Clouds amplify ecological light pollution
The brightness of the nightly sky glow over major cities has been shown to depend strongly on cloud cover. In natural environments, clouds make the night sky darker by blocking the light of the stars but around urban centers, this effect is completely reversed, according to a new study by a group of physicists and ecologists at the Free University of Berlin (FU) and the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB).
“We found that overcast skies were almost three times brighter than clear at our rural location, and ten times as bright within the city itself,” says the lead author of the study, Dr. Christopher Kyba, physicist at the Institute for Space Sciences at the FU. Their research was reported on March 2nd, 2011, in the open access journal PLoS ONE.
“The astronomers who founded the study of light pollution were concerned with how sky glow obscured the stars on perfectly clear nights,” says Kyba, “and researchers studying the potential influences of sky glow on human or ecosystem health often cite the results from satellite measurements taken on clear nights. What our study shows is that when considering biological impact on humans and the environment, the amplification of light pollution by clouds is large, and should be taken into account.”
The study compares measurements of clear and cloudy sky brightness data taken using “Sky Quality Meters” during five months in the spring and summer of 2010. Two monitoring stations took data at locations 10 and 32 km from the center of Berlin. “Recognition of the negative environmental influences of light pollution has come only recently,” says Dr. Franz Hölker, ecologist, study author, and project leader of Verlust der Nacht (VdN – Loss of the Night).
“Now that we have developed a software technique to quantify the amplification factor of clouds, the next step is to expand our detection network. The Sky Quality Meter is an inexpensive and easy to operate device, so we hope to recruit other researchers and citizen-scientists from around the world to build a global database of nighttime sky brightness measurements.” The authors encourage those interested in participating in such a measurement to contact them at sqm@wew.fu-berlin.de.
The research was funded by two interdisciplinary projects, MILIEU (http://www.milieu.fu-berlin.de/en/index.html) and VdN (http://www.verlustdernacht.de/index.html). An interdisciplinary project of the FU, MILIEU – center for urban earth system studies, was initiated as a focus area at the FU, funded by the German excellence initiative, in order to investigate the bottom-up and top-down interactions between urban agglomerations and the climate and environment. The VdN project, funded by the German Ministry of Education and Research, is specifically devoted to quantifying light pollution and investigating its impact on humans and the environment.
Citation: Kyba CCM, Ruhtz T, Fischer J, Ho¨ lker F (2011) Cloud Coverage Acts as an Amplifier for Ecological Light Pollution in Urban Ecosystems. PLoS ONE 6(3):e17307.doi:10.1371/journal.pone.0017307
PLEASE LINK TO THE SCIENTIFIC ARTICLE IN ONLINE VERSIONS OF YOUR REPORT (URL goes live after the embargo ends): http://dx.plos.org/10.1371/journal.pone.0017307
Competing Interests: The authors have declared that no competing interests exist.
Funding Statement: This work was supported by the project Verlust der Nacht (funded by the Federal Ministry of Education and Research, Germany, BMBF-033L038A) and by MILIEU (FU Berlin). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Contact information:
Dr. Christopher Kyba
Freie Universitat Berlin / IGB
+49 30 838 71140
Available weekdays 1pm-4pm (CET), evenings possible by email arrangement
christopher.kyba@wew.fu-berlin.de
http://userpage.fu-berlin.de/~kyba/
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Is it kind of hard to see the stars with lots of clouds even if they don’t make it brighter.
Light pollution? Actual problem or a clever pun? You decide.
Anybody who has been outdoors at night in a city knows the sky is brighter when it is cloudy than when it is clear. Who exactly is paying for this?
This is news? I was 12 years old playing outside in Denver colorado and noticed on an overcast night how much easier it was to see everyone when we were playing Hide-and-Seek. That was over 30 years ago.
Maybe I should apply for a retro-active grant?
Short of installing shades/reflectors on all streetlamps, there doesn’t seem to be any sort of remedy.
This does not surprise me. I’ve had to install blackout blinds in my bedroom to keep out light pollution and get a good night’s sleep, otherwise I wake through the night thinking it’s dawn.
