The 2.5% – contrarian climate change papers in Cook et al. (2013)

Cook et al (2013) surveyed almost twelve thousand abstracts to determine how many papers accepted climate change. They found that the overwhelming majority of abstracts that took a position supported the consensus that humans are affecting climate change. This is hardly a surprise to anybody remotely familiar with the literature, but it brought forth froth from the usual places.

The only thing I find surprising is that Cook et al found so many papers rejecting the consensus. I want to look at these contrarian papers and ask if they are good papers with coherent alternative views of climate, or if they show profound disregard for the basics of physics, chemistry, statistics or logic.

I am aware that this is a one-sided exercise; papers that support the consensus can also be bad papers.

I’m going to start with the nine papers ranked by Cook et al as

(7) Explicit rejection with quantification: Explicitly states that humans are causing less than half of global warming

as these represent the most extreme case of rejection of the consensus.

Baliunas & Jastrow (1993) Evidence On The Climate Impact Of Solar VariationsEnergy

Baliunas & Jastrow (1993) try to estimate how variable the sun’s output is. Their estimate of 0.1-0.7% is large compared to the estimates in IPCC AR4, but comparable with older estimates. The conclusion that solar forcing could explain most of the temperature rise in the 20th centrury is based on the correlation between solar cycle length and global temperature in Friis-Christensen and Lassen (1991), a correlation that was inflated by smoothing and errors in the solar record and that breaks down when the the post-1985 temperature and solar data are considered (Stauning, 2011). Baliunas and Jastrow’s paper may have been credible in 1993, it no longer is.

Khilyuk & Chilingar (2003) Global Warming: Are We Confusing Cause And Effect?, Energy Sources

Khilyuk & Chilingar (2003) argue that global warming is due to increased solar activity and that the increase in atmospheric CO2 concentration is due to oceanic out-gassing.

After dismissing an energy-balance model for ignoring convection (which is actually a minor term in the Earth’s energy budget (Trenberth & Stepaniak, 2006)), the paper begins with an account of adiabatic temperatures. Eli Rabbet was not impressed by this model in a subsequent paper. The authors make no attempt to demonstrate how Earth can be as warm as it is without a greenhouse effect.

The paper calculates the change in temperature due to the change in atmospheric pressure  resulting from CO2 release (apparently ignoring O2 consumed by combustion). This calculated change is very small. This is not in the least surprising – nobody expects CO2 pressure-induced heating to be in the least important. Khilyuk & Chilingar (2003) ignore the radiative impact of CO2 when concluding that CO2 has negligible impact on climate.

The argument that the increase in atmospheric CO2 is due to out-gassing from the warming oceans is false. Atmospheric CO2 concentrations have increased by less than the amount of CO2 released by human activity – about half of the CO2 released must have been absorbed by natural sinks. The amount of CO2 in the ocean is increasing, and the pH decreasing, as the oceans absorb anthropogenic CO2.

Their evidence that climate is solar forced is a graph of temperature against the length of the solar cycle. The graph bears no resemblance to the graph it claims to be modified from.

Khilyuk & Chilingar (2004) Global Warming And Long-term Climatic Changes: A Progress Report, Environmental Geology

This paper is essentially a duplicate of Khilyuk & Chilingar (2003), recycling most of the arguments and much of the text. Duplicate publications are contrary to ethical guidelines, although apparently in this case it was approved by the editors. One of the problems with duplicate publications is that the work can be double counted by meta-analyses, as Cook et al (2013) have done with this paper.

Khilyuk & Chilingar (2006) On Global Forces Of Nature Driving The Earth’s Climate. Are Humans Involved?, Environmental Geology

Another truly dreadful paper by Khilyuk & Chilingar, recycling many of the errors in their previous papers and adding some novel ones. It is rebutted at length by Aeschbach-Hertig (2007).

My favourite claim is that the total anthropogenic carbon dioxide emission “constitutes less than 0.00022% of the total CO2 amount naturally degassed from the mantle during geologic history.” Comparing two centuries of emissions with those of the previous 4.5 billion years? Madness – rates of emissions matter.

Chilingar, Sorokhtin, Khilyuk & Gorfunkel (2009) Greenhouse Gases And Greenhouse Effect, Environmental Geology

This paper repeats many of the errors in the Khilyuk & Chilingar papers.

Essenhigh (2009) Potential Dependence Of Global Warming On The Residence Time (rt) In The Atmosphere Of Anthropogenically Sourced Carbon Dioxide, Energy & Fuels

Essenhigh (2009) argues that because the residence time of a CO2 molecule in the atmosphere is short, the modern increase in atmospheric CO2 concentration cannot be caused by humans, but must be due to natural sources. In a very patient comment, Crawley (2011) explains why this is wrong.  Simply, the rise in atmospheric CO2 is less that that emitted by human activity, therefore the oceans and land vegetation must be a net sink for anthropogenic CO2 and cannot be a net source. Crawley (2011) has a nice analogy of euro coins in a jar that shows that a short residence time of individual coins is not relevant to the long term trends in the number of coins.

