Talk:Global dimming

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    [edit] BBC Horizon

    (William M. Connolley 23:40, 13 Jan 2005 (UTC)) All this surge of editing presumably comes from the BBC horizon documentary. Which is all very well, but basing your science on a TV programme may not be a good idea.

    Unqualified and unattributed editing would indeed be unwise. Checking all the sources used by the BBC would be a very good move, especially for such a potentially important topic; hopefully someone will have the time to do that. Wikipedia is, however a "work in progress" and should be treated as such. 80.42.86.119 23:53, 13 Jan 2005 (UTC)
    (William M. Connolley 00:04, 14 Jan 2005 (UTC)) Yeeeessss... but perhaps checking them *before* putting them in would make some sense too?
    Agreed, a practice I follow given the time to do so, especially if the source is less reputable than the BBC. Though I know even they are capable of getting basic facts wrong too...
    It's not so much that popular science media like the BBC aren't reputable or honest, but simply by dint of their programming priorites they produce material of a rather lower grade of factuality than that demanded by an encyclopedia. In particular, they're prone to:
    • picking the most exciting scenario from the range possible and concomitantly discounting the more prosaic.
    • downplaying controversy and dissent (except where the controversy is the subject of the piece, in which case they tend to overplay it)
    • willful conflation of correlation and causation
    The Sept 11th thing is a case in point of this last issue. It's true that there's a correlation between this particular cessation of contrails and a change in temperature; but this doesn't by any means prove a causal link. Worse, as we have but a single datapoint, the correlation is very weak. The article said "with a consequent sudden drop in global dimming", but that's a far stronger statement that the evidence supports. I reworded that paragraph to be much less conclusory. -- John Fader 01:34, 14 Jan 2005 (UTC)
    The question of checking sources is one I grapple with every time I want to edit the encyclopedia. To research everything to the level acceptable to, say, a degree level dissertation would simply mean I would never actually write anything given the time I have available.
    It's important, in my opinion, to judge whether the inexact and uncoroborated information will be of more value than nothing at all. Or that the good will outweigh the bad. Or something. The fact that anything written will be ruthlessly weighed and edited by others is reassuring in this context. Like the proverbial fountain pen, many articles on which I write soon contain little of my original prose - but are nevertheless shaped by all contributions to them.
    Btljs 23:32, 14 Jan 2005 (UTC)

    [edit] The 9/11 plane groundings

    When Horizon showed the graph before during and after the plane groundings the before and after (not during) had a noticeable difference so the difference in temperature was neglibleShiney 06:35, 14 Jan 2005 (UTC)

    • My guess is that they show very simplified graphics (i.e. three values on a bar graph) but that the analysis behind these results is somewhat more thorough and we are not given that in the programme. The researcher said that it had not been observed in 30 years so it can't be negligable - the point being the way it 'jumped' then returned to what was presumably a smooth curve if we had seen the whole month for example.

    Btljs 23:19, 14 Jan 2005 (UTC)

    Better references for this are:
    Travis, D.J., Carleton, A.M., and R. Lauritsen (2002). "Jet Contrails and Climate: Anomalous Increases in U.S. Diurnal Temperature Range for September 11-14, 2001." Nature, Vol. 418, p. 601. This is just a short communication . For 11–14 September 2001 the diurnal temperature range is 1.1 degrees C over normal 1971–2000 values whereas the three-day periods either sidehad temperature ranges near or below the mean. On average the diurnal temperature range for the post 9/11 period is 1.8 degrees C higher than the two three day periods before and after.
    Regional variations in US diurnal temperature range for the 11-14 September 2001 aircraft groundings: Evidence of jet contrail influence on climate, Travis DJ, Carleton AM, Lauritsen RG, JOURNAL OF CLIMATE 17 (5): 1123-1134 MAR 2004. Abstract:"During the 11-14 September 2001 grounding period natural clouds and contrails were noticeably absent on high-resolution satellite imagery", "the regionalization of the DTR anomalies during the September 2001 'control' period implies that contrails have been helping to decrease DTR in areas where they are most abundant".--NHSavage 22:06, 23 February 2006 (UTC)

    [edit] Ohmura article

    I can't find any publication by Ohmura in 1989, but he has four in 1990:

    • Ohmura, A., 1990: Reevaluation and monitoring of the global energy balance. Sanderson, M. (Ed.): UNESCO Source Book in Climatology, 35-42.
    • Chen, J. and Ohmura, A., 1990: On the influence of Alpine glaciers on runoff. Lang, H. and Musy, A. (Eds.): Hydrology in Mountainous Regions I, IAHS Publ., 193, 117-125.
    • Chen, J. and Ohmura, A., 1990: Estimation of Alpine glacier water resources and their change since 1870s. Lang, H. and Musy, A. (Eds): Hydrology in Mountainous Regions I, IAHS Publ., 193, 127-135.
    • Enomoto, J. and Ohmura, A., 1990: The influence of atmospheric half-year cycle on the sea ice extent in the Antarctic. J.Geophys.Res, 95, 9497-9511.

    I'd guess that the first one is the most likely to be the relevant paper. -- John Fader 20:09, 15 Jan 2005 (UTC)

    (William M. Connolley 21:02, 15 Jan 2005 (UTC)) Thanks. Now all we need is for someone to check the UNESCO book... incidentally, there is something by Ohmura in 1989 (O, Gilgen and Wild, but it looks like a tech rep not in a journal and may well be in German): Ohmura, A., H. Gilgen, and M. Wild (1989), Global Energy Balance Archive GEBA, World Climate Program—Water Project A7, Report 1: Introduction, Zuercher Geografische Schriften Nr. 34, Verlag der Fach-vereine, Zuerich, 62 pp.

    [edit] Theory behind the program

    (Ferdinand Engelbeen 20:20, 16 Jan 2005 (UTC))

    The theory behind the Horizon program, that more sunlight is reflected due to (sulphate) aerosols is at odds with measurements from space.

    For the (sub)tropics, in the period 1985-2001 the amount of sunlight reflected by clouds reduced with ~2 W/m2 in the tropics (20N-20S). (see: http://www.atmos.ucla.edu/csrl/publications/pub_exchange/Wielicki_et_al_2002.pdf, confirmed for the 30N-30S (sub)tropics in http://pubs.giss.nasa.gov/docs/2002/2002_ChenCarlsonD.pdf) In the 1985-1994 period, there was a loss of cloud cover, both in the tropics and subtropics (and even up to 60N-60S) of 0.33% and 1.7% respectively.

    If there is global dimming at the surface and no more reflection, the only explanation possible is that more sunlight is retained in the atmosphere itself. Which is possible with (dark brown and black) soot particulate. If soot particulate is to blame, then a reduction of it would have a cooling effect, not a warming effect.

