Review of Inconvenient Facts, Part 2 - Temperature
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| Pages 2K Reconstruction of Global Temperatures Replicating MBH98/99 |
In a previous post, I wrote an initial review of Gregory Wrightstone's Book, Inconvenient Facts. We began to see that Mr. Wrightstone's book was pretty low on facts and high on convenience - that is, Wrightstone's claims would be very convenient for us if we believe him, since if there is no problem, we have no compelling reason to fix a non-existent problem. That post covered only the first two chapters of his book. Chapter 3 is supposed to contain more inconvenient facts about temperature, but what we get is a lot of misinformation about temperature based on 1) the rejection of scientific evidence about temperature and 2) the confusion of global temperatures with local temperatures, including 2a) Central England and 2b) the Greenland summit, and 3) the misuse of a terrible proxy reconstruction.
Confusion About Proxies
Mr. Wrightstone (somewhat) correctly observes that, if global (or Northern Hemisphere) temperatures over the last 2000 years have a "hockey stick" shape, with the blade coinciding with anthropogenic increase of GHG emissions, that would be a compelling argument that humans hare affecting climate. He writes,
If Mann’s depiction of temperature over the last millennium were correct, then his work might form a solid basis for recent warming being mostly man-made.[1]
Of course, the temperature record alone is not proof that the blade of the hockey stick is human caused, but it would validate several predictions of climate science. The evidence shows that the near 50% increase in CO2 emissions (combined with other GHGs and aerosols) should produce a measurable increase in global temperatures, and that's what we find. In a previous post, I show how the "hockey stick" conforms to the expectations of known physics regarding the greenhouse effect. So it's somewhat unsurprising that Mr. Wrightstone feels it necessary to deny the validity of the reconstruction. His two objections are that Mann's hockey stick was 1) based on unreliable proxies and 2) statistically flawed.
The first objection contains no evidence. It contains only bare assertions. He writes,
Even the scientists who provided the data for the bristlecone-pine series gave specific warnings against using it for temperature reconstruction. Mann used the data anyway. It provided the results he wanted. Not only did he use questionable proxies, he cherry-picked a relatively small number of tree-rings and ignored a greater number of trees from the same area that did not show the results that he desired.[1]
He cites no evidence of this, nor does he acknowledge what MBH98/99[2][3] actually actually did. He seems to think that MBH98 was limited to tree ring proxies and so was limited by the uncertainties of that proxies. He gives no source for warnings from the IPCC and other scientists that tree ring proxies are unreliable. I guess we're just supposed to take his word for it. But Mann's paper was not limited to tree ring proxies:
We use a multiproxy network consisting of widely distributed high quality annual-resolution proxy climate indicators, individually collected and formerly analysed by many palaeoclimate researchers...The network includes (Fig. 1a) the collection of annual resolution dendroclimatic, ice core, ice melt, and long historical records used by Bradley and Jones combined with other coral, ice core, dendroclimatic, and long instrumental records.[2]
Tree ring (denrochomatic) proxies were one among many types of proxies used by MBH98/99, and the diversity of proxies helps shrink the uncertainty from relying on only one proxy. Mr. Wrightstone does not tell us what he thinks these problems with tree ring proxies were, but almost certainly it has to do with the "divergence problem," which identified unreliability in tree ring proxies from ~1960 onward. But also in a previous post, I showed that the divergence problem affected Briffa's proxy because it relied exclusively on tree rings, but it did not affect Mann's time series. This is why Jones only "hid the decline" in Briffa's time series and not Jones' or Mann's.
Wrightstone's second objection is that MBH98/99 are statistically flawed, but he doesn't make a coherent argument that this is the case. Rather, he relies on some work by McIntyre and McKitrick (MM) that challenged the statistical veracity of the MBH98/99 reconstruction. As summarized by Mr. Wrightstone, partly quoting the paper,
Mann’s hockey-stick reconstruction of changes in the Earth’s temperature was “primarily an artefact (sic) of poor data handling, obsolete data and incorrect calculation of principal components."
