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comments about climate change and observation

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comments about climate change and observation

dear Sirs, I'm writing an article for the Russian popular publications on how to change the astroclimate in connection with global climate change. If you have the experience of long observation, I will be grateful if you share your comments. changing the number of days when you can see deteriorated transparency of the atmosphere, increased the number of cloudy days. and any other of your comments.

lmk's picture

I have been observing for nearly 20 years. I think its very difficult or impossible to answer your question about how global climate change may or may not affect ground-based astronomical observations. I do not keep detailed weather records of all my observation times and places, and I have observed from different parts of the country over that time period. I doubt other observers keep detailed records of sky conditions, though a few may do so.

Overall, considering typical random variations in weather over the days, months, years, I cannot report any noticeable pattern, worse or better, which I would attempt to associate with climate change over the past 20 years.


thank you for answer, Mike.

thank you for answer, Mike. could you say, where is the best place for observation? and did you remark the influence of atmospheric turbulence?

lmk's picture
Hello Natalia, Well the best

Hello Natalia, Well the best place for observation is the top of Mauna Kea, HI :) But, of course, as an amateur observer, I am stuck with more usual places to use. I have observed about equally from California and Hawaii, and both can have very excellent conditions, sometimes poor conditions, though I would say Hawaii has the better seeing, least turbulence on average, especially on the windward side of the islands.

California had several years of drought, until last year was extremely wet, record snow and rains! So, it seems to me, as a casual observer of the weather, that the shorter term changes due to oceanic water temperature, the El Nino and La Nina effects, dominate the patterns here more than the longer term climate change. So, in short, it is really tough to judge if any long term changes might be occuring when the yearly changes are so great!

Another example of how local effects can dominate global effects, is the air pollution, "smog", which Los Angeles is world famous for... Back in the 60's, 70's it was pretty bad, I remember as a child how polluted the air was, how it prevented any sort of realistic astronomy from the city areas. But, in the last 10 years especially, the results of the very strict pollution controls, the air has improved dramatically. Many recent days can have nice clear blue transparent skies, and even astronomical observations can be reasonably accomplished from the LA basin. We have several AAVSO observers who very successful at this, something which likely would have been impossible throughout most of the 20th century.

So, the LA history shows that the terrible things humans have done to our environment in the past, can be undone with concerted effort :)


stellakafka's picture
light pollution?

Hello Natalia,

The one way climate change has affected ground-based observations is that, with changing weather patterns, observing locations that were considered "premium" because of clear skies are suffering from unwanted bad weather. As Mike mentioned, this is difficult to quantify...

One of the factors that have strongly affected observing sites is light polution - bright lights usually in urban areas that increase the background of the sky and prevent us from seeing fainter objects. There are many discussions on how delevopment has affected dark skies, and what can be done about it, and I'll be happy to point you to several relevant studies. You should be able to find ample web pages with relevant information about this ...

I hope this helps.

Best wishes - clear skies,


Dear Stella, can you tell me,

Dear Stella, can you tell me, hoe change premium location?

BRJ's picture
Climate Change and Observations

Hello Natalia. I can perhaps offer some modest insight into apparent "climate change" at least for my particular region of the United State, namely the U.S. Northeast (southeastern New York State). I would guess that I am one of the organization's longest and most active members, having begun reporting data more than 50 years ago (1963). Over the course of that interval I have submitted more than 212,000 visual estimates, which I believe puts me in a rather good position as a judge of weather trends for my area. I would add that I reside in a semi-rural location about 75 miles (120 kilometers) north of New York City.

Without question my observing records indicate a slow, but very steady, decrease in the number of clear nights available to me per year, even through after retiring nearly two decades ago every night was available to me for observing. In the distant past (pre-1980-1985) it was common to experience successions of clear days and nights, perhaps 3 to 5 and sometimes more in a row. This virtually no longer occurs here, especially in the past few years. At best we now get only 1 or 2 clear nights at a time, often followed by 4-5 days of poor weather. Further, winters have become milder and cloudiness (without rain or snow) much more common. At the same time, cool summer nights have vanished.

Two distinct and what I regard as highly unusual and interesting phenomena occurred in recent years and are perhaps worth noting. The first one I became aware of began slightly prior to 1990 and just preceding the time of Mt. Pinatubo's eruption and the Gulf War. In that period the skies on clear days became noticeably less transparent, i.e. less intensely blue. Instead, the sky looked rather milky at all times.  Having long been involved in outdoor photography, I took particular note of this almost immediately. At first I associate this change in sky clarity in some manner with the two events cited above, particularly the first one as many wonderful atmospheric displays were seen (very colorful sunsets, prismatic bars at various points in the sky and Bishop’s Ring). I filled an entire journal with descriptions and drawings of the atmospheric phenomena that I observed. However, as the upper atmosphere eventually cleared of fine dust after a couple of years the deep blue skies, particularly common during our autumn formerly, have rarely been seen since.

The second event occurred during the several days immediately following the September 11, 2001 attack on the United States by terrorists. All air traffic except military was totally suspended for three days. This happened to occur during a rare extended period of clear weather here and over the three days following the attack I saw the clearest and bluest skies I had seen in more than a decade and the nights were unusually transparent and dark. Coincidence perhaps, or maybe a lack of aircraft contrails? I cannot really say, but others noticed this as well throughout the country where it was clear. It was even recorded at scientific monitoring stations in California. After commercial air traffic resumed conditions quickly deteriorated back to their former state.

Overall, I would venture that the number of usable nights has decreased by AT LEAST 1/3 over the years and many of those that I use nowadays I would likely have passed on in earlier years. Other observers, including those less active than myself, often comment on the rarity of clear nights these days during our on-line discussions.

As a final note, let me add that I was very good friends for many years and was mentored by the late Edward Oravec, one of AAVSO's all-time leading observers. He had begun his AAVSO observing career around 1940, thus preceding my own by about a quarter century. In a discussion with me concerning observing conditions/clear nights he remarked (in the late 1960's) that he had noticed the number of clear nights steadily declining in the course of his long observing career!

John Bortle   (BRJ)

thanks a lot

Dear John, you save my article. just one russian scientist said about less row of clear night. the observation have a statistics, but i cannot find general stat of several years, and its very interesting, how gulf affects on ability of sky observation. russian amateur, who use internet and can move from one point to another are very young and have 5-7 years observation experience.


dhdeangelis's picture
A warmer ocean, a warmer atmosphere, and aviation contrails

I agree with John's perspective. A warmer ocean, a warmer atmosphere, and aviation contrails (that act as cloud seeds) all conspire to increased cloudiness. Clouds are, however, among the most difficult aspects of climate science, and establishing an unambiguous connection between increased cloudiness and oceanic/atmospheric warming is not a simple task. There is nevertheless plenty of scientific evidence that cloudiness is increasing, for example in Canada. Recently, I also did a simple analysis of cloudiness data from Stockholm (Sweden) and the data show that cloudiness is indeed increasing, which is consistent with a warmer climate. You can have a look at this little study (and reference to papers on Canadian cloudiness) in my astro website:

Is cloudiness increasing? The curse of cloudiness and climate change

Feel free to comment, here or in the site's comment fields.


Hernán [DHEB]

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