    Another hint is the amount of reflected sunlight from earth on the moon ("earthshine"), which parallels the "global dimming" trend, while it should have an opposite trend, at: http://www.bbso.njit.edu/science_may28.html (main page at http://www.bbso.njit.edu/ )

    [edit] RealClimate

    I added links to two articles on www.realclimate.org on the issue. I don't have the time to work their content in, but they might serve as a good starting point for anyone who is going to dig in deeper.--84.151.204.4 12:19, 24 Mar 2005 (UTC)

    realclimate.org is a blog. However, I found Journal references for many of the links you provided. Thanks for your help.Kgrr 21:11, 11 March 2007 (UTC)

    [edit] Rm cooling effect

    (William M. Connolley 09:23, 27 Apr 2005 (UTC)) Somewhat in a hurry, I removed "This cooling effect may have led scientists to underestimate the effect of greenhouse gases on global warming." from the intro. I'm not really sure it *is* a cooling effect. Certainly a 5% reduction in solar would produce huge cooling, which would be obvious; since that isn't there, the (observed) solar reduction at the sfc is balanced by other effects - the same solar abs at higher levels; or diffuse.

    [edit] Effects

    (William M. Connolley 18:04, 16 May 2005 (UTC)) The effects section is completely unsourced. Is anybody fond of any of it?

    I have no fondness, but at least one Reference mentions "possible agricultural consequences", which suggests there may be some effects in references. (SEWilco 18:13, 16 May 2005 (UTC))

    [edit] Effect on Plants

    I have noticed that wherever global dimming is mentioned, it is coupled along with the "we're all gonna die" theory that many scientists seem to have adopted. Imagine that the Earth is a glass box with a small tree inside, and above there is a light bulb. The rate the plant will photosynthesize depends on the concentration of CO2 in the surrounding atmosphere, and the light intensity.

    So if you try and increase the concentration of CO2 in the box, the plant will start growing more quickly, and CO2 levels will drop.

    But if we introduced the global dimming effect (by turning down the light) then (surprise, surprise) the plant cannot photosynthesize as much as previously and is limited by the low levels of light. Therefore the CO2 level rises.

    Is this worth mentioning?

    Plants might even shed more CO2 than they split if they don't get enough light. Plants must burn caleries to live just as we do. I think I read somewhere that many types of plants will not grow as well if the CO2 levels get much higher. Marksda 00:30, 29 May 2006 (UTC)
    The problem is that this is all speculation. Light levels haven't gone down nearly far enough for this to occur. William M. Connolley 08:38, 29 May 2006 (UTC)

    [edit] Astronomy

    Not just plants - how about astronomy? Could global dimming relate to recent "discoveries" like distant supernova being "too dim" and thus provide evidence for "Dark Energy"? No reference yet that i know of. —The preceding unsigned comment was added by Smkolins (talk • contribs) on 20:42, 20 April 2006.

    This is completely unrelated to observations of distant light sources, including supernovae. Earth's surface is receiving varying amounts of light due to its atmosphere's composition changing. When observing sources outside the atmosphere, telescopes are calibrated against outside sources of known brightness. Also, at least some of the observations of distant objects were performed with space-based telescopes that aren't affected by Earth's atmosphere. --Christopher Thomas 21:00, 20 April 2006 (UTC)
    Changes in the sun are covered under Solar constantKgrr 16:37, 11 April 2007 (UTC)

    [edit] Effects on Oceans

    I can think of two components affecting the depth of light into the ocean

    • First- as the light coming through the skies have dimmed the depth to which light could penetrate must decrease.
    • Second- as some of this dust must wash out into the oceans over time I suppose the ocean is more cloudy than before (I can't say whether it would be more reflective or not - maybe?)

    From the above I wonder about life dependent on light near the surface.... And another affect - I wonder if the muds of the ocean bottom would show signs of these smaller dust particles being included - are mud slides easier with these additions?

    This is all in addition to the prior known, if debated, effects of global warming on the oceans (volume increases from heating to being added by melt water.) --Smkolins 18:46, 7 May 2006 (UTC)

    GD is (probably) mostly occurring over land (due to pollution being there). Further, light doesn't penetrate far into the oceans anyway. Also, the aerosol is largely soluble William M. Connolley 18:55, 7 May 2006 (UTC)
    This seems to be against several statements, for example the Global_dimming#Probable_causes section measures issues near Maldives - 435 miles south of India. Now the southern Islands weren't affected while the nothern ones were by this specific measurement. I presume the northern islands were affected by a airflow but that airflow hadn't evenly spread out around the Indian ocean basin air region. I wonder how far it reached? Africa?--Smkolins 20:12, 2 April 2007 (UTC)
    This is addressed in Relationship to hydrological cycle. Kgrr 16:39, 11 April 2007 (UTC)

    [edit] Nomination to GA failed

    Points to work on :

    • Section to be enlarged : Relationship to global warming.
    • Section to remove original research : Research.
    • The citations should follow the Cite.php formula or be in the Source section.
    • Some sections are too short.

    Lincher 14:12, 4 June 2006 (UTC)

    [edit] Enlarge relationship to global warming

    I am researching this and finding news articles. I will hope to uncover a few good Journal articles as well. For now, I am collecting the references in the external references section.Kgrr 15:36, 13 March 2007 (UTC)
    Still working on this section (see below)Kgrr 15:38, 24 March 2007 (UTC)

    [edit] Remove original research

    I have marked all unsubstantiated facts
    1. Note that the effect (2–3%, as above) is due to changes within the Earth's atmosphere; the value of the solar radiation at the top of the atmosphere has not changed by more than a fraction of this amount.[citation needed]
    2. The largest reductions are found in the northern hemisphere mid-latitudes [citation needed]
    3. This claim is not universally accepted and is very difficult to test.[citation needed]

    If no facts are found to substantiate these statements, they will be deleted in 7 days. Kgrr 21:21, 11 March 2007 (UTC)

    1. Independent research in Israel and the Netherlands in the late 1980s showed an apparent reduction in the amount of sunlight was fixed by SEWilco while I was working on it. I had deleted the reference because the URL was no longer vaid. Thanks!Kgrr 21:34, 11 March 2007 (UTC)

    All unsubstantiated facts have been either removed or backed with refereces. Kgrr 15:38, 24 March 2007 (UTC)

    [edit] Citations

    I have put the citations into proper form. Kgrr 21:21, 11 March 2007 (UTC)
    But there are still some things to do:
    1) Still need to take care of a double reference
    2) We probably should name all Journal references according to Harvard format
    Kgrr 15:40, 13 March 2007 (UTC)

    [edit] Some sections too short

    Which ones? Kgrr 15:36, 13 March 2007 (UTC)
    I've re-written most sections and added materials to all sections except one - relationship to Global Warmimg. (see below) Kgrr 15:38, 24 March 2007 (UTC)

    [edit] Checklist

    What is a good article?WP:WIAGA

    A good article has the following attributes. 1. It is well written. 2. It is factually accurate and verifiable. 3. It is broad in its coverage. 4. It follows the neutral point of view policy. 5. It is stable 6. It contains images, where possible, to illustrate the topic.