That is basically what McIntyre and McKitrick concluded, but just because they concluded this doesn't mean the analysis was correct or even particularly informed. In other posts I've gone through the relevant papers from MM and the responses by MBH and other scientists. The initial MM critique of MBH98 was published in the journal Energy & Environment in 2003, and that journal is not peer-reviewed in any meaningful sense. In fact, there is good evidence that the reason their paper was published there was due to the potential policy impact of the paper. The editor for Energy & Environment, Ms. Sonja Boehmer-Christiansen, even admitted in an email to Dr. Tim Osborn of CRU that she even rushed the publication of the paper for policy reasons: "I was rushing you to get this paper out for policy impact reasons, e.g. publication well before COP9” and even admitted that the “paper was amended until the very last moment. There was a trade off in favour of policy.”[4] MM's critique display the lack of experience in climate science and proxy data - McIntyre works in the mining industry and McKitrick is an economist. MM's criticisms of MBH98 by MM have no merit. To summarize:
1. Rutherford et al 2005[5] was able to replicate the conclusions of MBH98/99 using a different methodology, directly contradicting MM's claim that the hockey stick was a product of a flawed methodology instead of the actual variation in temperature.2.Wall & Ammann 2007[6] reexamined MBH98 and found the temperature reconstructions to be robust, and the proposed “corrections” to MBH from MM were found to be “without statistical and climatological merit.” In fact, the MM "corrected" reconstructions were the result of "ignoring... key data" and failed "basic tests for statistical validity." Mann summarizes the Wall and Ammann study as "This means that the reconstructions McIntyre and McKitrick produced are statistically inferior to the simplest possible statistical reconstruction: one that simply assigns the mean over the calibration period to all previous reconstructed values."[4]
3. About 10 years later, Mann published an update to his MBH98/99 studies confirming the “hockey stick” is robust over the last 1300 years, whether or not tree ring proxies are used.[7]
4. About 50 papers have been published following MBH98 that have replicated MBH98’s “hockey stick” graph.[8] Even if we rejected MBH98 entirely, literally nothing would change in climate science. Current studies are more robust with a more extensive proxy database, and they all reaffirm the general “hockey stick” shape to global temperatures over the last 2000 years; see for instance the Pages 2K studies.[9][10] Since Pages2K has been available since 2013, Mr. Wrightstone has no excuse for failing to acknowledge the fact that the Hockey Stick had already been replicated multiple times before he self-published his book in 2017. I know of no reconstruction of global or hemispheric temperatures of the last 2000 years that does not have a hockey stick shape.
4. About 50 papers have been published following MBH98 that have replicated MBH98’s “hockey stick” graph.[8] Even if we rejected MBH98 entirely, literally nothing would change in climate science. Current studies are more robust with a more extensive proxy database, and they all reaffirm the general “hockey stick” shape to global temperatures over the last 2000 years; see for instance the Pages 2K studies.[9][10] Since Pages2K has been available since 2013, Mr. Wrightstone has no excuse for failing to acknowledge the fact that the Hockey Stick had already been replicated multiple times before he self-published his book in 2017. I know of no reconstruction of global or hemispheric temperatures of the last 2000 years that does not have a hockey stick shape.
We don't have time to go into a full critique of MM's critique in a review of Mr. Wrightstone's book. You can read more about that here. But what should be acknowledged here is that Mr. Wrightstone had access to all of this information and provided none of it. He leads you to believe that MM's critique is competent and valid, and even concludes from this (quoting someone else) that "We now know that the hockey stick is fraudulent." But he supplied no evidence of fraud, none whatsoever.
Confusing the Correlation between CO2 and Temperature
Following his unsupported attack on the "hockey stick," Mr. Wrightstone attempts to show that there is low to no correlation between CO2 and global temperature in the instrumental record. He breaks up the instrumental record into pieces, before 1945, from 1945 to 1976, from 1976 to 1998 and from 1998 to 2017 (sort of). He then points to two time frames (1945-1976 and 1998-2015) where temperatures paused while CO2 increased. He then writes,
Significant carbon dioxide emissions didn’t start ramping up until shortly after the end of the Second World War. Yet, since 1945, more than 70% of that time frame included periods of either declining or flat temperatures.
And it's true that from 1945 to 1976, temperatures were roughly stable and may have cooled a little bit while CO2 rose. What he doesn't tell you is that during WWII we also blew up a lot of stuff, and the ramping up of industrialization polluted the air with aerosols, which exert a strong cooling influence on climate. They reflect sunlight back to space before it can be absorbed at the earth's surface. This cooling influence from aerosols explains the pause from the 1940s to 1970s - a significant period of ~30 years - but it's well explained within climate science. CO2 and aerosols increased and the radiative forcing increase from CO2 was roughly balanced by the decrease from aerosols, so temperatures stabilized.
