Saturday, October 12, 2019

Northwest Contrails and Global Warming

The new GOES-17 weather satellite, with its higher resolution imagery, does an excellent job in showing the contrails that often form over our skies.

For example, the visible image at 7:51 AM this morning shows contrails (the white lines) near the Oregon/Washington border (see below)


And there were plenty over Oregon and northern California at the same time.


As described in previous blogs, contrails form as combustion from burning jet fuel injects moisture and small particles into the cold, upper atmosphere, producing a line of ice crystals behind the plane.


What is less well known is the significant net low-level warming effect of such contrails.

Why did I say, net warming effect?  Because contrails both warm and cool, with the warming dominating.

Let me explain.    On one hand, the ice crystals in contrails cool the lower atmosphere, since they reflect some of the sun's radiation in the visible part of the spectrum back into space.  But the ice clouds associated with contrails also influence radiation in the infrared (long wave) part of the spectrum.   Such clouds can absorb infrared radiation coming up from below and can emit infrared radiation back down to the surface.  This acts to warm the lower atmosphere in a similar way that greenhouse gases such as carbon dioxide and water vapor do.  Think of a big blanket aloft.


It turns out that the warming effects are larger than the cooling effects:  thus, contrails have a net warming effect.

The IPCC (Intergovernmental Panel on Climate Change), encompassing scientists from all over the world, have analyzed the contrail warming and has found it significant, but smaller than the overall  impacts of increasing CO2.  In 2005, it was estimated that aircraft provided about 5% of the global warming forcing, with the contrail effect being the largest component--greater than the warming from the CO2 released by burning jet fuel.  And aircraft mileage is increasing rapidly.

The jet contrail warming will be a very difficult contribution to lessen, since only fossil fuels can provide the energy densities needed for commercial aircraft.  Fortunately, it only represents a small proportion of the problem.


22 comments:

  1. Rich people fly. Hence the reason why I keep voting no on carbon tax aimed at the working poor and working lower middle class.

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    1. for better or worse, almost everyone flies these days.

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  2. That's good thinking. I'll bet every one of the tens of thousands of commercial flights every day have at least one "rich person" on board.

    No new taxes because rich people fly on airplanes! It just makes sense..

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  3. Maybe net warming but in areas where the contrails become concentrated in winter months they can flat ruin a sunny warmish winter day, I was vacationing in Palm springs one winter when the contrails blotted out the sun several days and the cooling effect was stunning along with being very annoying.

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  4. Back during the FAA's shutdown of all air traffic during the 911 crisis, there was a 'window' of opportunity to see what the contrails did: https://globalnews.ca/news/2934513/empty-skies-after-911-set-the-stage-for-an-unlikely-climate-change-experiment/

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  5. This comment has been removed by the author.

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  6. This is interesting as the growth of air travel is going to grow by leaps and bounds in places like Asia and Africa over the next decade. I have flown domestically in the Philippines and the flights are dirt cheap. Almost anyone can afford and as a result the growth in domestic air travel there is astonishing. Conversely their will also be a rise in clean aircraft and electric aircraft motors but realistically this is still far off before it becomes common for commercial airliners.

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  7. not at all defending what organic farmers is driving at but rest assured, in a global context which global warming risk is, only rich people fly

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  8. I get the feeling the commenter above has no idea how the rest of the country actually lives. Try doing a job requiring you to spend half of your life flying in coach and staying in roadside motels, all because you have a family to support. Not very "rich," you might say.

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  9. Interesting airplane example. A Qantas 747-400 with RR RB211s. 30 year old version of a 50 year old airplane design with 50 year old engines. Still even with 4 thirsty holes gulping jet fuel back then, there was far less overall air travel, so net that old humpback whale Boeing pollutes far less. Engines today are far more efficient, but there are exponentially more of them in service. Inefficient VOR based navigation is going away too, in favor of GPS, but again there are so many more planes flying. Pilots don't have to stick to set highways in the sky, instead they can follow the best winds and use the satellites to stay on course. That should at least spread the contrails out a bit!

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  10. Surprised you didn't mention the paper referenced here: ( http://www.atmos.washington.edu/~rennert/etc/courses/pcc587/ref/Travis-etal2002_Nature.pdf) about the effects observed on diurnal temperatures over the US after flights were banned following 9/11...

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  11. but wait, I thought contrails were actually dropping mind control chemicals on the population below...

    Geez! I need to read better interwebs...

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  12. At one time air travel was largely reserved for the affluent, just as automobiles once were, but those days are long gone. People around the world have become remarkably prosperous.

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  13. So, what you are saying is that contrails do the same thing as a natural cloud does, only less because it takes up less space in the atmosphere. WOW, what a revelation. Glad
    we studied that.

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    1. Hi - you are correct. But, importantly, the point here is that man (by creating air travel) has added to the net warming that Cliff has explained clearly. Without the jets and air travel, there would be no contrail clouds that are net-contributing to the surface warming. Randall Benson, PhD Atmospheric Science

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  14. Rich people fly...? perhaps in the ‘60s, but that is clearly an out of touch answer. Planes are glorified buses these days and will continue to be based on my experience. Plus some people, like my wife, simply have to fly for work and not pleasure because sometimes meetings have to be face to face and not “teleconferenced.” smh

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  15. Wasn't it George Carlin who claimed that God created humans because he/she wanted plastic and did not know how to create that?

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  16. Interesting, Cliff. I didn't know the contrails' role in warming and appreciate the education.

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  17. Cliff, pure hydrogen has a higher energy density, at least on a weight basis, than fossil fuels, which is why space rockets use it, and hydrogen has been considered as a fuel for commercial aviation, but liquid hydrogen has to be used. So it will be expensive. There will still be the ice crystals, of course.

    Jimmy, I think that contrails only spread out when the surrounding atmosphere is already supersaturated. So if it is any comfort, when jet trails spread and blot out the sun, it would probably have happened soon anyway (as cirrostratus clouds) even without the jets.

    The use of electric planes is the only solution I can think of at the moment.

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  18. One question though, if a cloudy day has a net 24 hour average temperature that is cooler than that of a sunny day, which I think is true, why doesn't that work for contrails?

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    1. Because it does not fit the IPCC narrative.

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  19. "Electric aircraft motors," said the Seattle "progressive" who doesn't know a single thing but will deliver a lecture anyway. LOL.

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