    All concerns have been addressed and it meets the checklist.Kgrr 16:29, 11 April 2007 (UTC)

    [edit] pan evaporation data as the most convincing evidence of global dimming ?

    k insists on adding:

    Scientists regard the pan evaporation data as the most convincing evidence of global dimming due to the simplicity and repeatability of the experiment.

    to this and the GW article. I don't believe it. As the article says:

    From the late 1980s onwards, scientists independently began working on solar radiation datasets and discovered declining trends worldwide

    ie, its radiation measurements that are evidence for dimming. The article continues:

    Atsumo Ohmura Secular variation of global radiation in Europe in 1989; Vivii Russak in 1990 "Trends of solar radiation, cloudiness and atmospheric transparency during recent decades in Estonia", and Beate Liepert in 1994 "Solar radiation in Germany - Observed trends and an assessment of their causes"

    Again: the evidence is *radiation* measurements. Against these scientific papers, k sets a Tv programme which doesn't cite any source for its claim.

    William M. Connolley 22:14, 10 March 2007 (UTC)

    My understanding is that the various researchers were causing confusion and consternation and it was the pan studies - which were far more world ranging, and relied on for so long, that convinced people it wasn't some temporary local phenomena or weird affect. Now finding a citation that says the pan studies were so important. So I agree with the stance, but it should be based on citation --Smkolins 03:24, 11 March 2007 (UTC)
    Well I dont agree with you; but if you can find some citations I might change my mind William M. Connolley 10:55, 11 March 2007 (UTC)
    It was mentioned in the BBC program, but that's just a TV program. So I have for now added the statement that the pan data corroborates the radiometer findings. As mentioned in the program, the pans don't have calibration problems and it's an easy experiment that anyone can repeat. Kgrr 16:29, 11 March 2007 (UTC)
    I have no problem with that. As Raymond A said, yes the data is simple but interpreting it isn't, since it depends on far more tahn just radiation. But that is another matter William M. Connolley 16:49, 11 March 2007 (UTC)

    Could you consider an interview of some of the notable authors that are cited in this piece? BBC program and transcript

    <quote>DR BEATE LIEPERT: My friends' reaction actually to Gerry's and to my work at the same time too was, oh my God this is really extreme, you are um contradicting global warming. Er do you know how many billions of dollars was spent on global warming research and you and this old guy er are contradicting er us.

    NARRATOR: So Liepert and Stanhill's work was widely dismissed. But Global Dimming was not the only phenomenon that didn't seem to fit with Global Warming. In Australia two more biologists, Michael Roderick and Graham Farquhar were intrigued by another paradoxical result - the world-wide decline in something called the pan evaporation rate.

    PROF GRAHAM FARQUHAR (Australian National University): It's called pan evaporation rate because it's evaporation rate from a pan. Every day all over the world people come out in the morning and see how much water they've got to add to a pan to bring it back to the level it was the same time the morning before. It's that simple.

    NARRATOR: In some places agricultural scientists have been performing this rather dull daily task for more than a hundred years. PROF GRAHAM FARQUHAR: The long-term measurements of pan evaporation are what gives it its real value.</quote>

    They are saying that they were not taken seriously on the radiometer data until the pan evaporation data was presented. Pan evaporation is taken as prima facie evidence of global dimming. The radiometer data was dismissed due to possible calibration errors.

    Ok .. a television interview of the experts is not good enough for you. Please remember NPOV before you respond with your OPINION Kgrr 22:19, 11 March 2007 (UTC)

    Sigh. You are doing your best to personalise this. Take out the narrators words and consider what the scientists are saying. B+L say nothing about PE. GF describes how to do it, and then says its valuable because it has long term records. Neither says its the best/prima-facie/whatever evidence for GD. (Note that if the evidence goes back 100y, why don't we have GD evidence back 100y from this stuff? Answer: because you can't turn PE into GD; you can only interpret the PE once you know about GD already) William M. Connolley 22:41, 11 March 2007 (UTC)
    Sighhhhhh You really argue for the sake of argueing, don't you? You never even read the initial link I gave. Do a Google Scholar search on "pan evaporation" and "global dimming". It's all over the literature. Both methods are seen as evidence of global dimming.
    Why is it that farmers would complain about needing less water for their fields? They never complained that it takes slightly less and less water, decade after decade. Scientists overlooked the source of data as they explain in both the BBC and NOVA pieces. It happens. But now that they have found the data, they see it as very reliable data to prove their hypothesis. There are loads of examples where scientists have a hypothesis and stumble over data that they themselved did not collect. Core samples are another example of this.
    Unfortunately, I think the BBC narrator sums it up pretty well:
    NARRATOR: It was the same with Europe and the USA. The drop in evaporation rate matched exactly the drop in sunlight reported by Beate Liepert and Gerry Stanhill. Two completely independent sets of observations had come to the same conclusion. Though it seemed incredible, there was no doubting Global Dimming now.
    Both pan evaporation and radiometry are prima facie evidence of global dimming. You just refuse to want to acknowledge this fact. Note that I never said that radiometry was not prima facie either. Kgrr 05:43, 12 March 2007 (UTC)
    I wonder if you even bother to read the text you insert. Why did you put it in? It doesn't prove your point, as I said above, and you haven't contested that William M. Connolley 09:32, 12 March 2007 (UTC)
    of course I do. YOU WIN - Since you believe that David Sington is just one of just a few isolated fools, let's just go with "BBC Horizon producer David Sington believes that many climate scientists regard the pan-evaporation data as the most convincing evidence of solar dimming."Kgrr 10:21, 12 March 2007 (UTC)
    I believe that television documentaries often have a tendency to use over-dramatic words. I don't see why you aren't happy to stick to the science. Find some nice published refs William M. Connolley 10:34, 12 March 2007 (UTC)
    I could not agree more. Some TV sources here in the US like Fox News are sources of disinformation. A tabloid would be a better source. Believe me, I'm working on it.Kgrr 13:17, 13 March 2007 (UTC)

    From the FAQ-

    Is there a possibility that the pan-evaporation method is too crude to be reliable? Rather the reverse. It is the very simplicity of the pan-evaporation experiments that makes them reliable and comparable between different locales and over long periods of time. That is why many climate scientists regard the pan-evaporation data as the most convincing evidence of solar dimming.

    [http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_qa.shtml Global Dimming

    Horizon producer David Sington answers questions about global dimming.] Science and Nature - TV & Radio Follow-up--Smkolins 21:01, 2 April 2007 (UTC)

    [edit] Irradiance and Insolation

    Are Irradiance and Insolation complete synonyms? There are two words, so what is the difference? Should the article refer to both, or just leave it as a See also? William, can you fill me in on this?? Kgrr 13:17, 13 March 2007 (UTC)

    Insolation (now commonly referred as irradation) differs from irradiance because of the inclusion of time. Insolation is the amount of solar energy received on a given area over time measured in kilowatt-hours per square meter (kwh/m2) Irradiance is the amount of solar energy received on a given area measured in kilowatts per square meter (kw/m2)[1].Kgrr 14:47, 14 March 2007 (UTC)

    [edit] New York Times / Common Dreams article

    Interesting summary on global dimming [2] My concern here is the reference. It's readable to everyone through Common Dreams, a progressive news agency, but one needs to register to see it on the New York Times site. Kgrr 13:27, 13 March 2007 (UTC)

    This did not appear to be an issue.Kgrr 16:26, 11 April 2007 (UTC)

    [edit] Global dimming and Solar dimming

    It appears that some people also call it solar dimming.[3]

    The article is pretty interesting and has more material for the relationship between global warming and global dimming. It looks like by exporting manufacturing to China and India, Europe and the US has been cleaning up its skies and making global warming worse by removing the blanket of pollution. And of course, global is probably getting worse in India and China as they have little or no environmental regulations.

