Friday, June 1, 2018

+Myth: An Ice Core Shows a Spike in CO2 Levels without a Spike in Temperature

The outline for this post is as follows:
  1. The Myth and Its Flaw
  2. Context and Analysis
  3. Posts Providing Further Information and Analysis
  4. References

This is the "+References" version of this post, which means that this post contains my full list of references and citations. If you would like an abbreviated and easier to read version, then please go to the "main version" version of this post.

References are cited as follows: "[#]", with "#" corresponding to the reference number given in the References section at the end of this post.

1.  The Myth and Its Flaw

The myth claims that an Antarctic ice core revealed a recent rise in carbon dioxide (CO2) levels, without a concurrent rise in temperature. Thus recent CO2 increases did not cause much recent warming.

Proponents of this myth include Tony Heller (a.k.a. Steven Goddard) [1, from 11:26 to 13:42; 2; 37; 38], Javier of Judith Curry's Climate Etc. blog [51, figure 110], Iowa Climate Science Education [41], Patrick Moore [3], Suspicious0bservers (a.k.a. Ben Davidson) [40], CO2IsLife [39], and various climate science critics online [4; 5; 36].

The myth's flaw: The ice core in question lacks data after ~1912 [6; 10; 11]. So myth proponents use images that add post-1912 CO2 data to the ice core, without adding post-1912 temperature data [1, from 11:26 to 13:42; 2 - 5; 36 - 41; 51, figure 110]. Thus these images lack a temperature spike due to this lack of recent temperature data, not because CO2 does not cause warming. Furthermore, contrarians cherry-pick recent temperature from one location in Antarctica [1, from 11:26 to 13:42; 2 - 5; 36 - 41; 51, figure 110], in order to ignore warming over the rest of the planet [18; 27; 52 - 69]. They also ignore the fact that Earth has not reached an equilibrium state in which all the warming from the CO2 rise has occurred [23, section 5.2 on page 1373; 24, sections 2.3 and 2.4 on pages 5 - 6; 47 - 50]. Thus myth proponents are being (intentionally or unintentionally) misleading when they use their images to argue that CO2 did not cause much recent warming.

(I present evidence that increased CO2 caused most of the recent global warming in "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation".)

potholer54, a.k.a. Peter Hadfield, also addresses Tony Heller's defense of the myth. potholer54 does this by citing published evidence to explain why Antarctic temperature trends during recent industrial-era global warming should not be expected to follow the Antarctic temperature patterns reflected in the ice core record for warming in the most distant past. This is because:

  • the initial trigger for warming in the ice core record was changes in Earth's absorption of solar radiation in the southern hemisphere, the hemisphere in which Antarctic is located, while the trigger for industrial-era warming was greenhouse gas release predominately in the northern hemisphere
  • man-made ozone-depletion indirectly made significant contributions to industrial-era Antarctic temperature trends, while there is not evidence of ozone-depletion contributing much to Antarctic temperature trends in the ice core record for the distant past
  • Antarctica has had less time to respond to recent warming, since industrial-era global warming occurred over a shorter time than warming in ice core record

Thus potholer54 rebuts the myth [93, from 12:47 to 15:04] in a different way than I do, though our explanations remain compatible. So I will not focus on potholer's rebuttal in my discussion in section 2 below.

2. Context and Analysis

Scientists justifiably use correlation between two factors as part of a cumulative case for a causal relationship between those two factors, as I discuss in "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation". In light of this, some individuals attempt to undermine the case for CO2-induced warming by showing that recent CO2 increases do not correlate with recent temperature changes. Some of these individuals estimate past temperature changes and CO2 levels using proxy data from ice cores in Antarctic. They argue that these ice cores show a recent CO2 rise without a recent rise in temperature; thus increased CO2 does not correlate with recent warming, and CO2 did not cause most of the recent warming [1, from 11:26 to 13:42; 2 - 5; 36 - 41; 51, figure 110]. This is the myth this blogpost focuses on.

Below are several images myth proponents present to make their case:

Figure 1: Images arguing against recent, man-made, CO2-induced global warming by comparing estimates of CO2 levels and temperature changes. The estimates are (supposedly) based on data from an Antarctic ice core [1, from 11:26 to 13:42; 2 - 5; 36 - 38; 40; 41].