The second claimed "pause" is short, far less than the post WWII pause. This "pause" was from 1998-2014 (2015 became the hottest year on record until surpassed by 2016), or 17 years, and it's merely the product of internal variability. It turns out that 1998 was an extremely large El Nino year, and so if you cherry pick 1998 as a start date and then choose only short-term time frames (before the next El Nino), you can create the impression of a "pause," but the trend that is claimed to be a pause is not statistically significant. I've written another post about the effect of El Nino on short-term trends, showing that this kind of cherry picking is always going to produce misleading results. I've also written on failed attempts to justify claiming a pause exists from statistically insignificant data. Mr. Wrightstone simply cherry picked a short-term time frame (1998-2015) and then ignored the statistical insignificance of his evidence that here was a "pause." It turns out that from 1998 to present (24 years), the trend has been 0.214 ±0.083 °C/decade (2σ). In recent decades, once you choose enough years to get a statistically significant trend, you also get statistically significant warming.
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| NASA's GMST Trend since 1998 |
Wrightstone's attempts to show a lack of correlation between CO2 and temperature universally fail because he simply does not show you the data in a form that allows you to assess that correlation. He plots CO2 and temperature as two time series, which allows him to choose scales for each that can obscure the correlation. But if you plot CO2 as radiative forcing on the x-axis and GMST on the y-axis, you get a linear trend, and the slope of that trend will approximate TCR. The r^2 will show you the correlation. If you do that, you get an r^2 of 0.87 and a TCR of about 2.25 C for doubling CO2.
%20(6)%20(1).png) |
| The Slope of this Line indicates a TCR of 2.25 C |
Confusing Global Temperature with Local Temperatures
What follows in this chapter contains what he considers to be "be some of the most important in the entire book," but they depend largely on confusing local temperatures with global temperatures, whether they be Central England or Central Greenland. For instance, here's an example of Mr. Wrightstone confusing Central England with the globe.
I've also documented elsewhere Mr. Wrightstone's confusion of global temperatures with the temperatures of Central Greenland. This is not uncommon. Many contrarians depend on this confusion. The trick is to plot the ice core data with a single proxy from a single ice core (GISP2 in Central Greenland) and then make claims about global temperatures. For instance, Wrightstone claims,
The damning data show that, for more than 6,100 years (or 60%) of the current interglacial warm period, the temperature was warmer than it is today. Of the nine earlier significant periods of warming since the end of the last ice age, five had higher rates of temperature increase... and seven had larger total increases in temperature. Moreover, each of the previous warming cycles experienced significantly higher temperatures than today."I provided a detailed rebuttal of this claim here, so I don't feel compelled to reproduce the documentation and evidence. In point of fact global temperatures are warmer than at any time in the Holocene, even if local Greenland temperatures have not yet exceeded the warmest Holocene Greenland temperatures yet, due to orbital cycles, etc. But the current rate of Arctic warming is about 3 to 4 times larger than at any point detectable in the GISP2 ice core.
Confusion About Loehle's Proxy Reconstruction
One other aspect of this chapter that deserves some attention is his attempt to claim the Medieval Warm Period was warmer than today from Loehle 2008's proxy study, published in Energy & Environment. Mr. Wrightstone's version of this reconstruction is below.
With the corrected dating, the number of series for which data is available drops from 11 to 8 in 1935, so that subsequent values of the reconstruction would be based on less than half the total number of series, and hence would have greatly decreased accuracy. Accordingly, the corrected estimates only run from 16 AD to 1935 AD, rather than to 1980 as in Loehle (2007).
Then it says that the MWP was "0.412 Deg C above the last reported value at 1935." This is is what Loehle's corrected study actually concluded. Mr. Wrightstone quoted the previous 2007 study with the erroneous conclusion. He also got the last date in the time series wrong - it's not 1949; it's 1935. Loehle's conclusion, though, with the MWP being only 0.412 C warmer than 1935, means that there has been 87 years of warming not included in Loehle's reconstruction.
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Confusion about Scotese' Temperature Schematic
In Mr. Wrightstone's "facts" about geologic history on time scales of millions to billions of years, he makes use of a schematic that was made by Christopher Scotese in 2002 and placed on his website. This is what Mr. Wrightstone says about it.
