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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Turn off the streetlights! It only helps the bad guys see better as they go about their appointed rounds. If that would save 10% of our electricity waste, so much the better. As an astronomer, I can only be grateful that Tucson has some night illumination standards, however inadequate to the purpose. Good grief, people, aren’t we trying to make this a better world? This is a no-brainer.
TomRude says:
March 3, 2011 at 8:31 pm
Outdoor lighting left on gives the criminal the ‘edge’ they need.
Real security takes place when motion trips the light and someone is paying attention.
Most crime occurs under the glare of outdoor lighting, as criminals are well aware that the lights are on, but nobody’s home.
The problem you have with security is that you expect a dumb device to take the place of safeguarding by a real person.
Even a silent alarm at a business is of no value unless someone responds quickly.
Obviously we need to paint all our streets and parking lots bla… oh, wait… we just were told to paint them white.
OK – got it. We need to require all exterior light be directed horizontally. Horizontal, then, shall be the direction. Down shall not be the direction except that the direction shall proceed directly to horizontal. Up is right out.
And the people cheered and sang and prayed there be more. On to the ears of he who hears all prayer and every utterance fell these words and he heard. Moved by joy welling within his divine being he spoke unto the throngs there gathered and said – “I’m cool wi’ dat.” And across the land there ushered forth his ministers and magistrates of horizontal light and he saw it was good and said – “Yiminy, dots goot! Let der be dem der LIGHTS!”
This will be used as an excuse for an energy saving campaign, lots of countries in the same boat as the UK with insufficient energy infrastructure planning.
http://www.bishop-hill.net/blog/2011/3/3/the-third-world-ambition-of-the-uk.html
For stating the bleeding obvious, this study ranks up there with that “animals feel pain like humans” study , but without the cruelty.
I live in a city where there are no working street lights, among many other things, and I can tell you driving in traffic without them is very difficult and scary. You can’t see road markings, the other guy on bright really makes it hard to see pedestrians, stopped cars, pot holes and so on.
I hate the light pollution but without it a city is somewhat unworkable. Fortunately I also enjoy astronomy so having been handed lemons I have made lemonade and don’t go driving after dark.
I live in Scandinavia at about 60 degrees North. Here we have “Light Pollution” all night long, every night in summer. Somehow humans (and everything else) have managed to survive this for thousands of years. As a matter of fact we love our “white nights”, it’s the dark days of winter when there is hardly any daylight at all that that are bad.
@tty March 4, 2011 at 12:16 am
Well, I live here too, and I am an amateur astronomer. The light pollution issue is a real problem and getting worse.
We only have short windows of real darkness in September/October and ~April if there is no snow on the ground and clear skies (which means almost never). In the summer season the natural light is too bright (given our location at 60N), but in the wintertime when it should be real dark it isn’t, due to reflection of high power artifical lights in the snow and atmosphere. Often you can’t see many stars at all.
Recently, a local football field was given new lights about 2km from where I live and ~120m below me, behind a hill. It still ruins the whole eastern sky with a giant “reflection column” that can be seen even from inside my house when the indoor lights are on.
The issue of light pollution (or whatever you call it) seems to have drawn out some very divergent views here.
As an amateur astonomer, living in a city, I expect the night sky to be lighter than if I lived in the middle of nowhere. I don’t expect all lights to be turned off, and I don’t think that this is what dark sky campaigners are asking for.
What I object to is lighting that makes the situation worse for no apparent benefit. Examples are things like lighting church steeples, advertising hoardings brightly lit all night. The other main culprit is poorly directed/shielded street lights. Having my bedroom illuminated by the light outside does not protect me from robbery, mugging or rape, nor does it stop my car being broken into. All it does is waste money.
More alarmist rubbish. Light pollution is only a problem if you wish to see the stars but with 8/8 cloud cover it does not matter where you are they are hidden.
