Solar dimming, rapid drop in 3 decades

Discussion in 'Earth Science' started by Jagger, Jan 16, 2005.

  1. eburacum45 Valued Senior Member

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    1,297
    The fact remains that clear-sky radiation causes cooling, even during the day; I would like to trust that the cooling effect of a decrease in cloud cover would be taken into account in this situation.
    Increasing cloud cover increases albedo, and decreases the energy flux inwards,
    but
    increasing cloud cover decreases the clear-sky radiation and decreases the energy outwards.
    The two effects could cancel out, as the New Scientist article points out
    http://www.newscientist.com/article.ns?id=dn5048

     
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  3. Maddad Time is a Weighty Problem Registered Senior Member

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    Reflectance is of course albedo *Wondering how Andre will respond*
     
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  5. Andre Registered Senior Member

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    If I may borrow from Nilequeens link:

    Emphasize mine, to highlight that the author refrained from using understatements as "appears to", "may have", etc. It sounds likewise silly to state: "apparantly it seems that water may tend to boil at 100 degrees C". But I agree I was a bit overconfident (agitated) when I used the term "definite".

    Now if we compare that sequence with the global temperatures the last several years:

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    Taking in mind the several other influences on global temperature, the general trend does not seem to contradict the albedo changes too much.

    A clear increase in albedo the last few years? More clouds? Nett air polution decreasing, increasing Antarctic sea ice? I don't know but at least the global temperature of those years stabilized, not directly opposing the suggestion that albedo and temperature are linked.
     
    Last edited: Jan 22, 2005
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  7. Ophiolite Valued Senior Member

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    That was my primary objection. I have not even reached a provisional view on this, so will react to suggestions that any of the evidence is clear or definite in favour of either viewpoint.

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    Thanks NileQueen. I can access the weather link now.
     
    Last edited: Jan 22, 2005
  8. guthrie paradox generator Registered Senior Member

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    Dont know if your interested or anything, but heres a link to a climate change site discussing the Horizon global dimming program, and saying they got it a bit wrong:
    http://www.realclimate.org/index.php?p=105#more-105

    "The suggested 'doubling' of the rate of warming in the future compared to even the most extreme scenario developed by IPCC is thus highly exaggerated. Supposed consequences such as the drying up of the Amazon Basin, melting of Greenland, and a North African climate regime coming to the UK, are simply extrapolations built upon these exaggerations. Whether these conclusions are actually a fair summary of what the scientists quoted in the program wanted to say is unknown. However, while these extreme notions might make good television, they do a dis-service to the science."
     
  9. NileQueen Registered Senior Member

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    Maddad:Reflectance is of course albedo

    I am wondering how earthshine data compares to albedo data collected from some point out in space? Earthshine intensities would have to be collected from some point above our atmosphere. I'm not sure how they collect the data, or how the data compares.
     
  10. Andre Registered Senior Member

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    889
    An excellent link Guthrie, and:

    I would tend to say: "Which science?" Could you really call continuously unfounded scary ideas, not backed up by independent evidence in any way, still science?

    Anyway, from that link:

    Now check these pics I made last week in Eastern Europe and look at the color of the air just above the horizon.

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    would that be more light absorbing (hence dark) soot or light reflecting (hence bright) aerosols?

    Consequently, it may be that we have underestimated the warming effect of absorbing soot. Can we expend that hypothesis and find more evidence (following the scientific method)?
     
  11. Andre Registered Senior Member

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    889
    Now, perhaps I'm not the only one who think that the nett effect of all forms of haze and aerosols is absorption rather than reflection.

    http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=10811216&dopt=Abstract

     
  12. guthrie paradox generator Registered Senior Member

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    Slowing the hydrological cycle? Does that mean less rainfall in some parts of the world?
     
  13. Andre Registered Senior Member

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    889
    Yes, but that's his idea, just a hypothesis. Although Earth recieves less visible light due to the dimming effect of soot, it recieves more re-radiated IR (warmth) radiation from the same soot, this is likely to be causing what it known as "global warming".

    It may or may not have to do with the general Sea Surface Temperatures (SST) being higher than normal on the average:

    http://lwf.ncdc.noaa.gov/oa/climate/research/2004/dec/global.html#Temp

    But higher SST would facilitate evaporation and hence increase the pace in the hydrological cycle.
     