But these graphs are very misleading, which becomes clear when one examines the original data analysis for the Antarctic ice core:

Graph of temperature change and carbon dioxide change measured from the EPICA Dome C ice core in Antarctica

Figure 2: CO2 level and temperature change estimated from an Antarctic ice core [6]. The data is taken from two published studies [7; 8]. "Years before present" (BP) for ice cores means "years before 1950" [9]; this point sometimes confuses contrarians [86, from 8:13 to 9:10; 87, page 95; 88, from 5:33 to 7:52; 90]. And the aforementioned data stops by about 38 BP [10; 11], which is equivalent to ~1912. So this figure does not include most of the warming and CO2 increase since the 20th century; CO2 levels are now above 405ppm [12]. 1°C of Antarctic warming translates to ~0.6°C of global warming [13].

(In section 2.8 of "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation", I rebut the argument that figure 2 undermines the case for CO2-induced warming, since figure 2 shows that CO2 increases lag temperature increases.)

Thus figure 1's recent CO2 increase from 280 parts per million (ppm) to ~400 ppm was not present in the original Antarctic analysis presented in figure 2. This CO2 spike instead likely came from data collected in Mauna Loa, Hawaii up to the year 2015 [12]. Figures 2's CO2 and temperature estimate stops by about 38 "years before present" [10; 11], where "years before present" means "years before 1950" for ice cores [9]. So the ice core estimate stops by about 1912. Myth advocates add recent CO2 data to this analysis without adding recent temperature data. They then use this to argue against CO2 causing recent global warming [1, from 11:26 to 13:42; 2 - 5; 36 - 41; 51, figure 110]. But the myth defenders' argument fails, since the myth proponents excluded the recent temperature data needed to justify their conclusion.

When I pointed this out [35] this evidence to the debunked [116 - 119] myth proponent [1, from 11:26 to 13:42; 2; 37; 38] and conspiracy theorist [108 - 115] Tony Heller (a.k.a. Steven Goddard), this was his entire response:

"What a load of BS [35]."

Thus Tony Heller resorts to denialism in order to defend his myth. Science denialists refuses to accept scientific claims supported by strong evidence [33, page 1; 34, section 5; 70; 71 - 73; 74, pages 239 and 240; 75, section 2; 76 - 79; 80, page 1; 81]. The following sources provide further context on what denialism is:

"It is, however, important not to confuse denialism with genuine scepticism, which is essential for scientific progress. Sceptics are willing to change their minds when confronted with new evidence; deniers are not [33]."

"The crucial difference is that your colleagues will accept a scientific statement if provided with sufficiently strong reasons to do so. In contrast, climate science denialists, like other pseudoscientists, tend to be driven by motives that make them impossible to convince, however strong the arguments they are presented with [34]."

So what do recent Antarctic temperature trends show? Figure 3 helps answer this question by presenting temperature trends from Antarctica and other regions on Earth:

Figure 3: Temperature trends since AD 1500 in different regions. 15-year trends are shown as thin black curves and 50-year trends are shown as thick black curves. The vertical black bar indicates the median time at which sustained, significant industrial-era warming began in that region. The gray 1°C scale bar represents 1K of temperature change on the y-axis for each regional temperature trend [18, figure 2 on page 413].

So despite the fact that some Antarctic regions warmed [17; 21; 22; 64, figure 1; 89; 94; 95; 99; 100] with analyses showing Antarctic surface warming [28 and 29, generated using 102, as per 103; 55, figure 2; 63, figure 7; 64, figure 1; 89; 91, figure 4; 94; 99; 100; 107] and warming of the lower atmosphere [101; 104; 105; 107], Antarctica and the Southern Ocean as a whole most likely did not significantly warm [18, figure 2 on page 413; 19, figure 3 on page 921; 20; 30 - 32, generated using 102, as per 103; 95] (though there is significant uncertainty for 20th century Antarctic temperature records [18, page 412; 27; 99], , with some results suggesting cooling of the Antarctic lower atmosphere [105; 106]). Some early climate models projected this result [25, from 31:48 to 33:33; 26, figure 3 on page 661], while Antarctic temperature trends are on the very low end of the range of projections from some later climate models [19, figure 3 on page 921]. So the lack of robust Antarctic warming in figure 3 is not a total surprise. 

