Author Topic: Selective Memory  (Read 2182 times)

ontoolhaiworl

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Re: Selective Memory
« Reply #30 on: January 25, 2018, 10:48:07 PM »
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This subject comes up on occasion, and at least the answer for Flagstaff, AZ is yes. Brian Skiff has been recording cloudiness data since the late 1970's. While there are many in the Southwest U.S. and California who are convinced that cloudiness has become worse, there is actually no such trend. The annual and nightly summaries may be found here:
http://www2.lowell.e...ata/clouds.html

The plot of the annual data below ("photometric" + "partial" nights) looks pretty flat. Note that here in the best astronomy climate in the country, only slightly better than one night in three is clear.I can't speak for New England, but at least in my region, the notion that the weather is degrading is indeed another case of pessimistic, selective memory. As I age, I notice that my contemporaries tend to remember many aspects of their past as being better better than they really were.

Tom
Thanks - I still haven't found a good reference but I see a number of studies that show a slight increase over the last decades - but nothing like the impressions some people have of how much worse things are today.

I think a lot of the thinking is caused by a reactionary mindset - everything was much better years ago - in addition to an element of pessimism.

But just sitting down and looking in your head and making a subjective assessment of something now compared to years ago isn't very scientific. And even if you take notes over the years, there are multiple layers of selection going on.

From what I can tell, if there is a trend it is small and the errors of human memory and subjective judgement are much larger.

Frank

Aaron Maggot

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Re: Selective Memory
« Reply #31 on: January 31, 2018, 08:45:23 AM »
All I can say is I was out there observing at least an hour every day for that run of nice days we had with no moon.
The first few days of that period looked clear but had smoke issues from the fires out west plus some local fog.
The last few days were much, much better. Glad to here there is more good weather coming.

nonbuysalcho

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Re: Selective Memory
« Reply #32 on: January 31, 2018, 12:21:46 PM »
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I don't know of a good source of data for nighttime cloudiness over the past decades. It would be great if such a thing existed. I think there are good records of cloudiness during the day in many regions - but not so much for the night.

Does anyone know of a good source of nighttime cloudiness measurements done in a systematic manner over the past, say - 50 years, for some location?

Professional observatories should have that - but they tend to be on mountain tops and in areas with clear skies in the first place.

I hear people in both northern and southern hemispheres saying that the skies are cloudier than they used to be. But is there any systematically taken data to back it?

Observing logs don't really count unless a log is taken every hour of every night.

Frank


This subject comes up on occasion, and at least the answer for Flagstaff, AZ is yes. Brian Skiff has been recording cloudiness data since the late 1970's. While there are many in the Southwest U.S. and California who are convinced that cloudiness has become worse, there is actually no such trend. The annual and nightly summaries may be found here:

http://www2.lowell.e...ata/clouds.html

The plot of the annual data below ("photometric" + "partial" nights) looks pretty flat. Note that here in the best astronomy climate in the country, only slightly better than one night in three is clear.I can't speak for New England, but at least in my region, the notion that the weather is degrading is indeed another case of pessimistic, selective memory. As I age, I notice that my contemporaries tend to remember many aspects of their past as being better better than they really were.

Tom


Hold on there just a minute, brother Tom. Citing cloudiness tends for an area likely to historically be the one of the least cloudiness prone and near desert-like environments in the U.S. to begin with can hardly be assumed to translate to the prevailing situation across the rest of the nation. That's just pure nonsense. I can give you similar such statistics for the Northeast from my own detailed records that are absolutely 100% the opposite and can go back even further to the early 1960's! Neither do I need to just assume that my figures are applicable elsewhere when 95% of posters all report the same depressing trends, regardless of whether posters can produce representative graphs detailing such, or not.

BrooksObs


adrajacte

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Re: Selective Memory
« Reply #33 on: February 02, 2018, 06:08:04 PM »
Here's a pretty good write up from 1974 to 2004 - but it only uses daytime cloudiness.

http://journals.amet...5/BAMS-87-5-597

Very noisy trends with uncertainty in the measurements - but perhaps a 1.4% increase per decade - maybe.

Other results from ISCCP suggest a decreasing trend - but may be a sampling artifact:

http://www.nature.co...ws070219-5.html

It seems to me the people who feel strongly that cloudiness is increasing would say so about both day and nighttime cloudiness - so just using daytime should be ok. But if the claim is only that nights are more cloudy - I don't know a good study for that.

Frank

contreleri

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Re: Selective Memory
« Reply #34 on: February 02, 2018, 09:29:39 PM »
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I'm wondering exactly what passes for a "clear night?"

Those numbers seem low for what I would call "observable" nights for the coastal range east of San Diego.

Jon

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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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Re: Selective Memory
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