    Also, should there be a section on the data deficit brought up in this reference?

    Should Solar dimming be re-directed to Global dimming? Kgrr 13:44, 13 March 2007 (UTC)

    Solar dimming requires the Sun to dim. Global dimming only requires that less sunlight reach the surface, and there are several possible reasons for that. Not all cases of dimming on the surface are due to dimming of the Sun. (SEWilco 06:40, 14 March 2007 (UTC))
    Currently Solar dimming is redirected to Global dimming. People in the past have used Solar dimming as a synonym with Global dimming. But since satellites have verified that it's not the sun that is changing, but the atmosphere, it appears that Global dimming is the culprit. Is Solar constant the correct article? Kgrr 16:34, 11 April 2007 (UTC)

    [edit] Probable causes

    We pretty much know the root cause seems to be pollution/aerosols/particulate. We should probably find a picture of a smokestack to move up towards the top. The contrails picture should be towards the bottom since that effect is only secondary.Kgrr 16:25, 15 March 2007 (UTC)

    The article should get to the point with an image like this one.
    A comparison of Beijing air on a day after rain and a sunny but smoggy day
    A comparison of Beijing air on a day after rain and a sunny but smoggy day
    —The preceding unsigned comment was added by Kgrr 19:11, 15 March 2007 (UTC)
    Sounds good. The pic is a teensy bit over-dramatic, though it would do William M. Connolley 19:29, 15 March 2007 (UTC)

    The article lacks the explanation that the water droplets are condensing o­n particulates. As a result, there is an increased amount of reflection of solar radiation back into space, leaving less light to reach the earth. This section still needs to be expandedKgrr 21:01, 19 March 2007 (UTC)

    Included the new picture of the Golden Gate with the brown cloud in the background. I think it serves the purpose. Expanded the section to include the thoughts on what the root cause is.Kgrr 16:24, 11 April 2007 (UTC)

    [edit] Early Reports

    I would like to propose a change in the Research section. Budyko's work attracted interest, but was overlooked because they thought that clouds would blanket the earth and warm it. It's only later in the 1990's when the Global warming / Global dimming paradox was discovered.

    From: The Wikipedia article states: "Early reports of "global dimming" attracted little interest, perhaps because the term itself had not yet been coined.[citation needed] The earliest reports seem to be by M. Budyko: "The effect of solar radiation variations on the climate of the Earth" in 1969, published in Tellus.[1]"

    To: One of the early reports to quantify the effects on clouds on the earth's radiation budget is described in a Technical Report by London [London 1957]. He found that clouds have a net cooling effect on the climate system. Mikhail Budyko worked with simple two-dimensional energy-balance climate models to investigate the reflectivity of ice [Budyko 1969]. He found that the ice-albedo feedback created a positive feedback loop in the Earth's climate system. The more snow and ice, the more solar radiation is reflected back into space and hence the colder Earth grows and the more it snows. Other studies confirmed that pollution or a volcano eruption could snap us into an ice age. [Rasool and Schneider (1971)][Lockwood (1979)]


    London, J. (1957) A study of the atmospheric heat balance. Final report AFC-TR-57-287 OTSPB129551 99pp, College of Engineering, New York University.

    Rasool, S. Ichtiaque, and Stephen H. Schneider (1971). "Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate." Science 173: 138-141.

    Lockwood, John G. (1979). Causes of Climate. New York: John Wiley., p. 162.

    Comments?Kgrr 17:50, 17 March 2007 (UTC)

    [edit] The Paradox

    I would like to propose another change in the Research section. The Paradox between the sunlight dimming and yet the ground temperatures rising is not adequately described in this article. Atsumu Ohmura is pretty much the one that discovered Global dimming.

    From: From the late 1980s onwards, scientists independently began working on solar radiation datasets and discovered declining trends worldwide; Atsumo Ohmura Secular variation of global radiation in Europe in 1989[5]; Vivii Russak in 1990 "Trends of solar radiation, cloudiness and atmospheric transparency during recent decades in Estonia"[6], and Beate Liepert in 1994 "Solar radiation in Germany - Observed trends and an assessment of their causes"[7]. Dimming has been observed in sites all over the Former Soviet Union [8]. Gerry Stanhill who studied these declines worldwide in many papers (see references) coined the term "dimming"[9].

    To: In the mid-1980's Atsumu Ohmura, a geography researcher at the Swiss Federal Institute of Technology, found something that left him in a shock. He found that solar radiation striking the Earth's surface had declined by more than 10% over the three previous decades. His findings are in apparent contradiction to global warming - the global temperature has steadily been going up. Less light reaching the earth would mean that it would have to cool as London had predicted. Atsumu Ohmura published his findings "Secular variation of global radiation in Europe" in 1989[5]. This was soon followed by others. Vivii Russak in 1990 "Trends of solar radiation, cloudiness and atmospheric transparency during recent decades in Estonia"[6], and Beate Liepert in 1994 "Solar radiation in Germany - Observed trends and an assessment of their causes"[7]. Dimming has also been observed in sites all over the Former Soviet Union [8]. Gerry Stanhill who studied these declines worldwide in many papers (see references) coined the term "Global dimming"[9].

    This should leave the reader with a couple of questions 1) Why is the ground getting hotter when it's getting less sunlight? 2) What happened to energy from the sun? Is it warming the upper atmosphere, or getting reflected? Instead of presenting a bunch of facts, we need to urge the reader to read on.

    Comments?Kgrr 20:00, 19 March 2007 (UTC)

    Where does "as London had predicted" come from? There is only one mention of London in the article and thats not relevant to this point (in fact its not clear why L is in there at all) William M. Connolley 21:08, 19 March 2007 (UTC)
    Ok Should I remove the reference to London altogether, or change it to Budyko's climate model? Kgrr 22:58, 19 March 2007 (UTC)
    I don't think you need a ref for "if there is less light it will cool down" William M. Connolley 09:42, 20 March 2007 (UTC)
    I will go without it then and integrate this new paragraph. Except how the Bay Bridge picture lays across the text, I'm starting to like the article. Considering the Global warming article defers the relationship with Global dimming to the Global dimming article, we should probably bolster that section too. After that, we should consider re-submitting soon in time for Earth Day Kgrr 14:55, 20 March 2007 (UTC)

    [edit] Global Warming May Have Accelerated

    A new NASA study has found that an important counter-balance to the warming of our planet by greenhouse gases – sunlight blocked by dust, pollution and other aerosol particles – appears to have lost ground.

    The graph shows the reversal of the trend

    Image:Aerosol dimming.jpg

    Is this latest study something we want to include in the Recent reversal of the trend section? Does this graph also prompt a section or material on aerosols from volcanoes? Kgrr 15:06, 21 March 2007 (UTC)

    [edit] Relationship to Hydrological Cycle

    Do we need a section relating Global dimming to the hydrological cycle? Or should this get included in the Effects on rainfall pattern section?