Myth proponents engage in cherry-picking if they use this Antarctic trend to argue against recent global warming, especially since figure 3 shows warming elsewhere in the world and there is abundant evidence of Earth's surface warming [18; 27; 52 - 69]. In contrast, figure 2 does not commit cherry-picking, since climate scientists also use proxies outside of Antarctica to confirm warming [82 - 85]. But suppose Antarctic proxies were the only proxies available for temperature changes in the distant past. Then scientists would still not be guilty of cherry-picking in their use of figure 2, because the charge of cherry-picking does not apply in situations where one only has one option to choose from.

Returning from warming in the distant past to more recent warming: the industrial-era warming from figure 3 likely under-estimates the warming caused by CO2 increasing from 280ppm to ~405ppm. This is due to thermal inertia [42 - 46; 92; 96 - 98] and the fact that Earth has yet to reach an equilibrium state [23, section 5.2 on page 1373; 24, sections 2.3 and 2.4 on pages 5 - 6; 47 - 50; 92; 96] in which Earth stops warming because Earth's release of energy into space matches the solar energy Earth takes in [14 - 16] (I discuss this more in sections 2.2, 2.5, and 2.8 of "Myth: Attributing Warming to CO2 Involves the Fallaciously Inferring Causation from a Mere Correlation"). So even if myth proponents modified figure 1 to include industrial-era global warming, they would still fail in their goal of arguing that CO2 does not cause a significant amount of global warming.

