On 14/01/2021 13:53, Martin Gregorie wrote:
> On Thu, 14 Jan 2021 10:26:59 +0000, Ahem A Rivet's Shot wrote:
>
>> On Thu, 14 Jan 2021 05:48:16 +0000 The Natural Philosopher
>>  wrote:
>>
>>> (iii) Its down to high flying aircraft contrails, so we should just
>>> stop flying.
>>>
>>> Of these the only currently  *testable* one is (iii) and when air
>>> transport did shut down post 911 there were in fact colder nights in
>>> the USA. And post Covid 19 shutdown there has been a rather cold
>>> northern hemisphere winter.
>>
>>  I've seen comments that during the 911 flight shutdown the average
>> temperature over the US rose a little. I have no reason to doubt either
>> that observation or yours, it is just an indication of how difficult it
>> is to test even that hypothesis - let alone ones like "It's a mix of i
>> and ii proportions unknown". Personally I don't believe anything that
>> ascribes a single cause to a complex phenomenon because I ain't seen one
>> yet.
>
> Its quite possible that both are true and that both are due to the same
> cause - the absence of jet transport contrails over the continental USA:
>
> - daytime temperature rose and the skies looked clearer because there
>    were no contrails reflecting sunlight back into space. NOAA reckon that
>    average daytime temperatures rose by 3 degrees Fahrenheit during the air
>    travel shutdown and many American glider pilots commented, in
>    rec.aviation.soaring, on how much clearer the air had been.
>
> - I assume the same happened at night, but it would work in reverse, with
>    the lack of contrails at night allowing the ground to cool more because
>    they weren't there to prevent heat from radiating out through the
>    atmosphere. I don't remember seeing any comment about this though, or
>    seeing any estimate of what the temperature drop was.
>
>
in an effort to get a handle on the net effect I looked at the *average*
temperatures in cloudy humid florida and in dry desert sahara on the
same altitude.

They were pretty much the same...


--
“It is not the truth of Marxism that explains the willingness of
intellectuals to believe it, but the power that it confers on
intellectuals, in their attempts to control the world. And since...it is
futile to reason someone out of a thing that he was not reasoned into,
we can conclude that Marxism owes its remarkable power to survive every
criticism to the fact that it is not a truth-directed but a
power-directed system of thought.”
Sir Roger Scruton

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