    Pollution produced by humans may be seriously weakening the Earth's water cycle - reducing rainfall and threatening fresh water supplies. A new study by researchers at the Scripps Institution of Oceanography suggests that tiny particles of soot and other pollutants are having a far greater effect on the planet's hydrological cycle than previously realized.Cat Lazaroff (2007-12-07). Aerosol Pollution Could Drain Earth's Water Cycle. "Through INDOEX we found that aerosols are cutting down sunlight going into the ocean," added Ramanathan. "The energy for the hydrological cycle comes from sunlight. As sunlight heats the ocean, water escapes into the atmosphere and falls out as rain. So as aerosols cut down sunlight by large amounts, they may be spinning down the hydrological cycle of the planet."

    In the new "Science" article, Ramanathan, Crutzen, J.T. Kiehl of the National Center for Atmospheric Research, and Rosenfeld of the Hebrew University of Jerusalem, say the aerosol issues raised by INDOEX are a "major environmental concern." I need to find this reference.

    I hope to find some more material for this section that must be added.Kgrr 14:42, 21 March 2007 (UTC)

    [edit] Relationship to global warming

    We really need to add more information into this one section. The Global warming article defers answering this relationship to Global dimming and here is the grand total of what explains the relationship:

       Further information: Global warming

    Some scientists now consider that the effects of global dimming have masked the effect of global warming to some extent and that resolving global dimming may therefore lead to increases in predictions of future temperature rise.[15]

    I will propose a paragraph or two. Kgrr 14:43, 21 March 2007 (UTC)

    Notes:

    In a paper published March 8 in the American Geophysical Union's Geophysical Research Letters, a research team led by Anastasia Romanou of Columbia University's Department of Applied Physics and Mathematics, New York, also showed that the apparently opposing forces of global warming and global dimming can occur at the same time.Kgrr 14:53, 21 March 2007 (UTC)

    Jacobson, M. Z.: Control of fossil-fuel particulate black carbon and organic matter, possibly the most efective method of slowing global warming, J. Geophys. Res., 107, doi:10.1029/2001JD001 376, 2002. http://www.stanford.edu/group/efmh/fossil/fossil.pdf Kgrr 02:22, 26 March 2007 (UTC)

    "Masking of Global Warming The surface dimming due to ABCs has a surface cooling effect, which should have masked some of the surface warming due to greenhouse gases. The magnitude of this masking effect is one of the central problems in climate change with significant implications for future climate changes and policy responses to global warming (Andreae et al., 2005). The extent of global warming is not fully reflected in the Earth’s observed surface temperatures. The additional heat trapped by the increase in greenhouse gases from the late nineteenth century to the present time should have committed the planet to a global warming in the range of 1ºC to 3ºC (see Ramanathan, 1988 for an explanation of the term committed warming). The observed global surface warming is only about 0.6 K, i.e., only about 20% to 60% of the committed warming (depending on whether we use 3 K or 1 K for the committed warming). Some of this warming has been masked by the dimming due to brown clouds and the remaining heat is stored in the depths of the ocean to be released in the coming decades to centuries. Through the process of convective overturning, oceans transfer infrared energy to their deepest layers and hold the heat, delaying the impact of global warming. Whether this stored heat will warm the atmosphere in a few decades or a few centuries is unknown. Current estimates of the ABC masking effect range from 30% to as high as 75% (Crutzen and Ramanathan, 2003; also see Andreae et al. in this issue for a more detailed consideration of the aerosols’ masking effect). The fundamental issue with this large range of uncertainty of the masking effect is that, policies to reduce ABCs (due to their effects on health, acid rain and agriculture) will unmask the cooling effect of ABCs quickly and have a potentially large effect in the acceleration of global warming. This is because the lifetime of ABCs is a few weeks and hence their masking effect will diminish as soon as their emissions are curtailed, whereas GHGs will respond to emission reduction policies on decadal to century time scales. Without a better quantification of the masking effect of ABCs, we would not know whether warming in the coming decades (if it were to occur) is due to the unmasking effect of ABCs (by efforts of cleaning up in Asia for example), or due to release of stored greenhouse heating in the oceans, or continued increase in emission of greenhouse gases. In the meantime, every decade we delay in taking action, we are committing the planet to additional warming that future generations have to deal with." V. Ramanathan http://www-ramanathan.ucsd.edu/PASScriptaVaria106.pdf Ramanathan, V., 2006: “Atmospheric Brown Clouds: Health, Climate and Agriculture Impacts” in the Pontifical Academy of Sciences Scripta Varia 106 Interactions Between Global Change and Human Health, (Pontifica Academia Scientiarvm 2006), pp. 47-60. Kgrr 03:01, 28 March 2007 (UTC)

    "But perhaps the most alarming aspect of global dimming is that it may have led scientists to underestimate the true power of the greenhouse effect.

    They know how much extra energy is being trapped in the Earth's atmosphere by the extra carbon dioxide we have placed there.

    What has been surprising is that this extra energy has so far resulted in a temperature rise of just 0.6 degree Celsius.

    This has led many scientists to conclude that the present-day climate is less sensitive to the effects of carbon dioxide than it was, say, during the ice age, when a similar rise in CO2 led to a temperature rise of six degrees Celsius.

    But it now appears the warming from greenhouse gases has been offset by a strong cooling effect from dimming - in effect two of our pollutants have been cancelling each other out.

    This means that the climate may in fact be more sensitive to the greenhouse effect than previously thought.

    If so, then this is bad news, according to Dr Peter Cox, one of the world's leading climate modellers.

    As things stand, CO2 levels are projected to rise strongly over coming decades, whereas there are encouraging signs that particle pollution is at last being brought under control.

    "We're going to be in a situation unless we act where the cooling pollutant is dropping off while the warming pollutant is going up.

    "That means we'll get reducing cooling and increased heating at the same time and that's a problem for us," says Dr Cox.

    Even the most pessimistic forecasts of global warming may now have to be drastically revised upwards.

    That means a temperature rise of 10 degrees Celsius by 2100 could be on the cards, giving the UK a climate like that of North Africa, and rendering many parts of the world uninhabitable.

    That is unless we act urgently to curb our emissions of greenhouse gases."

    http://news.bbc.co.uk/2/hi/science/nature/4171591.stm David Sington, BBC News "Why the Sun seems to be 'dimming'" Thursday, 13 January 2005

    Kgrr 05:18, 2 April 2007 (UTC)

    "Could Reducing Global Dimming Mean a Hotter, Dryer World?

    Despite concerns over global warming, scientists have discovered something that may have actually limited the impact of greenhouse gases in the atmosphere in recent years by reducing the amount of sunlight reaching the surface of the Earth.

    In research they published last year in the journal Geophysical Research Letters, a team led by Beate Liepert at the Lamont-Doherty Earth Observatory reported that they found a measurable decline between 1950 and 1990 in the amount of sun reaching the Earth's surface. The team concluded that solar radiation is being reduced by growing quantities of man-made particles in the atmosphere—in particular those produced by burning fossil fuels. This increase in small particles of ash, soot and sulfates has also caused the cloud cover to thicken in recent decades, further reducing solar irradiance. Only recently have climate models begun to include them in predictions of future global warming.