First off – I’m a photographer. I really like astrophotography and spent a lot of money and effort learning that very difficult craft. So there is my bias, up front. Until recently, I did all my astrophotography from my backyard. Some of the equipment:
http://www.josesuroeditorial.com/Other/Landscape-Posts-2010/10867502_arm9E/2/1133582566_fcPtD/Original
http://www.josesuroeditorial.com/Other/Landscape-Posts-2010/10867502_arm9E/2/1133586962_uzC9T/Original
You can see some of the work I’ve done out of my back yard below – some of it requiring two and three nights of exposure:
http://www.josesuroeditorial.com/Astro-Photography/Nebulae/1138689_654sw#54459786_UVUez-O-LB
and,
http://www.josesuroeditorial.com/Astro-Photography/Galaxies/1166172_Fvc2U#54462311_fQtJH-O-LB
Sadly, with the real estate explosion that came at the beginning of this century I am no longer able to do those images from my backyard unless there is very low humidity in the air – a very rare thing here in Florida. The additional thousands of lights now in my neighborhood overpower the faint signal to noise ratio of these very dim sky objects. Colors are also completely distorted because a lot of the lights have a very narrow spectrum. It’s not the lights really, it’s the design of the lights. Most light fixtures throw 30 percent or more of their light upwards, where it’s not needed at all.
And yes, lighting the night and feeling safe because if it is in our DNA. No problems there. I just wish it wasn’t pointed where it is not needed. We humans have reasonably good night vision. With dark adapted eyes we can see really well after Sunset. The problem is that we light the inside of our homes so well that when we step outside our eyes are not adapted and we are basically blind. So, we use a lot more light outside than we really need because of this adaptation problem. I see no solution to the problem so I just don’t do much astrophotography anymore, and all that equipment has now become very expensive living room adornments – sigh.
Best,
Jose
I recently took up astronomy but was bugged by a street light. After a phone call to my county council highways department a nice man came and painted black the side of the lamp that faced my property. Not a complete solution but a vast improvement that was cheap and efficient. There is some common sense to be found in local government.
Dr. Dave says (3/3/11 at 8:52pm): …”On a moonless night it’s darker than the inside of your hat. I received a notice from a law firm that alerted me that I was to immediately remove the flood lamps mounted on my garage.”….. “This is personal to me because a few months later I was taking my recycling out to the street in the pitch dark, tripped, fell and broke a rib. I remember laying on my back that cold November night thinking “Gee…the night sky sure is beautiful!”.”
The joys local politics! If you happen to have a relative who is an attorney you might find it kind of fun to sue the city for your medical bill- i.e. the rib. I leave my spot lights on all night long (CFL’s to save energy). I love your approach to the problem (find a way around the rules) by the way. The bright lights on my truck have come in handy a few times when we have lost power- to light the path between our buildings.
We have some rule out here in the foothills of CA on how loud your generator can be…………. I’ll bet you are going to have a similar law soon too.
Extremely simple means to reduce night-sky pollution & still maintain ground illumination. Construct the outdoor lights to have their horizontal bottoms illuminated only (no light emitted sideways). Boxy looking, but much more efficient & light pollution is greatly reduced.
Light pollution is a problem for astonomers, and it is real. The media in the UK looked at this topic a couple of years ago. Streetlights for example should light the streets, cannot fault the logic. If we are wasting 30% of their oputput, shining up at the clouds we are nuts, why is there not a correct design of streetlight? more light where it is needed, less power required? less cost? am I wrong?
LED street lighting is available and lights only the areas needed, I think it was a smart councillor in Hawaii a few years back? replaced the towns lights with leds, he saved the council millions in power bills and replacing the burnt out bulbs, and sure would have reduced the “pollution” of the night skies as a bonus.
where I lie in Aus as above stated by others at night in rural areas we get magnificent starry nights, you really do feel you can reach up and touch.
you can also get very lost, fall and injure yourself with little effort, a torch isnt a toy its a necessity.
Blimey, there short-thinkers here. Leaving aside the question of who funded the research (and the one about whether or not the researchers are trying to jump on a gravy train… ’cause that would be a first, wouldn’t it?), let’s go through a few points, from the point of view of someone who grew up in London, then the Sussex countryside in England, and has since lived both in major cities and the pitch-black countryside:
1. Streetlights are still necessary for roads, even with every vehicle having headlights (assuming the fine, upstanding occupant remembers to turn them on), as the major problem with unlit roads are high-contrast shadows cast by the vehicle’s headlights, and glare from other headlights. Stuff can hide in shadows… like people, animals, stone walls, precipitous drops, etc. Good lighting can reduce the contrast to the point where the average human eye’s dynamic range is sufficient to extract detail from the shadowed areas.
