Target Atmospheric CO2: Where Should Humanity Aim?
GSA Today, 2008 · paper · Earth science
Uses paleoclimate data to estimate climate sensitivity and to ask what atmospheric CO2 level humanity should aim for. It concludes CO2 must fall from 385 ppm to at most 350 ppm, likely less, to preserve a planet like today's.
Checked: PDF from arxiv.org, fetched 4 Oct 2026. Page numbers are those of that PDF.
3 findings
Reference or label Section 2.1 cites "sea level based on Red Sea sediment cores [18]", but [18] is Vimeux et al. (Vostok temperature, deuterium excess); the Fig. 1 caption on the same page cites "sea level [19]" and [19] is Siddall et al., "Sea-level fluctuations during the last glacial cycle".
- p. 3 Section 2.1, first paragraph
sea level based on Red Sea sediment cores [18]
- p. 3 Fig. 1 caption
level [19] for past
- p. 17 Reference [18]
Vimeux F, Cuffey KM, Jouzel J. New insights into Southern Hemisphere temperature changes from Vostok ice
- p. 3 Fig. 1 caption
CH4 [17] and sea level [19] for past 425 ky
Judge's note: Viewed page 3: the text reads 'cores [18]' and the caption 'sea level [19] for past 425 ky'. Reference list on pages 17-18: [18] is Vimeux, Cuffey, Jouzel on Southern Hemisphere temperature from Vostok; [19] is Siddall et al. on sea level. The text citation should be [19]. The same sentence also gives the gases as [17, 18] where the caption gives [17].
Second check: another model agreed
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Reference or label The observed curve in Fig. 1c is sourced to "Vostok temperature change [17] divided by two" in the text (page 4) but to "Antarctic temperature change [18] divided by two" in the Fig. 1 caption (page 3).
- p. 4 Section 2.1, paragraph beginning 'Multiplying the sum'
Vostok temperature change [17] divided by two (red
- p. 3 Fig. 1 caption, panel (c)
change [18]
- p. 3 Fig. 1 caption, panel (c)
temperature change [18] divided by two
- p. 4 Section 2.1, paragraph after Eq. 1
Vostok temperature change [17] divided by two
Only the authors can say what is right here.
Judge's note: Viewed pages 3 and 4. [17] is Petit et al. 1999 and [18] is Vimeux et al. 2002 (deuterium-excess corrected temperature); both concern Vostok temperature, so either could be the source, but the two places name different single sources for one curve. The Fig. 2 caption cites [17, 18]. Only the authors can say which record is plotted.
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Reference or label Reference [91] "Hasselmann K. Ocean circulation and climate change. Tellus B 2002; 43: 82-103." pairs volume 43 with year 2002, which does not fit the other Tellus B entries in the same list (vol. 48 = 1996 in [78], vol. 55 = 2003 in [83]); volume 43 would be 1991.
- p. 20 Reference [91]
Hasselmann K. Ocean circulation and climate change. Tellus B 2002; 43: 82-103.
- p. 20 Reference [91]
Tellus B 2002; 43: 82-103.
- p. 19 Reference [78]
Tellus B 1996; 48:
- p. 20 Reference [83]
Tellus B 2003; 55: 378-390.
Only the authors can say what is right here.
Judge's note: Viewed pp. 19 and 20. Within the reference list, [78] gives Tellus B 1996; 48 and [83] gives Tellus B 2003; 55, a one-volume-per-year sequence that puts volume 43 in 1991 and volume 54 in 2002. So the year and volume in [91] disagree on the list's own evidence. Which of the two is wrong (most likely the year, 1991) rests on outside knowledge of the Hasselmann paper and is for the authors to confirm.
Second check: another model agreed
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13 minor (typos and the like; most checked by the judge only)
Typo Inconsistent hyphenation: "Given additional warming ‘in-the-pipeline’" (page 13) against "‘in the pipeline’" on pages 2 and 11 and in the heading of Section 2.4.
- p. 13 Section 4.2, coral reefs paragraph
‘in-the-pipeline’
- p. 2 Introduction
‘in the pipeline’
Judge's note: Viewed the page 13 and page 2 crops and page 11. The hyphenated form appears once; elsewhere the phrase is unhyphenated. Cosmetic.
Second check: none (judge only)
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Typo Unclosed parenthesis: "(e.g., ice melts at both poles when the spin-axis tilt increases, and ice melts at one pole when perihelion, the closest approach to the sun, occurs in late spring [7]."
- p. 4 Section 2.2, third paragraph
(e.g., ice melts at both
- p. 4 Section 2.2, third paragraph
occurs in late spring [7]. Also a warming climate
- p. 4 Section 2.2, third paragraph
approach to the sun, occurs in late spring [7]. Also a warming climate
- p. 4 Section 2.2, third paragraph
(e.g., ice melts at both poles when the spin-axis tilt increases, and ice melts at one pole when perihelion, the closest approach to the sun, occurs in late spring [7].
Judge's note: Viewed page 4: the parenthesis opened before 'e.g.' in Section 2.2 is not closed; the sentence ends 'late spring [7].' and the next begins 'Also a warming climate'.
