is not generally called a contrail in my experience. When it formed in the reduced pressure areas around the lifting surfaces of a manouevring fighter we used to call it "ecto"-plasm but that was just a colloquillalism.
In any case my research leads me to believe that the ice crystal contrails to which the OP refers require a condensation nucleus to form.
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Old 12th Oct 2019, 04:30
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Originally Posted by Busbuoy View Post
Grebe:
The type of condensation you describe is not generally called a contrail in my experience. When it formed in the reduced pressure areas around the lifting surfaces of a manouevring fighter we used to call it "ecto"-plasm but that was just a colloquillalism.
In any case my research leads me to believe that the ice crystal contrails to which the OP refers require a condensation nucleus to form.
Sort of splitting hairs- suggest you do a bit of research on contrail issues and stealth bombers eg B2- some claims/articles are phony, and some are ' probably' correct, and whether from wings and major pressure- temp changes at low alt re fighter or at high alt, the physical requirements are essentially the same- rapidly expanding air causes a temp drop- and the local humidity does the rest. IF one can make the necessary measurements in the right areas, then one knows at what altitudes and speeds contrails can be expected or practically nil.
granted, most " contrails " are from engines ( jet or prop ) and the easiest way to avoid is to change altitude and speed. Airliners dont care, but military does. And then if one wants to get real picky, other than the ' straight line ' - how does one determine the real diff between clouds a˜d contrails say with a physical measurement of a cloud and ditto for a contrail ? The net effect is the same.

And then there is your breath in cold weather or walk in freezer or on a cold mountaintop ..
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Old 12th Oct 2019, 05:02
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At the risk of this becoming a thread-distracting pi55ing match, more research has confirmed that "exhaust" contrails are the predominant (I would like to say "only" but I honestly haven't read every peer-reviewed scholarly article on the subject) type of ice crystal based contrail and as such are the only persistent form of contrail. I have learned that the other type (for me "ecto") is an "aerodynamic" contrail and requires that the atmosphere be above freezing and reasonably close to saturation. As no energy is removed from the air parcel on aircraft passage the temperature will rise again above the saturation point and the localised condensation will evaporate hence be non-persistent.
I can say with relative certainty that I never saw an "aerodynamic" contrail form above the freezing level but I sure as hell formed a few "exhaust" ones when I didn't pay proper attention to the met man's morning brief.
But hey, contrails can be useful.
A 4 ship of Eaglejets in wide combat4 coming beak to beak at 50,000ft M1.5 and conning, accompanied by Eagle lead's gravelly voice on the back radio saying "Gentlemen, the Claw!!!" focusses your survival instincts sharpish!!!
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Old 12th Oct 2019, 08:26
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For the energy density problem already mentioned, consider that greater fuel volume = more drag = less efficiency. There is also accident safety to consider. But most pertinently in climate change terms there is the question of how the hydrogen is generated in the first place. It does not occur naturally in significant quantity and has to be produced. Whatever process is adopted, it will be less than 100% efficient so additional energy is needed from the first stage. Burning fossil fuels to generate electricity to do this, typically at lower efficiency than a jet engine can achieve, is clearly a nonsense unless all pollutants can be captured, in which case why the current angst? Nuclear fission might be credible in capacity terms but has cost and political issues; good luck getting the green lobby on board. And renewables need to get closer to existing electrical power demand before it becomes conceivable to add another huge requirement. The received wisdom in futurist writing used to be that nuclear fusion power would be the step which unlocked a Ďhydrogen economyí but that seems as far away as ever...

Last edited by Easy Street; 12th Oct 2019 at 11:11.
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Old 12th Oct 2019, 12:28
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As anyone who lives in northern latitudes can attest, it is significantly colder on clear days/nights, than cloudy.

Unfortunately, I spent quite a bit of time in Norfolk, VA, which has a lot of air traffic over it. It was easy to see how all of the "chemtrails" come together on many, many days and by early afternoon, it was all hazed over...I was not enthused about this observation.





Stuff like this is common
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Old 12th Oct 2019, 17:24
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Water vapour is not just a greenhouse gas, it is responsible for a considerably larger proportion of the greenhouse effect than all other greenhouse gasses on Earth combined! The funny this is everyone gets so exited about greenhouse gasses, and the greenhouse effect, yet we would not even be here in the first place without them!
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Old 12th Oct 2019, 19:38
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Problem is too many people in the greenhouse

(and yes, Africa & India, I'm looking at you)

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Old 12th Oct 2019, 20:21
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Originally Posted by tdracer View Post
The data is very limited and largely circumstantial, however there is some evidence that - in the immediate aftermath of 9/11 - the grounding of virtually all commercial air traffic over the continental US resulted in slightly lower temperatures. Some researchers suspect the reduction in water vapor being injected into the upper atmosphere by all those grounded aircraft was responsible.
That the average ground temperatures dropped slightly is pretty much certain, cause and effect is rather more questionable (particularly with a single data point).

Besides, "practical" and H2 powered aircraft don't belong in the same sentence given current technology. There is simply no practical way to contain the volume of hydrogen necessary for long range flight - the density of even liquid H2 is far less than Jet A - and keeping a large volume of cryogenic fuel on a commercial aircraft wouldn't leave much room for passengers and cargo (you're not going to be putting it in the wing).

Only quoting your post tdracer as you were the only one to reference 9/11.

I always wondered about those temperature claims made over the years about the days immediately following 9/11.

This report is well worth the read. Itís just 4 pages long yet accurately describes their reference points around the US, the average Diurnal Temperature Range over the period Ď71 to Ď01, the actual change in airmass over the NE US that week, etc.

Basically, the witnessed change in temperature wouldíve happened anyway.

Do read it. Very interesting.


https://www.int-res.com/articles/cr2...6/c026p001.pdf
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Old 13th Oct 2019, 01:38
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Originally Posted by Mac the Knife View Post
Problem is too many people in the greenhouse
Yes.

Originally Posted by Mac the Knife View Post
(and yes, Africa & India, I'm looking at you)
So sod off all you third world people; there isn't enough room in the greenhouse for you to burn coal, drive cars, and fly places, we got here first?

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Old 13th Oct 2019, 05:00
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Water vapour as a greenhouse gas

Originally Posted by GS-Alpha View Post
Water vapour is not just a greenhouse gas, it is responsible for a considerably larger proportion of the greenhouse effect than all other greenhouse gasses on Earth combined! The funny this is everyone gets so exited about greenhouse gasses, and the greenhouse effect, yet we would not even be here in the first place without them!
Yes, water vapour is the most powerful greenhouse gas in one sense. John Tyndall discovered the basics in the 1850s. The Wikipedia article "greenhouse gas" says that water supplies 36-72% of the warming effect, varying with location. CO2 is number 2. However. the average water molecule stays in the atmosphere for 9 days, while the residence time for CO2 molecules is thought to vary from 30 to 95 years. Evaporation of water varies with temperature. Therefor we call CO2 the "driver." Water vapour content of the atmosphere follows the CO2 content.

Regarding "we wouldn't be here without them"; yes, Joseph Fourier brought to notice in 1824 the fact that the Earth is considerably warmer than the physics of his time could explain, and proposed as one possible explanation that some property of the atmosphere caused it to retain heat. "The dose makes the poison." Recently the Earth's temperature has been like Goldilocks' third bowl of porridge, just right. We don't want it hotter, especially as the Sun's radiation has slowly increased over its lifetime, and the disposition of the continents right now is helpful for cooling.
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