3. Posts Providing Further Information and Analysis

4. References

  1. Youtube, Tony Heller's video: "The Climate Control Knob"
  6. "Temperature change and carbon dioxide change":
  7. "High-resolution carbon dioxide concentration record 650,000–800,000 years before present"
  8. "Orbital and millennial Antarctic climate variability over the past 800,000 years"
  9. ("800,000-year Ice-Core Records of Atmospheric Methane (CH4)")
  10. (Data for "Orbital and millennial Antarctic climate variability over the past 800,000 years")
  11. (Data for "High-resolution carbon dioxide concentration record 650,000–800,000 years before present")
  13. "Evolution of global temperature over the past two million years"
  14. "Feedbacks, climate sensitivity and the limits of linear models"
  15. "The equilibrium sensitivity of the Earth’s temperature to radiation changes"
  16. "Climate sensitivity in the geologic past"
  17. "Central West Antarctica among the most rapidly warming regions on Earth" ("Corrigendum: "Central West Antarctica among the most rapidly warming regions on Earth"")
  18. "Early onset of industrial-era warming across the oceans and continents" ["Corrigendum: Early onset of industrial-era warming across the oceans and continents"]
  19. "Assessing recent trends in high-latitude Southern Hemisphere surface climate"
  21. "Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year"
  22. "Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century"
  23. "Misdiagnosis of Earth climate sensitivity based on energy balance model results"
  24. "Target atmospheric CO2: Where should humanity aim?"
  25. Ray Pierrehumbert's 2012 video: "Tyndall Lecture: GC43I. Successful Predictions - 2012 AGU Fall Meeting"
  26. "Interhemispheric asymmetry in climate response to a gradual increase of atmospheric CO2"
  27. "Coverage bias in the HadCRUT4 temperature series and its impact on recent temperature trends"
  33. "How the growth of denialism undermines public health"
  34. "Dealing with climate science denialism: experiences from confrontations with other forms of pseudoscience"
  35. (Comment from early May 2018 in the comments section of Youtube, Tony Heller' video: "The Climate Control Knob";
  42. "On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead"
  43. "The climate change commitment" (DOI: 10.1126/science.1103934)
  44. "Stabilizing climate requires near‐zero emissions"
  45. "How much warming are we committed to and how much can be avoided?"
  46. "Irreversible climate change due to carbon dioxide emissions"
  47. "Improved estimates of ocean heat content from 1960 to 2015"
  48. "Insights into Earth’s energy imbalance from multiple sources"
  49. Stephens and L'Ecuyer: "The Earth's energy balance"; doi: 10.1016/j.atmosres.2015.06.024
  50. "Reconciling estimates of ocean heating and Earth’s radiation budget"
  52. "Estimating changes in global temperature since the preindustrial period"
  53. "Global temperature evolution: recent trends and some pitfalls"
  54. "A reassessment of temperature variations and trends from global reanalyses and monthly surface climatological datasets"
  55. "Recent United Kingdom and global temperature variations"
  56. Hansen et al.: "Global temperature in 2015"
  57. "Possible artifacts of data biases in the recent global surface warming hiatus"
  58. "On the definition and identifiability of the alleged “hiatus” in global warming"
  59. "Independent confirmation of global land warming without the use of station temperatures"
  60. "A global multiproxy database for temperature reconstructions of the Common Era"
  61. "Global and hemispheric temperature reconstruction from glacier length fluctuations"
  62. "Global warming in an independent record of the past 130 years"
  63. "A new integrated and homogenized global monthly land surface air temperature dataset for the period since 1900"
  64. "Global land-surface air temperature change based on the new CMA GLSAT dataset"
  65. "Land surface temperature over global deserts: Means, variability, and trends"
  66. "Assessing recent warming using instrumentally homogeneous sea surface temperature records"
  67. "Assessing the impact of satellite-based observations in sea surface temperature trends"
  68. "A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change"
  69. "An ensemble of ocean reanalyses for 1815–2013 with sparse observational input"
  70. "Denialism: what is it and how should scientists respond?"
  74. "AIDS denialism and public health practice"
  75. "The ethics of belief, cognition, and climate change pseudoskepticism: Implications for public discourse"
  76. "Science denial: a guide for scientists"
  77. "Commentary: Questioning the HIV-AIDS hypothesis: 30 years of dissent"
  78. "HIV denial in the internet era"
  79. "Errors in Celia Farber's March 2006 article in Harper's Magazine"
  80. "Countering evidence denial and the promotion of pseudoscience in autism spectrum disorder"
  81. "Commentary to: How to respond to vocal vaccine deniers in public"
  82. "Synchronous change of atmospheric CO2 and Antarctic temperature during the last deglacial warming"
  83. "Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation"
  84. "Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions"
  85. "Tightened constraints on the time-lag between Antarctic temperature and CO2 during the last deglaciation"
  86. Youtube, potholer54's video: "23 -- Medieval Warm Period -- fact vs. fiction"
  87. "Correction to: A 2000-year global temperature reconstruction based on non-tree ring proxies"
  88. Youtube, potholer54's video: "Response to Bill Whittle's "Is climate change real?""
  89. "An assessment and interpretation of the observed warming of West Antarctica in the austral spring"
  90. "Comments on Loehle,“Correction to: A 2000-Year Global Temperature Reconstruction Based on Non-Tree Ring Proxies”, E&E, 18 (7 and 8), 2007"
  91. "Land surface air temperature data are considerably different among BEST‐LAND, CRU‐TEM4v, NASA‐GISS, and NOAA‐NCEI"
  92. "Earth's energy imbalance: Confirmation and implications"
  93. Youtube, potholer54's video: "Response to Tony Heller"
  94. "New reconstruction of Antarctic near-surface temperatures: Multidecadal trends and reliability of global reanalyses"
  95. "Antarctic climate variability on regional and continental scales over the last 2000 years"
  96. "Committed warming inferred from observations"
  97. "Maximum warming occurs about one decade after a carbon dioxide emission"
  98. "The time lag between a carbon dioxide emission and maximum warming increases with the size of the emission"
  99. "An assessment of recent global atmospheric reanalyses for Antarctic near surface air temperature"
  100. "Recent land surface temperature patterns in Antarctica using satellite and reanalysis data"
  101. "Half-century air temperature change above Antarctica: Observed trends and spatial reconstructions"
  102. "Web-based Reanalysis Intercomparison Tool: Monthly/seasonal time series"
  103. "Web-Based Reanalysis Intercomparison Tools (WRIT) for analysis and comparison of reanalyses and other datasets"
  104. "Significant warming of the Antarctic winter troposphere"
  105. "Antarctic atmospheric temperature trend patterns from satellite observations"
  106. "The reliability of Antarctic tropospheric pressure and temperature in the latest global reanalyses"
  107. "Radiosonde-observed vertical profiles and increasing trends of temperature and humidity during 2005–2018 at the South Pole"
  108. []
  109. []
  110. []
  111. [ ; "Goddard’s regular conspiracy theory about CIA drug use to brainwash school kids into shooting incidents in order to disarm conservatives in preparation for concentration camps for conservatives is something skeptics should stop ignoring and start actively shunning. His blog is the crack house of skepticism."]
  112. []
  113. []
  114. []
  115. []
  116. []
  117. []
  118. []
  119. []

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