[astro] the physics arXiv blog

[Eugen Leitl]

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From: the physics arXiv blog <howdy at arxivblog.com>
Date: Tue, 29 Apr 2008 19:04:42 -0500 (CDT)
To: eugen at leitl.org
Subject: the physics arXiv blog
Reply-To: the physics arXiv blog <howdy at arxivblog.com>


[1]the physics arXiv blog

   [2]Solving the faint young Sun problem

   Posted: 29 Apr 2008 12:00 AM CDT

   [3]Faint young Sun problem 

   We know by studying ancient rocks that liquid water existed on the
   surface of Earth at least 3.7 billion years ago. That implies that the
   surface temperature at that time was at least 273K.

   We also know by studying stars similar to ours that the Sun must have
   been significantly less bright than it is now (Sol is thought to have
   increased in luminosity by 30 per cent since then). That ought to have
   resulted in temperatures on Earth that were well below freezing.

   This contradiction is known as the "faint young Sun" problem and
   nobody has adequately explained it.

   The most common explanation is that the planet must have been warmed
   by some kind of greenhouse gas effect mediated perhaps by carbon
   dioxide, atmospheric haze, ammonia or methane. The trouble is that the
   evidence indicates that these gases existred in quantities at least an
   order of magnitude too little to have done the job.

   So what gives? According to Philip von Paris of the Institute of
   Planetary Research  at the German Aerospace Centre in Berlin, Germany,
   und Freunds, the mix up is largely the result of an error in our
   understanding of how much radiation was absorbed in those days.  His
   team has used a new atmospheric model of the early Earth to determine
   that the required green house effect would have been possible with
   carbon dioxide with a partial pressure of about 2.9mb, about an order
   of magnitude less than previously thought.

   That's a pretty good match with the amount of carbon dioxide thought
   to have been around between 2 and 2.5 billion years ago. Nice result.
   But von Paris has been a little over ambitious. He says: "thus, the
   contradiction between sediment data
   and model results disappears," implying that the faint young Sun
   problem is solved.

   But hang on a minute, he seems to have forgotten the billion years or
   so between 2.5 and 3.7  billion years ago in which the temperature is
   still unexplained.

   Nice try, von Paris. But we're not that easily foooled.

   Ref: [4]arxiv.org/abs/0804.4134: Warming the early Earth - CO2
   reconsidered

   [5][arXivblog?i=ofSuQb] 
   [6][arXivblog?i=QGr4aG] [7][arXivblog?i=OSOeZG]
   [8][arXivblog?i=SABtPg] [9][arXivblog?i=NLxylG]
   [10][arXivblog?i=aSHXog] [11][arXivblog?i=XVt3HG]
   [12][arXivblog?i=LvAzGg] [13][arXivblog?i=6bRz2G] 
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References

   1. http://arxivblog.com/
   2. http://feeds.feedburner.com/~r/arXivblog/~3/279849761/
   3. http://arxivblog.com/wp-content/uploads/2008/04/faint-young-sun.jpg
   4. http://arxiv.org/abs/0804.4134
   5. http://feeds.feedburner.com/~a/arXivblog?a=ofSuQb
   6. http://feeds.feedburner.com/~f/arXivblog?a=QGr4aG
   7. http://feeds.feedburner.com/~f/arXivblog?a=OSOeZG
   8. http://feeds.feedburner.com/~f/arXivblog?a=SABtPg
   9. http://feeds.feedburner.com/~f/arXivblog?a=NLxylG
  10. http://feeds.feedburner.com/~f/arXivblog?a=aSHXog
  11. http://feeds.feedburner.com/~f/arXivblog?a=XVt3HG
  12. http://feeds.feedburner.com/~f/arXivblog?a=LvAzGg
  13. http://feeds.feedburner.com/~f/arXivblog?a=6bRz2G
  14. http://arxivblog.com/
  15. http://www.feedburner.com/fb/a/emailunsub?id=8632699&key=kesJ612ZsV
  16. http://feeds.feedburner.com/arXivblog
  17. http://feeds.feedburner.com/arXivblog

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-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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