2. There are no studies (and there have been a few, and no, I’m not going to cite them here, as it’s still early – Google is your friend here) that show positive correlation between higher illumination levels and reduced crime levels. Streetlights and other high-output lighting (so-called “security” lights) make people feel safer, but that’s about it. In fact, what they really do is provide deep shadows for the naughty people to hide in… see point 1 above (and ask me how I know after years of living in brightly-lit cities). The converse is that in the pitch-black country night, you learn to carry a torch, for crying out loud! That’s just common sense. It also means that naughty people would have to do the same, unless they’re wearing night-vision gear, making them stick out like a sore thumb.
3. “Natural” light pollution… oh, come on! In Scotland (where my family is from), you can read a newspaper by the light of the night sky in the summer. The closer you get to the poles, the more light there is during the summer months. Fact of life. This does not equate to the twerp next door deciding he’s going to mount a 500 watt “security light” on the side of his house, set in such a way that you never actually need to turn on the lights inside your own house. If I lived in Scandinavia, my circadian rhythms would adjust (just the same as they do after flying over a few time zones), but they can’t adjust to Dave next door turning on the light when he feels like it. Nor should they have to.
4. Final point: look at the photo of Chicago above. If you’ve complained about the funding for the study, realise this – these are your tax dollars/pounds/Euros being wasted. Simple as that. It’s got nothing to do with “warming the planet” or other such tripe. It’s just waste. You don’t leave the engine running when you’ve parked the car, or drive in the lowest gear possible, or leave the ‘fridge door open, or the water running, because these all cost you money. Why does anybody in their right mind thinks it’s OK to throw away two-thirds of a paid-for service?
Sorry if any of you feel ‘trivialised’ in any way by this. Actually, no I’m not. This is an issue by and of itself, and frankly some of the arguments here have been laughably juvenile, and do not do justice to the generally higher tone of comments this site usually enjoys.
It’s really bad when there’s snow on the ground. Frightening!
S T O P
I think, this is not the point of Anthony’s article.
Tim Ball says:
March 3, 2011 at 3:46 pm
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/
It’s more about this salient point!
Higher light “pollution” could be a reason for increased GISS data.
As they’ve abandoned rural stations, the urban stations show more light and therefore
interprets to higher temperature.
We should discuss THIS theme.
There is an easy way to darken the night sky, rely on sun and wind for power.
I could have told them that, on overcast nights, the clouds reflect the artificial light making it brighter in my suburb. Where to I send for my funding cheque?
Following up on Bloke down the pub’s comment, we had a very similar experience.
We bought our dream house with large gable windows across the front. It was not until our first night in the house that we realized the streetlight in front of our house shined through the windows all night long. I called the city maintenance department and they immediately retrofitted the streetlight with a conical shroud that completely eliminated the problem. The previous owners had just lived with the problem for twenty years.
Most of the older streetlights were poorly designed and didn’t constrain light to a downward direction. This is easily rectified in most cases.
As for those saying this is a serious problem, get a grip. Malaria in Africa, narco-terrorism in Mexico, and the US budget deficit are serious problems. This is an annoyance. Just because it bothers you doesn’t make it a problem for the rest of us.
Ref – Creepy says:
March 4, 2011 at 7:55 am
You’re on! This is one of a number of problems with Hansen, et al; the science really isn’t very settled at all. Noise pollution is another problem with Hansen that hasn’t “hit the fan” yet.
What a beautiful photo! Absolutely incredible! Congrats for bringing this to attention.
“…the amplification of light pollution by clouds is large, and should be taken into account.”
The clouds do not amplify, they reflect. So these nerks can’t even think straight. It did say “physicists and ecologists.” Maybe (optimistically) the physicists didn’t write the report. No wonder the talk about positive feedbacks from water vapour.
@Allan – The post says “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,”
The impact of reflection from the same cloud bank was an amplification over the clear sky luminance of either a factor 3 or 10, depending on where it was measured. It’s not like clouds in the city can reflect three times as much light…
Also, regarding why light pollution sucks, even if you don’t like to look at stars – light pollution is suspected to cause health problems, by screwing up melatonin production:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627884/
or here: “We found a significant positive association between population exposure to light at night and incidence rates of prostate cancer, but no such association with lung cancer or colon cancer.” Read More: http://informahealthcare.com/doi/abs/10.1080/07420520802694020
There is also new evidence from mice that suggests light pollution might also be a factor behind the obesity epidemic.