    (Global dimming was the subject of a recent special on the PBS science series NOVA featuring Beate Liepert.)

    "Aerosols are highly variable in space and time, which is why aerosol forcing of climate is generally very difficult to include in climate studies," said Liepert. "Furthermore, aerosols are found near the Earth's surface and affect mainly the fluxes of energy and water at the surface. These new ideas on the affects of aerosols might open up many avenues and solve more discrepancies in the climate change debate."

    It is widely agreed that greenhouse gasses in the atmosphere are causing temperatures to rise around the world. What has not been considered until recently is how temperatures would respond if the aerosol layer and cloud cover were not reflecting some of the suns radiation away from the planet. Liepert and her co-authors also concluded that the imbalance between a decline in solar radiation and warming surface temperatures will lead to weaker turbulent heat fluxes and reduced evaporation and precipitation, which could ultimately lead to a more humid atmosphere in which it rains less.

    Although rising temperatures should increase the amount of moisture in the atmosphere, the research shows that human-produced airborne aerosols can cause water to condense to form more, but smaller, cloud droplets. This process is likely contributing to the observed thickening of the Earth's cloud cover. However, smaller droplets are not heavy enough to sink through the air as rain. As a result, the cloud cover lasts longer and there is less rain.

    "Water has a characteristic residence time in the atmosphere before it gets rained out. In a warmer world, this residence time is longer because a warmer atmosphere can hold more water," said Liepert. "Aerosols affect clouds by suppressing rain and increasing its residence time."

    Examples of data supporting this new hypothesis include studies indicating a steady decline of water evaporation in the Northern Hemisphere over the past 50 years. Over the last 60 years, large regions of Eurasia have seen soil moisture increase by more than one centimeter per decade, yet no significant changes in precipitation are being seen. Global dimming also resulted in an observable difference in the brightness of sunlight. Even in remote areas, the atmosphere was more polluted and therefore darker. In the end, successful efforts to reduce emissions and clean up air pollution around the world could cause the full effect of global warming to become more noticeable in the near future.

    "We thought we live in a global warming world, but this is actually not right," Liepert said in a BBC interview last year. "We lived in a global warming plus a global dimming world and now we are taking out global dimming. So we end up with the global warming world, which will be much worse than we thought it will be, much hotter." "

    Could Reducing Global Dimming Mean a Hotter, Dryer World? Earth Institute News

    posted 04/14/06

    Contact: Ken Kostel 212-854-9729 or kkostel@ei.columbia.edu

    Contact: Clare Oh 212-854-5479 or coh@ei.columbia.edu http://www.earthinstitute.columbia.edu/news/2006/story04-14-06.php

    Kgrr 05:45, 2 April 2007 (UTC)

    The "relation to GW" should be dealt with here rather than in GW, cos thts too big already. Note that what this article doesn't really explain very well at the moment is that although direct radiation decreased by 4%-ish, the actual energy into the climate system didn't by anything like that, or we'd have seen massive cooling. So although GD has masked GW somewhat, it hasn't stopped it, and there has been a fairly fine balance William M. Connolley 08:27, 2 April 2007 (UTC)

    [edit] Review by Michael Roderick

    Hi Konrad

    I had a look at the article. It reads quite well and the links at the end should allow people to follow it up.

    A few suggestions.

    (1) In the research section, 5 lines down. "Other studies confirmed that pollution...". How about, speculated instead of confirmed.


    (2) Last para. in Research section where you list the numbers. Note that these numbers are for the terrestrial surface and not really a global average. Whether dimming (or brightening) occurred over the ocean has been a bit of an unknown.

    (3) Typo on the second last line of Pan Evaporation Section. i.e. "fills in the gaps in the paps in the data."

    (4) Recent Reversal of the Trend. I did not understand the first para. I agree that Wild et al. claimed brightening since 1990. They did this using measurements over land. The method used in Pinker et al. 2005 gives continued (but small) dimming over land and brightening over the ocean. Hence, over the land surface, Wild et al and Pinker et al disagree. There is as yet no resolution of this that I am aware of. It is a matter of intense research.

    I agree with this comment, in the context of an overall thumbs u as regards the informativeness of the article without it assuming some "pro/con" stance on the information contained therein. In particular, the graphic provided regarding the Pinker data is in direct contradiction to the (verbal) claims of Wild et al.Chas zzz brown 02:39, 25 March 2007 (UTC)


    Some questions.

    You may not believe it but this is the first time I have ever looked at Wikipedia. How does it work? Did they commission you to write the article or did you decide to contribute?

    Best wishes

    Michael Roderick Kgrr 15:52, 24 March 2007 (UTC)

    Point (4) seems to be correct. I don't have access to Science now, but the RC post agrees. I've rewritten this bit since (a) it read like Pinker had reconfirmed but Wild had; I've added the P/W diff William M. Connolley 16:08, 24 March 2007 (UTC)

    [edit] Relation to Health

    • Respiratory ailments
    • Carbon black
    • Acid rain

    ATMOSPHERIC BROWN CLOUDS: HEALTH, CLIMATE AND AGRICULTURE IMPACTS VEERABHADRAN RAMANATHAN http://www-ramanathan.ucsd.edu/PASScriptaVaria106.pdf Ramanathan, V., 2006: “Atmospheric Brown Clouds: Health, Climate and Agriculture Impacts” in the Pontifical Academy of Sciences Scripta Varia 106 Interactions Between Global Change and Human Health, (Pontifica Academia Scientiarvm 2006), pp. 47-60.

    Kgrr 03:00, 28 March 2007 (UTC)

    I included this in the section Global dimming as mitigation of global warming. Any more than this needs to be addressed in Climate change Kgrr 16:19, 11 April 2007 (UTC)

    [edit] Relation to Agriculture

    • Acid rain -> Reduced crop yeilds
    • Reduction of photosynthesis -> Reduced crop yeilds
    • Droughts, floods, violent weather

    ATMOSPHERIC BROWN CLOUDS: HEALTH, CLIMATE AND AGRICULTURE IMPACTS VEERABHADRAN RAMANATHAN http://www-ramanathan.ucsd.edu/PASScriptaVaria106.pdf

    "They estimate that the dimming effect of ABCs has reduced rice yield by 6–17% in India" http://intl.pnas.org/cgi/content/full/103/52/19668

    Kgrr 14:50, 26 March 2007 (UTC)

    I included this in the section Global dimming as mitigation of global warming. Any more than this needs to be addressed in Climate change Kgrr 16:18, 11 April 2007 (UTC)

    [edit] Atmospheric Brown Cloud

    "Quick facts

       * brown haze extends over South, Southeast and East Asia
   * haze is concentrated 3 kilometers above the surface and can travel halfway around the globe in less than a week
   * large surface cooling due to reduced sunlight perturbs the hydrological cycle

    Brown haze composition

       * black carbon and ash
   * sulfates
   * nitrates
   * mineral dust
   * 75% of the cloud is man-made

    Cause

       * forest fires
   * inefficient cooking fuels
   * factories
   * motor vehicle use

    Effects

       * significant reduction of solar radiation to the surface by as much as 15%
   * altered regional monsoon patterns (less sea evaporation from sunlight means less rain)
   * less rain in northwest India, Pakistan, Afganistan, and western PRC by as much as 40%
   * more rain and flooding in other areas
   * reduction of photosythesis (drop in agricultural productivity)
   * acid deposition and plant damage
   * respiratory ailments

    " http://www.adb.org/Vehicle-Emissions/general/environment-cloud.asp

    Global dimming or new article? I vote for here for now. I have created the redirection.