  14. eburacum45 Valued Senior Member

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    1,297
    I trust you realise that Ramanathan was the main authority cited in the BBC Horizon proramme; he was suggesting that the slow down in the hydrological cycle caused the devastating droughts in Africa.

    In any case, if the soot becomes a nucleus for a cloud droplet, that radically changes its effect on albedo and on radiated infrared; so a distinction must be made between increased cloud cover and smog. The number of factors involved in considerations like this make simplistic comments worthless- which is why the Horizon program was so annoying.
     
  15. Andre Registered Senior Member

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    889
    Yes, but I seem to remember that Ramanathan had nothing to do with the reflection hypothesis. He seemed only to be cited about the effect of haze/aerosols in the tropical areas and the concequences for the hydrolic cycle.
     
  16. kfs Registered Member

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    global dimming seems reasonable.

    look how temperatures shot up after 911 - when air transport was suspended - and europes rapid rise with europes anti-particulate measures.

    I read that it was like 30% level of dimming than 10% globally.

    What this means is that false global warming debate is over. you accept dimming, then dimming in face of a warming world means only one thing: CO2 has a far higher effect on keeping is warm than what we ever thought because the dimming reduces surface heating.

    The effect of the dimming isnt under contention since the science is simple and well understood apparantly.
     
  17. Andre Registered Senior Member

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    889
    Right the false global warming debate could be over. The combination of global diming and global decrease of reflectivity (which is happily ignored) indicates that more light is absorped, not that more light is reflected, then the earth reflectivity as measured on the dark side of the moon should have increased but again it decreased instead.

    So, now we know that something is increasingly absorpting light and is heating up the atmosphere. We know that CO2 does not affect visible light. So that can't be it. We do know that haze and soot do absorp visible light and the level of those has increased significantly, especially in the tropics.

    Consequently we should fight soot and haze but that's not the same as controlling emission.
     
  18. extrasense Registered Senior Member

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    exectly right.

    Commie stinkos are creating global climate changes by their stench.

    Deal with them. That's all.

    e

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    s
     
  19. Starthane Xyzth returns occasionally... Valued Senior Member

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    There must be a very subtle difference in the properties of fine particulates, if some simply cool the Earth by reflecting sunlight while others convert light into heat and thereby warm the Earth (despite apparently dimming the Sun!) Particle size is an obvious factor, but also surface color and perhaps electrostatic properties.

    From that point of view, different types of pollution could work against one another and keep the global temperature stable... in theory, although of course the warming effect of CO2 and methane etc. vastly outweighs any manmade cooling factor right now.
     
  20. echos_love Registered Member

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    please could you explane what globle dimming i have got a basic drif , what dose it mean for earth, and will it affect humans in futur(near)

    ~sorry for poor spelling~
     
  21. Starthane Xyzth returns occasionally... Valued Senior Member

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    1,465
    If you go back to the beginning of this thread, you'll see what it means - that the solar radiation flux reaching the Earth's surface has declined considerably in recent decades. That the Sun itself is fading seems doubtful, so the implication is that our atmosphere is becoming more absorbant - in other words, either cloudier or dirtier. But not cooler, of course.

    It certainly wouldn't be noticeable by the human eye, if the apparent brightness of direct sunlight declined by 50% or more: the Sun is far too luminous for our eyes to cope with, and would look just as dazzling even from the distance of Jupiter (you'd never get a tan out there, though...); and plants can still thrive on a much-reduced solar flux, as long as it isn't permanently overcast and really, visibly gloomy.
     
  22. Michael 歌舞伎 Valued Senior Member

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    Global Dimming

    4corners: Global Dimming
    BBC: Global Dimming
    Well this sucks. So in essence the earth is getting colder and warmer by the very same pollution source.

    CO2 is warming the Earth up while the soot is cooling the Earth down.

    I’m just waiting for this huge tsunami to flatter NY. . . .

    Anyway, with this Presidency and the mood in the US now-a-days I do not think much is going go be done about this. I mean just listening to fellow Americans bitch about gasoline prices (which is still ridiculously low when compared to anywhere else in the developed world) while driving along in a 8 ton pickup to the grocery market 500 meters up the road . . . .
     
  23. Ophiolite Valued Senior Member

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    9,232
    While many people love NY,
    I would be surprised if a tsunami would speak especially well of it.

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    Last edited by a moderator: Mar 23, 2005

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