Anyone else suffer from lack of sleep due to light pollution?
I’m not sure that I understand the negative impacts of light pollution. I know that I can see better when I return home after dark if it’s overcast, but I don’t see the problem with that.
“Ecological light pollution” is a quality judgement and hardly has a place in the title of a scientific paper. Light scatter may be closer to the mark. As a sometime amateur astronomer I can appreciate clear skies, but don’t start a paper with an obvious bias.
What does this do to Hansen’s night-light brightness measure of the urban heat island effect? http://www.giss.nasa.gov/research/news/20011105/
Is this for real. This is 2011 and people are getting paid to tell us that in the city clouds make it brighter. Dah Dah Dah. I dont think this is ground breaking news.
News flash : WHen there are no clouds in the sky it doesnt rain. WHen there are clouds in the sky it sometimes rains. Can i get a grant to study this?
No S*** Sherlock!
I’m guessing that the next set of taxpayer-funded studies will examine how the ecological balance has tilted so that former daytime-only predators can now hunt effectively at night, ‘catastrophically changing’ the ecosystem (the scientists will have forgotten about how day length changes over the course of a year–it’s called ‘seasons’).
Then there will be studies linking this to crime (more? less? The answer is cloudy… 😉
Then there will be something about clouds converting light to heat and melting the glaciers.
And so on it goes. Sheesh.
Here in Florida, I have been looking at highway cloverleaf lighting. It seems to me that a great deal of energy is wasted illuminating highway ‘landscaping’ (IMHO, that is an sad misnomer) and that a back-of-the-envelope estimate would be 60-75% wasted power lighting things that would prefer not to be lighted at night.
For what it’s worth, anyone who lives in a big city and looks up at night can see the fact that light from the city goes upward. I even shot a timelapse video of it:
or
I’d really love to know what harm comes from this? If you want to see stars, go to the countryside.
“The astronomers who founded the study of light pollution were concerned with how sky glow obscured the stars on perfectly clear nights,”
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Astronomers, who needs them 🙂
On the internet, there is an image of a stitched together map of artificial light seen from space at night time. It is also a map of human prosperity. I am somewhat sad to say that my neighborhood, I4 across central florida, is prominently displayed. Yes, there are lots of lights along I4 and Florida’s low flying clouds reflect them powerfully. It is difficult to see stars on clear nights. However, it is hard to see how the light reflected from clouds would be noticed by critters travelling among the lights on the ground.
So What?
This is actually a beneficial effect in suburbs without streetlights, such as Saratoga, CA: more useful light for the same energy use, without the capital outlay for more streetlights. We need more night clouds.
Except on meteor shower nights, of course. 🙂
Keith Minto says (March 3, 2011 at 3:43 pm): ‘“Ecological light pollution” is a quality judgement and hardly has a place in the title of a scientific paper.’
Next thing you know, the EPA will go after the moon for “light pollution”. 🙂
It has to be a joke right?
Light pollution ??? hahahahahaah!!!
Same thing as animals exhaling produces pollution ehh …
Astronomers are rightly concerned about light pollution. However, …. WE’RE ALL GONNA DIE!
Those researchers never heard of the light conditions inside the polar circles. Damn sun is polluting 24/7 for 6 months in a row in these area of the globe.
My wife and I have an older Bausch & Lomb 6000 Telescope and we happen to live a bit out in the country- no streetlights, box store parking lot lighting. etc- which makes viewing the stars more enjoyable at our place then in the SF BAY AREA. If your really into star gazing you might find this of interest- “Stargazers now have their Graceland. The Channel Island of Sark, located 80 miles south of England, has been designated as the world’s first dark-sky island.” as noted- http://www.buzz.yahoo.com/buzzlog/94259
Could there be a light dimmer company lobbying governments for cities to install dimmers on cloudy nights?
That should be a good place to put a change a light bulb joke…
Q. How many climate scientists does it take to change a burnt light bulb?
A. None. The computer model says the light is not burned.