    Kgrr 14:47, 26 March 2007 (UTC)

    Extensive air pollution over Asia has drawn considerable attention from the global atmospheric science community. In India, as in other Asian countries, the government as well as scientists are wary of motivated criticism, but still have much to do to put the environment in order.

    India Together: Brown cloud or brown man

    Darryl D'Monte 22 Mar 2007

    http://www.indiatogether.org/2007/mar/env-browncld.htm

    Kgrr 14:32, 2 April 2007 (UTC)

    The Atmospheric Brown Cloud (ABC) or the Asian Brown Cloud — as it was known earlier — controversy is once again in the news with the Nobel Laureate, Paul Crutzen, and his team of scientists all set to establish two monitoring stations at the Maldives and North Korea to study the `ABC phenomenon'. The two centres will measure the levels and ascertain the exact cause of aerosol and carbon in the atmosphere in the Asian region. They will be set up by October this year.

    Aarti Dhar `Large Asian nations increasing air pollution' The Hindu FEB. 6 http://www.hindu.com/2004/02/07/stories/2004020702771200.htm

    Kgrr 14:36, 2 April 2007 (UTC)

    [edit] confused by language

    several places it refers to the amount of dimming but it seems to me to be inconsistent in how - and implying widely different values.... "of the order of a 4% reduction over the three decades from 1960–1990", "declined by more than 10% over the three previous decades", "average estimated at around 2–3% per decade", 5.3% (9 W/m²); over 1958–85 (Stanhill and Moreshet, 1992), 2%/decade over 1964–93 (Gilgen et al, 1998), 2.7%/decade (total 20 W/m²); up to 2000 (Stanhill and Cohen, 2001), 4% over 1961–90 (Liepert 2002)[13][14]" - mainly there are two forms reported - x% "over" decades, and x% "per" decade. Those two seem widely different to me - if I hear something changed over some decades I hear it took those decades to cover that stated change, not that it changed that amount each decade. Am I the only one? Can we adjust the phrasing or is it being driven by the sources? Or has this been some kind of huge issue trying to figure out what's going on? I mean a 4% change is a hugely different value than 75% change if they are to be over the same period of time.--Smkolins 20:04, 2 April 2007 (UTC)

    The phrasing of the findings is driven by the way the journal articles present their findings. It would be nice if they all reported the same units over the same time period. I imagine the difficulty of saying something is significant if the change is only 0.2% per year. So, the scientists express the results in x% per decade or x% over the course of their study. Even if all the data were normalized to say x% der decade, which dates covered and where the samples were taken makes these studies even more difficult to compare. Kgrr 17:33, 5 April 2007 (UTC)

    [edit] good article approval

    I read through the article twice and I was impressed by the article's depth and breadth. It passes all the good article criteria. It was very well written, neutral, well-sourced, pictures do illustrate the topic, and seems to be fairly stable as of this moment. Congratulations. Cronholm144 23:17, 12 April 2007 (UTC)

    [edit] Past tense?

    Recent edits (in particular this edit and this one) have changed the introduction to imply that global dimming is completely a thing of the past. But is it truly a thing of the past or is it merely somewhat less pronounced than it was previously? (My understanding is that although there is a reversal in progress, the earth's surface still gets less solar energy now than it did previously-- say, before the industrial revolution. So I would argue that global dimming should still be referred to in the present tense.)

    To clear up this confusion, someone more knowledgeable than I needs to present evidence to answer the following two questions. (1) Has the amount of solar energy reaching the earth returned to the levels of past millenia? (2) Does the word "dimming" in global dimming mean "it continues to get dimmer" or does it instead mean "it's dimmer than it was". (Since I do not have full access to the journal articles cited, I cannot easily research this on my own.) Riick 06:46, 29 April 2007 (UTC)

    Measurements do not exist from former time to fully answer that. Dimming - as in getting dimmer - is definitely over. Brightening - as in getting brighter, at least in direct radiation - is in progress. I don't know about absolute values though William M. Connolley 09:54, 29 April 2007 (UTC)

    [edit] Caption to the Golden Gate bridge picture

    I made this edit changing the caption of the picture from "Golden Gate Bridge with California's characteristic brown cloud in the background -- the most likely cause of global dimming." to "Golden Gate Bridge with California's characteristic brown cloud in the background -- a likely contributor to global dimming."

    Since then, User:Kgrr left the following message on my Talk Page:

    Your edit: the most likely cause of global dimming. -> a likely contributor to global dimming.
    The primary cause of Global Dimming IS thought to be global brown clouds - moreso now in places like China and India. Did you read the papers? Perhaps you can re-word your edit. Kgrr 13:24, 15 May 2007 (UTC)

    So... one of my concerns with the caption is that the poor juxtaposition of phrases suggests that "California's characteristic brown cloud" is the most likely cause of global dimming. That is assuredly not what is meant. I believe that Kgrr intends the caption to say that "brown clouds are the most likely cause of global dimming". If that assertion is true, we should rephrase the caption to make that clear. Something like "A picture of California's characteristic brown cloud. Brown clouds are thought to be the most likely cause of global dimming."

    However, I am not convinced that low-lying brown clouds like the one in the image are the most likely cause of global dimming.

    First of all, I admit to being fairly ignorant of the subject matter and more than willing to be corrected if I am wrong. I will tell you what I understand from reading this article. I admit to not having read any of the references.

    The article states that aerosols, particularly black soot, are responsible for global dimming by reflecting sunlight back into space and by forming the nuclei of clouds which also reflect sunlight back into space. The article doesn't say "brown clouds". Now, it may be obvious to everybody else that "black soot = brown clouds" but it isn't obvious to me.

    I also note that the article says "Though black carbon, most of which is soot, is an extremely small component of air pollution at land surface levels, the phenomenon has a significant heating effect on the atmosphere at altitudes above two kilometers (6,562 feet)." I'm not sure what to make of this sentence. Global dimming asserts a cooling effect due to reduced sunlight. Are we saying that black carbon heats up the atmosphere above 2km altitude and thereby cools the atmosphere below 2km altitude?

    In any event, it's not clear that the brown clouds in the Golden Gate picture represent black carbon above 2km altitude. I am under the impression that the effect of aerosols on global dimming occurs at higher altitudes than the low-lying smog shown in the Golden Gate picture. My reasoning is that, by the time sunlight, reaches the lower altitudes, the energy is already in the atmosphere and it's too late to reflect it back into space. This is supported by the fact that jet contrails are generally left at high altitudes (30,000 to 40,000 feet). It is also supported by Budyko's proposal to burn "sulfur in the stratosphere" where presumably it would have a greater effect than in the lower atmosphere.