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Typo Missing full stop between sentences: "estimated earlier [7] Because N2O data are not available".
- p. 4 First line of page
estimated earlier [7] Because N2O data are not available
Judge's note: Viewed page 4, first line: a wide space but no period after '[7]' before 'Because'.
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Typo Heading "2.3 Time scales" lacks the period after the number that the other subsection headings carry ("2.1. Verification", "2.2. Slow feedbacks", "2.4. Warming ...").
- p. 5 Heading 2.3
2.3 Time scales
- p. 4 Heading 2.2
2.2. Slow feedbacks
Judge's note: Viewed the page 5 crop and page 4: '2.3 Time scales' has no period after 2.3, while 2.1., 2.2., 3.3., 4.1. and the others do. Cosmetic.
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Typo "We hinge our calculations at 35 My for several reasons. Between 65 and 35 My ago there was little ice on the planet ... Second, we want to estimate ... Finally, the relation": the list has 'Second' and 'Finally' but no 'First'.
- p. 9 Section 3.2
Between 65 and 35 My ago there
- p. 9 Section 3.2
Between 65 and 35 My ago there was little ice on the planet
Judge's note: Viewed the page 9 crop. The first reason is not marked 'First'. Stylistic only; the meaning is clear.
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Typo Inconsistent spelling: "could largely off-set reductions of high albedo aerosols" (page 12) against "tend to offset negative aerosol forcing" in the paragraph above and "offset by increasing CO2" (page 16).
- p. 12 Section 4.2
could largely off-set reductions
- p. 16 Section 4.5
offset by increasing CO2
Judge's note: Viewed the page 12 and page 16 crops. 'off-set' is hyphenated once; 'offset' is closed elsewhere, including five lines earlier on page 12. Both forms are accepted; cosmetic.
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Typo Reference [5]: "Hansen J, Sato M, Ruedy, et al." gives Ruedy without an initial; the same author is "Ruedy R" in references [8], [12], [14] and [20].
- p. 17 Reference [5]
Hansen J, Sato M, Ruedy, et al.
Judge's note: Viewed page 17: [5] reads 'Ruedy, et al.' with no initial, while [8], [12] and [14] on the same page read 'Ruedy R'.
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Typo Reference [16] title misspells the word as "terrestrial paeleoclimate data" (should be 'palaeoclimate' or 'paleoclimate').
- p. 17 Reference [16]
terrestrial paeleoclimate data
- p. 19 Reference [73]
Barnett TP, Adam JC, Lettenmaler DP.
Judge's note: Viewed the crop of p. 17: reference [16] prints 'paeleoclimate', which is neither the British nor the American spelling. The 'Lettenmaler' point also raised here is handled under C022.
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Typo Reference [42] prints the fourth author as "Langereis CG, Abeld HA, Dai S"; the author of the cited Nature 2007; 445: 635-638 paper is believed to be Abels HA.
- p. 18 Reference [42]
Langereis CG, Abeld HA, Dai S
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that the fourth author of Dupont-Nivet et al., Nature 2007; 445: 635-638 is H. A. Abels. The crop of p. 18 clearly prints 'Abeld HA', so this is not an extraction artefact, but the correct spelling cannot be verified from the files.
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Typo Reference [76] misspells the journal name: "Nautre 2008 (in press)" should read 'Nature'.
- p. 19 Reference [76]
Nautre 2008 (in press)
- p. 19 Reference [76]
Gleckler PJ, Wijffels, Barker PM, Dunn JR
Judge's note: Viewed p. 19 and a crop including [76]: 'Nautre' is printed. Reference [97] gives the journal as Nature. The missing initials for Wijffels, also raised here, are handled under C020.
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Typo Reference [76] omits one author's initials: "Gleckler PJ, Wijffels, Barker PM", whereas reference [97] prints "Wijffels SE".
- p. 19 Reference [76]
Gleckler PJ, Wijffels, Barker PM
- p. 20 Reference [97]
Wijffels SE
Judge's note: Viewed pp. 19 and 20. Every other author in [76] has initials; 'Wijffels' has none, and [97] gives the same author as 'Wijffels SE'.
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Typo Reference [58] gives an impossible page range: "Science 2006; 314: 1556-11557." (presumably 1556-1557).
- p. 19 Reference [58]
Science 2006; 314: 1556-11557
- p. 19 Reference [58]
Science 2006; 314: 1556-11557.
- p. 19 Reference [58]
314: 1556-11557
Judge's note: Viewed p. 19: the end page is printed as 11557. The range would span about ten thousand pages for a short Science item; a duplicated digit is the evident cause.
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Typo Reference [73] prints the third author as "Barnett TP, Adam JC, Lettenmaler DP"; the author's surname is believed to be Lettenmaier.
- p. 19 Reference [73]
Barnett TP, Adam JC, Lettenmaler DP
- p. 19 Reference [73]
Lettenmaler DP
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that the third author of Barnett, Adam and Lettenmaier, Nature 2005; 438: 303-309 is spelled Lettenmaier. In the enlarged crop of p. 19 the glyph after 'ma' is an undotted 'l', and the text layer agrees, so this is not a rendering or extraction artefact.
Second check: none (judge only)