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Airborne dust, water vapour and global warming

  1. Jun 10, 2008 #1
    More dust in the air presumably means that there are more nuclei on which water molecules can condense to form liquid water.Water vapour is a greenhouse gas so can the current trend in global warming be attributed to less dust in the air than usual resulting in more water vapour and higher temperatures? And why would there be less dust given that winds are getting stronger? Are the deserts becoming more sticky - have manmade chemicals glued desert particulates together making them heavier and more difficult for the wind to move? Or have the lightest sand particles been moved by the passage of millennia leaving only the heavier ones on the surface of the deserts? This wouldn't explain why the glacial-interglacial cycle exists however because we would expect a constant rise in average global temperature over the 1.5 million years that the cycle has existed, based on this theory. Australia has a large desert area.
    Does dust from Australia's deserts cause the cooler years in the south pacific between El Nino events?
     
    Last edited: Jun 10, 2008
  2. jcsd
  3. Jun 10, 2008 #2
    More dust in the air presumably means that there are more nuclei on which water molecules can condense to form liquid water.Water vapour is a greenhouse gas so can the current trend in global warming be attributed to less dust in the air than usual resulting in more water vapour and higher temperatures? And why would there be less dust given that winds are getting stronger? Are the deserts becoming more sticky - have manmade chemicals glued desert particulates together making them heavier and more difficult for the wind to move? Or have the lightest sand particles been moved by the passage of millennia leaving only the heavier ones on the surface of the deserts? This wouldn't explain why the glacial-interglacial cycle exists however because we would expect a constant rise in average global temperature over the 1.5 million years that the cycle has existed, based on this theory. Volcanoes can emit dust and so if they are a major contributor to liquid water formation - and cooling -then they are probably also emitting a fair amount of gases with the dust too.These gases could be heating the earth up but if they are doing this then wouldn't we expect the biggest temperature rises to be in the vicinity of volcanoes where the gases are concentrated the most (underwater or land based volcanoes) which does not seem to be the case.
    I think we have to conclude that since global warming has occurred in the past long before mankind's industrial age that
    global warming is being caused by an external agent such as the sun which has somehow adjusted its power output and heated the atmosphere in general.
     
  4. Jun 10, 2008 #3

    mgb_phys

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    I'm going to regret wading into a climate change debate - I know!

    The atmosphere isn't simple.
    Water vapour has an ir absorption spectra and traps heat - but cloudsreflect radiation and have a strong cooling effect. It all dependson heights and timescales.
    Temperatures havea bigger effect on when rain will form than nucleation sites. I don't think there is ever a lack of rain becuase of not enough dust.

    The overall level of dust may have gone up quite a bit in the last 2000 years as the sahara and gobi deserts expanded - thanks largely to goats. This has had a big effect on rainfall patterns in africa/middle east due to wind changes aroiund the hot desert but not due to the level of dust.
    New dust is constantly formed by erosion and fine dust is laid down in new rocks.

    As to volanoes - they do have a huge but relatively short term atmospheric effect. A volcano will put gas and volatiles into the stratosphere where they will go around the earth in a couple of days so there is little local effect around a volcano.
     
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