Scafetta (2010) Empirical Evidence For A Celestial Origin Of The Climate Oscillations And Its Implications, Journal Of Atmospheric And Solar-terrestrial Physics

Scafetta (2010) argues that there is a sixty year cycle in global temperature data and that this can be explained by celestial forcing. A similar paper, Scafetta (2012) has been criticised by Benestad et al. (2013) on numerous grounds: the 160 year temperature record is too short to reliably extract a 60 year cycle; there is no physical mechanism for the weak gravity of other planets to have large effects on Earth’s climate; a quadratic trend is left unexplained. Scafetta (2010) is an unvalidated curve fitting exercise. It is not credible.

Sarkisyan (2010) On Some Achievements And Major Problems In Mathematical Modeling Of Climatic Characteristics Of The Ocean (critical Analysis), Izvestiya Atmospheric and Oceanic Physics

Sarkisyan (2010) is a mathematically complex discussion of currents in climate models which I am not competent to evaluate. The main conclusion is that high-resolution models are required to precisely model currents, but the recommendation of resolutions of 0.055° or even 0.01° are not feasible for GCMs without orders of magnitude more computing power. Global warming is not discussed in the body of the paper, only in the discussion where the paper declares

Thus, the conclusion is that present-day models with a resolution of no less than (1/18)° are unable to answer the question about the presence of global warming or cooling. The available observed data also provide no evidence of this fact. The study [29] indicates that the temperature in the upper layer of the World Ocean over the second half of the past century has increased by 3° in some regions and decreased by the same magnitude in others. On average, there is no stable warming or cooling trend. If this has not been proven for the ocean, it has not been proven for the atmosphere either.

The second claim, that because some areas have warmed while others have cooled there is no trend on average is simply wrong, as a cursory glance at the data will show. The claim that there is no atmospheric warming either is equally absurd. This blatant rejection of reality makes it difficult to accept the first claim at face value, especially when even a zero-dimensional energy-balance model can do a reasonable job of diagnosing global warming.

The rejection of global warming in the abstract of Sarkisyan (2010) is not supported by the contents of the paper.

Zhao (2011) Is Global Warming Mainly Due To Anthropogenic Greenhouse Gas Emissions?Energy Sources Part A-Recovery Utilization and Environmental Effects

Zhao (2011) uses regression models to test if there is a relationship between CO2 and temperature for the United States over the years 1990-2005. I can already tell that this is not going to end well, as it is unlikely that a significant relationship will be found in such a short time period and limited geographical area. It gets worse. Rather than testing the relationship between CO2 concentrations and temperature, Zhao (2011) tests the relationship between CO2 emissions and changes in temperature. This is a detrending step that will throw away any temperature trends and focus on the year-to-year weather-driven variability (the paper explicitly assumes that the impact of El Nino is zero). This is an analysis that stood no chance of detecting the impact of CO2 on climate, but it gets worse still. The analysis is done on a state by state basis: temperature changes in Montana are correlated with emissions in Montana. Even if the rest of the analysis was sensible, this last part is not as it assumes that CO2 does not mix across state borders. This is a tragically bad paper.


None of the nine papers rated by Cook et al (2013) as “Explicit rejection with quantification” are credible in rejecting the consensus on global warming.

Next I’ll look at the 15 papers rated as “Explicit rejection without quantification: explicitly minimizes or rejects that humans are causing global warming” to see if they are any more credible.


About richard telford

Ecologist with interests in quantitative methods and palaeoenvironments
This entry was posted in climate, Peer reviewed literature, solar variability and tagged . Bookmark the permalink.

3 Responses to The 2.5% – contrarian climate change papers in Cook et al. (2013)

  1. Amy says:

    I guess “someone” could always analyse a randomly-drawn equal number of the papers that support anthropogenic global warming, to look at quality and duplication (am I getting ahead of the blog author here perhaps?) Given that Cook et al. looked at something like 12,000 abstracts I can’t blame them for not doing quality assessment, particularly given that their aim was only to quantify ‘consensus’.

    • Quality assessment is hard – unless the authors are making very obvious or common errors, you need to be an expert in the particular field to spot them. It takes a long time – much longer than just rating an abstract. It is also contentious – the authors may agree with Cook et al’s ratings, but probably not with my assessment

  2. Pingback: On the NIPCC, the sun, moths and flames | Musings on Quantitative Palaeoecology

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