Non aviation content. Play nice – No religion, no politics and no axe grinding please.
By oldbiggincfi
#1755373
This morning, living in SE England , I woke to clear blue skies.
Very bright sunlight and a lot of sunshine warmth.
Not a contrail to be seen .

Are we going to experience increased surface temperatures as a result ?
What about solar panels - will they produce more ?

There is also a noticable difference in backround noise, few aircraft , and much less road traffic .

Thoughts please .
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By mmcp42
#1755398
Robin500 wrote:Yes, Greta will be delighted.

according to the fount of all knowledge (the Daily Wail), Greta is self-isolating due to showing symptoms of Covid19
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By Genghis the Engineer
#1755403
oldbiggincfi wrote:This morning, living in SE England , I woke to clear blue skies.
Very bright sunlight and a lot of sunshine warmth.
Not a contrail to be seen .

Are we going to experience increased surface temperatures as a result ?
What about solar panels - will they produce more ?

There is also a noticable difference in backround noise, few aircraft , and much less road traffic .

Thoughts please .


The science has been ambiguous on this for a while, but creeping up on making sense. The leading researchers in the world right now are two professors, one in Reading - Professor Keith Shine, and one at DLR in Germany, Professor Ulrich Schumann.

If you look at the IPCC (International Panel on Climate Change) reports you'll see that one of the biggest error bars is over aviation's contribution to radiative forcing (the basic mechanism by which the troposphere is net warming), and that is down in large part to contrail-cirrus.

The mechanism there is that contrails form through ice crystal formation around sooty particles emitted from aircraft exhaust during flight through regions of air supersaturated with respect to ice (that is the air is above 100% relative humidity, and below 0°C). Some contrails don't last, some persist, and some persist and grow - becoming contrail cirrus.

Contrail cirrus is believed to have two opposite impacts upon radiative forcing. In the day it is net cooling because it tends to reflect solar radiation : a mixture of short and long wave radiation back into space. At night however it tends to reflect emitted long wave (heat) radiation emitted by the earth's surface back into the earth - which is net warming. Now one obvious impact is that this gives cooler days and warmer nights locally, but the question here is about net warming or cooling.

That's the much tougher question, and I'm only on the fringes of this science, but my understanding is that the scientific consensus is heading towards a net warming effect. This means that aviation's contribution to anthropogenic climate change is probably closer to 4% of the recent total, rather than the 2% we've mostly been told (bad), but does mean we're starting to understand the problem a lot better (good).

So right now, the grounding of most, but not all, flights has probably removed about 3% of mankind's contribution to climate change.

G
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By Miscellaneous
#1755411
oldbiggincfi wrote:Thoughts please .

Stepping back from the detail and considering the big picture.

If we consider global warming is measured in low single digit degrees C over decades I doubt we are going to notice the influence of reduced aviation ( to use G's No. 3% contribution) over a couple of months given the daily fluctuations in weather.

I wonder if the reduced pollution from all sources through this crisis will even offset the pollution from the Australian fires?
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By Paul_Sengupta
#1755419
Global warming/climate change isn't the immediate question asked though.

Assuming day time local temperatures are asked for, will it now be warmer, at least on cloudless days? I'd have thought it would be. It'll be colder at night, though there aren't that many flights overnight anyway, so it might not be much colder.
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By Miscellaneous
#1755430
I'd suggest it's the same thing @Paul_Sengupta, I was using the idea of global warming to highlight some relative numbers re the influence of pollution. The daily fluctuations are of course much greater for any given location never mind across the country. I doubt any difference would be detectable and determining any difference due to aviation very difficult.

Having a look now on Windy.com shows Bristol at 12 degrees and Thurso at 7 degrees. Not a great difference today. However for temps to be noticeable I'd think the influence of aviation would have to be much greater than it is. To extrapolate a detectable influence over a couple of weeks to the effect on long term global warming (+ve or -ve) I think would require a pollution source much greater than aviation.

What sort of fluctuation would be required to be detectable and how could that be determined to be due aviation and not weather?

Not backed up by science, just my thoughts as requested. :wink:
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By Paul_Sengupta
#1755446
PaulSS wrote:Didn't we do all this bolleaux before with the volcano?


And before that with 9/11, at least in the US. There were figures going round saying it was on average 1 degree C warmer in the day and correspondingly colder at night in the days after. Whether it was true or not I have no idea.