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Eliminating contrails from flying could be cheap

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Re: Eliminating contrails from flying could be cheap

#21

Post by burkaman »

imgabe wrote: post #16

If the incoming radiation can pass through, why can't it pass through on the way out?

Greenhouse gases only interact with specific wavelengths of light. A lot of sunlight comes in as visible or ultraviolet light, mostly passing through those gases. It hits the surface of the Earth and is absorbed and then re-emitted as infrared light, and a lot of that is just the right wavelength for greenhouse gases to interfere. Here's a good article about the physics of this: https://www.quantamagazine.org/the-quantum-mechanics-of-gree...

Re: Eliminating contrails from flying could be cheap

#22

Post by dylan604 »

readthenotes1 wrote: post #13
dylan604 wrote: post #4

"Why aren’t we doing more to eliminate contrails?" I'm just having a hard time groking that contrails are really that impacting. TFA just quotes a bunch of numbers, but does not actually discuss how the numbers were derived. Maybe I've just been around too many people into Chemtrails, but this just reads to me as an offshoot of that type of thinking.

There's some anecdata from 9/11 https://globalnews.ca/news/2934513/empty-skies-after-911-set...

The NASA image does make contrails look much larger than say from the ground, but even in the same image true cloud cover is clearly more complete than all of the contrails combined from the same image

Re: Eliminating contrails from flying could be cheap

#23

Post by justonceokay »

imgabe wrote: post #16

If the incoming radiation can pass through, why can't it pass through on the way out?

Single particles of radiation coming from the sun have higher energy than single particles radiating from the earth. Even though the total energy entering and leaving earth is at a near equilibrium.

My mental model is that a bullet leaving the barrel of a gun has much more penetrative power than that same bullet once it has ricocheted off a concrete wall.

Re: Eliminating contrails from flying could be cheap

#24

Post by burkaman »

grues-dinner wrote: post #18
burkaman wrote: post #11

Earlier quoted context omitted.

It links to this post which has a little more technical explanation: https://notebook.contrails.org/comparing-contrails-and-co2/ And also this paper which is a very in-depth technical explanation: https://www.sciencedirect.com/science/article/pii/S135223102... I understand why you're reminded of chemtrails, but it is not crazy or conspiratorial to look at these giant lines in the sky and think "those things must be d…

> not crazy or conspiratorial to look at these giant lines in the sky and think "those things must be doing something" I think more accurately it's not crazy to think they might be doing something. I could equally be convinced if researchers crunched the numbers and concluded they might seem big but they're negligible on a global scale. In fact the same figure of "only 3%" of flights really have an effect" could easi…

Sure, I meant "must be" in the colloquial sense of "I have a suspicion", not "I am absolutely certain". Like "it's 5pm, must be a lot of traffic on the highway right now". If traffic turned out to be light I would be mildly surprised, update my assumptions and move on with my life.

Re: Eliminating contrails from flying could be cheap

#26

Post by continuational »

imgabe wrote: post #16

If the incoming radiation can pass through, why can't it pass through on the way out?

Basic greenhouse effect: Visible light (and ultraviolet light) comes in relatively unhindered. Gets absorbed by the earth and heats it up. The heat is emitted as infrared radiation. This gets absorbed by CO2 (and equivalents) and reemitted in a random direction. Takes a long time to reach space by chance, so the energy stays in the atmosphere for a while.

Re: Eliminating contrails from flying could be cheap

#27

Post by DemocracyFTW2 »

dylan604 wrote: post #4

"Why aren’t we doing more to eliminate contrails?" I'm just having a hard time groking that contrails are really that impacting. TFA just quotes a bunch of numbers, but does not actually discuss how the numbers were derived. Maybe I've just been around too many people into Chemtrails, but this just reads to me as an offshoot of that type of thinking.

Wikipedia[1] states it very clearly:

> It is considered that the largest contribution of aviation to climate change comes from contrails. In general, aircraft contrails trap outgoing longwave radiation emitted by the Earth and atmosphere more than they reflect incoming solar radiation, resulting in a net increase in radiative forcing. In 1992, this warming effect was estimated between 3.5 mW/m2 and 17 mW/m2. In 2009, its 2005 value was estimated at 12 mW/m2, based on the reanalysis data, climate models, and radiative transfer codes; with an uncertainty range of 5 to 26 mW/m2, and with a low level of scientific understanding. [...] Contrail cirrus may be air traffic's largest radiative forcing component, larger than all CO2 accumulated from aviation, and could triple from a 2006 baseline to 160–180 mW/m2 by 2050 without intervention.

What I can say is that even in a place with moderate air traffic, you get to see lots of contrails crisscrossing the sky on some days; in places near busy airports I hear that a sizable fraction of all cloud cover is due to lingering contrails.

[1] https://en.wikipedia.org/wiki/Contrail#Impacts_on_climate

Re: Eliminating contrails from flying could be cheap

#28

Post by mulmen »

SoftTalker wrote: post #17
steanne wrote: post #6

Earlier quoted context omitted.

> The proposed detours typically result in a 1% shift (and again, this is only for a small percentage of flights). That means increasing fuel use and flight time by around 1%. So if your flight is three hours long, it’s only adding an extra two minutes. For a 10-hour flight, six minutes. This seems socially acceptable to me; most people would barely notice.

Airlines will certainly notice a 1% fuel cost increase however. But, they'll just add it to ticket prices.

It’s not a 1% increase in fuel costs. It’s 1% of 3% (for 80% mitigation) to 17% (for total mitigation). That’s a 0.03% to 0.17% increase in fuel costs.

Re: Eliminating contrails from flying could be cheap

#29

Post by roadside_picnic »

dylan604 wrote: post #4

"Why aren’t we doing more to eliminate contrails?" I'm just having a hard time groking that contrails are really that impacting. TFA just quotes a bunch of numbers, but does not actually discuss how the numbers were derived. Maybe I've just been around too many people into Chemtrails, but this just reads to me as an offshoot of that type of thinking.

Contrails observably suppress the Diurnal Temperature Range (i.e. they make it cooler during the day).

How could this be observed you might ask? It turns out there was a study done immediately after the grounding of airplanes during the September 11th, 2001 events to take advantage of this unique incidence of effectively halting all air transportation for a few days [0]

0. https://journals.ametsoc.org/view/journals/clim/17/5/1520-04...

Re: Eliminating contrails from flying could be cheap

#30

Post by jvanderbot »

dylan604 wrote: post #4

"Why aren’t we doing more to eliminate contrails?" I'm just having a hard time groking that contrails are really that impacting. TFA just quotes a bunch of numbers, but does not actually discuss how the numbers were derived. Maybe I've just been around too many people into Chemtrails, but this just reads to me as an offshoot of that type of thinking.

Well some of us are doing things to eliminate contrails ... (Shameless self promotion of my employer)
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