    Once again, I admit to being a naïf in this area so please correct any misconceptions or errors in reasoning.

    --Richard 15:40, 15 May 2007 (UTC)

    Richard,
    Recent research by Veerabhadran Ramanathan, Stith and Prather is suggesting that a large portion of the brown cloud we see on the west coast there is an "Atmospheric Brown Cloud" swept from the far east across the Pacific. It's essentially a mix of dust and pollution.David Perlman. "Flying lab to test Pacific skies for dust from Asia Researchers seeking to discover its effect on weather, global warming", San Francisco Chronicle, April 23, 2007.  UCAR News Releases. We in the US are in turn polluting Europe. And, Europe pollutes the Far East."Scientist Says 'Asian Brown Cloud' Threatens Gulf". 
    China and India are major contributor to the brown clouds of smog — mostly black carbon, organic carbon and other aerosols such as sulphates and nitrates — formed by wildfires and by burning fossil fuels and biofuels.Box1. Brown clouds cast a dark shadow.
    The brown cloud NASA Eyes Effects of a Giant 'Brown Cloud' Worldwide. routinely climbs high enough into the atmosphere to hitch a ride on the fast-moving jet stream heading east to North America. In April and May, when seasonal winds are strongest, the high-altitude pollution can cross the Pacific in as little as four days. Since it's being carried by the jet stream, it's as high as 10km.
    From the ground, it looks just like the brown cloud you see over San Francisco. The picture is deceiving. Look how high it is above the ridge behind Berkely. You are looking at an aggregate for about 20-25 miles. The smog you see in the picture reaches 10-15,000 feet. I fly from Seattle to SFO regularly.
    I guess you need to see a space shuttle launch before you can appreciate how thin our atmosphere really is. When I lived in Boca Raton, FL, we used to watch space shuttle launches. At first it really surprised me as to how low an 80 mile orbit looks from the ground.
    Perhaps the pictures caption and the connection between global dimming and atmospheric brown clouds should be made clearer. Kgrr 14:37, 17 May 2007 (UTC)

    [edit] Edward Teller's Work

    It would also be worth mentioning Edward Teller's work, which can be found here:

    http://www.llnl.gov/global-warm/

    Teller's new idea seems to be the use of metallic resonant scatterers, which are much more effective than soot or rock dust. He also suggested that a cloud of these particles could be placed at the interior Lagrange point of the Earth/Sun. DonPMitchell 01:17, 15 November 2007 (UTC)

    This would fit under geoengineering William M. Connolley 09:26, 15 November 2007 (UTC)

    [edit] GA Sweeps Review: On Hold

    As part of the WikiProject Good Articles, we're doing sweeps to go over all of the current GAs and see if they still meet the GA criteria. I'm specifically going over all of the "Meteorology and atmospheric sciences" articles. I believe the article currently meets the majority of the criteria and should remain listed as a Good article. However, in reviewing the article, I have found there are some issues that need to be addressed. I have made minor corrections and have included several points below that need to be addressed for the article to remain a GA. Please address them within seven days and the article will maintain its GA status. If progress is being made and issues are addressed, the article will remain listed as a Good article. Otherwise, it may be delisted. If improved after it has been delisted, it may be nominated at WP:GAN. This article covers the topic well and if the above issues are addressed, I believe the article can remain a GA.

    Needs inline citations:

    1. "It is thought that global dimming was probably due to the increased presence of aerosol particles in the atmosphere caused by human action."
    2. "It is also thought that the water droplets in clouds coalesce around the particles."
    3. "Global dimming has interfered with the hydrological cycle by reducing evaporation and may have caused droughts in some areas"
      [I've replaced drought with "reduced rainfall" which is supported by the report in the hydro cycle section, so I think thats OK now William M. Connolley (talk) 21:46, 12 April 2008 (UTC)]

    Other issues:

    1. The lead needs to be expanded to two or three paragraphs to better summarize the article. See WP:LEAD for guidelines.
    2. "In essence, the sources of both greenhouse gases and air particulates must be addressed." This last sentence in the article does sound like a good idea, but it appears to be POV. It should either be reworded or removed completely for readers to make their own conclusions.

    I will leave the article on hold for seven days, but if progress is being made and an extension is needed, one may be given. I will leave messages on the talk pages of the main contributors to the article along with related WikiProjects so that the workload can be shared. If you have any questions, let me know on my talk page and I'll get back to you as soon as I can. Happy editing! --Nehrams2020 (talk) 05:46, 3 April 2008 (UTC)

    Progress so far
    Issue #1: "It is thought that global dimming was probably due to the increased presence of aerosol particles in the atmosphere caused by human action."
    Marked with Template:Fact tag for now. This can be easily supported with a reference. Kgrr (talk) 15:12, 3 April 2008 (UTC)
    William M. Connolley found a citation to support this. Kgrr (talk) 05:00, 10 April 2008 (UTC)
    Issue #2: "It is also thought that the water droplets in clouds coalesce around the particles."
    Found a quote to support.Kgrr (talk) 15:12, 3 April 2008 (UTC)
    Issue #3: "The lead needs to be expanded to two or three paragraphs to better summarize the article. See WP:LEAD for guidelines.
    "In essence, the sources of both greenhouse gases and air particulates must be addressed." This last sentence in the article does sound like a good idea, but it appears to be POV. It should either be reworded or removed completely for readers to make their own conclusions."
    I will take it on myself to add to the lede.Kgrr (talk) 15:12, 3 April 2008 (UTC)
    Issue #4: "In essence, the sources of both greenhouse gases and air particulates must be addressed." This last sentence in the article does sound like a good idea, but it appears to be POV. It should either be reworded or removed completely for readers to make their own conclusions."
    Moved text and reference in previous section to support this.Kgrr (talk) 15:12, 3 April 2008 (UTC)
    All GA Sweep issues resolved. Kgrr (talk) 05:00, 10 April 2008 (UTC)

    Anyone looking for references should read the IPCC AR4... specifically ch 3 and ch 7. And there is probably a lot of info there that we should import William M. Connolley (talk) 21:48, 3 April 2008 (UTC)

    I will. Thanks William. Kgrr (talk) 05:00, 10 April 2008 (UTC)
    Good job so far. The lead still needs to be expanded and the new inline citation needed request needs to be fixed. I'll continue to leave the article on hold for those two issues to be fixed. I struck through the ones that have already been corrected. If you have any questions, let me know on my talk page and I'll get back to you as soon as I can. --Nehrams2020 (talk) 01:42, 12 April 2008 (UTC)

    [edit] GA Sweeps Review: Pass

    Good job on addressing the above issues. I believe the article continues to meet the GA criteria and the article will keep its status. I would recommend continuing to add more information to the lead that has more information within the article. As it stands now, it is sufficient, but it could always improve. Continue to expand the article with any available information, ensuring that it is properly sourced and neutral. If you have any questions, let me know on my talk page and I'll get back to you as soon as I can. I have updated the article history to reflect this review. Keep up the good work and happy editing! --Nehrams2020 (talk) 06:51, 14 April 2008 (UTC)