[Vision2020] 350.org Science: Target Atmospheric CO2: Where Should Humanity Aim?

[Ted Moffett]

http://www.350.org/home
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http://www.giss.nasa.gov/research/briefs/hansen_13/
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http://arxiv.org/abs/0804.1126

Target atmospheric CO2: Where should humanity aim?
Authors: J. Hansen<http://arxiv.org/find/physics/1/au:+Hansen_J/0/1/0/all/0/1>(1
and 2), M.
Sato <http://arxiv.org/find/physics/1/au:+Sato_M/0/1/0/all/0/1> (1 and 2), P.
Kharecha <http://arxiv.org/find/physics/1/au:+Kharecha_P/0/1/0/all/0/1> (1
and 2), D. Beerling<http://arxiv.org/find/physics/1/au:+Beerling_D/0/1/0/all/0/1>(3),
R.
Berner <http://arxiv.org/find/physics/1/au:+Berner_R/0/1/0/all/0/1> (4), V.
Masson-Delmotte<http://arxiv.org/find/physics/1/au:+Masson_Delmotte_V/0/1/0/all/0/1>(5),
M.
Pagani <http://arxiv.org/find/physics/1/au:+Pagani_M/0/1/0/all/0/1> (4), M.
Raymo <http://arxiv.org/find/physics/1/au:+Raymo_M/0/1/0/all/0/1> (6), D. L.
Royer <http://arxiv.org/find/physics/1/au:+Royer_D/0/1/0/all/0/1> (7), J. C.
Zachos <http://arxiv.org/find/physics/1/au:+Zachos_J/0/1/0/all/0/1> (8) ((1)
NASA GISS, (2) Columbia Univ. Earth Institute, (3) Univ. Sheffield, (4) Yale
Univ., (5) LSCE/IPSL, (6) Boston Univ., (7) Wesleyan Univ., (8) Univ.
California Santa Cruz)
(Submitted on 7 Apr 2008 (v1 <http://arxiv.org/abs/0804.1126v1>), last
revised 15 Oct 2008 (this version, v3))

Abstract: Paleoclimate data show that climate sensitivity is ~3 deg-C for
doubled CO2, including only fast feedback processes. Equilibrium
sensitivity, including slower surface albedo feedbacks, is ~6 deg-C for
doubled CO2 for the range of climate states between glacial conditions and
ice-free Antarctica. Decreasing CO2 was the main cause of a cooling trend
that began 50 million years ago, large scale glaciation occurring when CO2
fell to 450 +/- 100 ppm, a level that will be exceeded within decades,
barring prompt policy changes. If humanity wishes to preserve a planet
similar to that on which civilization developed and to which life on Earth
is adapted, paleoclimate evidence and ongoing climate change suggest that
CO2 will need to be reduced from its current 385 ppm to at most 350 ppm. The
largest uncertainty in the target arises from possible changes of non-CO2
forcings. An initial 350 ppm CO2 target may be achievable by phasing out
coal use except where CO2 is captured and adopting agricultural and forestry
practices that sequester carbon. If the present overshoot of this target CO2
is not brief, there is a possibility of seeding irreversible catastrophic
effects.

  Comments: 20 pages, 7 figures; final version accepted by Open Atmospheric
Science Journal; supporting article separately submitted to arXiv as "Target
atmospheric CO2: Supporting material",
arxiv:0804.1135<http://arxiv.org/abs/0804.1135> Subjects:
Atmospheric and Oceanic Physics (physics.ao-ph) Journal reference: Open
Atmos. Sci. J. (2008), vol. 2, pp. 217-231 DOI:
10.2174/1874282300802010217<http://dx.doi.org/10%2E2174/1874282300802010217>
Cite as:
arXiv:0804.1126v3 <http://arxiv.org/abs/0804.1126v3> [physics.ao-ph]
 Submission historyFrom: James Hansen [view
email<http://arxiv.org/auth/show-email/32472f58/0804.1126>]

*[v1] <http://arxiv.org/abs/0804.1126v1>* Mon, 7 Apr 2008 20:16:55 GMT
(477kb)
*[v2] <http://arxiv.org/abs/0804.1126v2>* Wed, 18 Jun 2008 21:38:01 GMT
(454kb)
*[v3]* Wed, 15 Oct 2008 21:51:55 GMT (550kb)

Which authors of this paper are
endorsers?<http://arxiv.org/auth/show-endorsers/0804.1126>

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Vision2020 Post: Ted Moffett
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