Figure I-34, showing more than 4 billion years’ temperature data as adapted from Scotese (2002), reveals that the Earth is now in one of the coldest periods in its history. No geological period has been as cold as our current geologic period, the Quaternary, for at least 250 million years.
This graph, though, also includes expected warming from our CO2 emissions and suggests we're causing a transition from ice house to hothouse conditions. Scotese says,
Nature may not have its way. Things have changed. We have changed things. The addition of CO2 to the atmosphere during the last 200 years of human history has amplified this natural warming trend and the average global temperature has risen rapidly. The average global temperature was 12˚C during the Last Glacial Maximum (21,0000 years ago). During the following Interglacial period, the average global temperature slowly rose to 13.8˚C. Since 1880, it has increased another .6˚ degrees to 14.4˚C (as of 2015). This rate of warming is ~50 times faster than the rate of warming during the previous 21,000 years.
As shown in the graph above, Scotese' estimate of Post-‐Anthropogenic Warming (PAW) is 19.8˚C. The instrumental record currently shows that the last 5 years have averaged 1.2 C warmer than the 1850-1900 mean, so his 0.6˚C estimate for 2015 above 1880 is probably not fully accurate (he needs error bars!), but what should be clear here is that Scotese is not a friend of Wrightstone's interpretation of Scotese's schematic. Geologic history tells us that current warming is exceptional; and while it's obviously been warmer in the past, it has not been warmer on earth when we were living on it with coastal cities and other infrastructures of civilization that depend on a relatively stable climate like humanity enjoyed during the Holocene. The issue is not how hot it's been in the past; the issue is how rapidly we're making the earth hotter now.
Conclusion
The third chapter of Mr. Wrightstone's self-published book continues to misinform in a manner very similar to the tradition he established in the first two chapters. He misrepresents and rejects the proxy evidence we have that conclusively documents the extraordinary warming we've experienced since the industrial revolution. He consistently confuses local and global temperatures, even when he has access to global temperature data that he could have used. And many of his claims and arguments are nothing short of incompetent.
As I've pointed out before, I'm just a guy who likes to read science. I'm not an expert. I try to document everything I say so that you can check up on me. So please consult the references below. I've also written on numerous points related to Mr. Wrightstone's misinformation in other posts, and I've linked to those posts. There are other resources in the references to those posts that you can use as well. But Mr. Wrightstone presents himself as somewhat of an "expert" on climate science. He claims to be presenting "facts" that people like Al Gore don't want you to know. But what we can clearly see here is that Mr. Wrightstone's book is extremely short on presenting facts that actually undermine anything in climate science. The facts in this book are contorted and twisted to say what they simply don't mean, and they're combined with incompetence, misinformation, and falsehoods to further distort the actual evidence we have about global temperatures and how they have increased above preindustrial levels.
References:
[1] Wrightstone, Gregory. INCONVENIENT FACTS: The science that Al Gore doesn't want you to know. Mill City Press. Kindle Edition.
[2] Mann, M., Bradley, R. & Hughes, M. Global-scale temperature patterns and climate forcing over the past six centuries. Nature 392, 779–787 (1998). https://doi.org/10.1038/33859 and[3 ] Mann, M. E., Bradley, R. S., & Hughes, M. K. (1999). Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters, 26(6), 759–762. doi:10.1029/1999gl900070
[4] https://citizenschallenge.blogspot.com/2013/07/revealed-dr-manns-letter-to-rep-joe.html?fbclid=IwAR14xfqOVugwsyg8rfU6k-KHjsRSXzS9VX2Bwhjub8K9yFPkjYhUzdV_yZk
[5] Rutherford, S., M. E. Mann, T. J. Osborn, K. R. Briffa, P. Jones, R. S. Bradley, and M. K. Hughes, 2005: Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Method, Predictor Network, Target Season, and Target Domain. J. Climate, 18, 2308–2329, https://doi.org/10.1175/JCLI3351.1.
[6] Wahl, E.R., Ammann, C.M. Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence. Climatic Change 85, 33–69 (2007). https://doi.org/10.1007/s10584-006-9105-7
[7] Mann ME, Zhang Z, Hughes MK, Bradley RS, Miller SK, Rutherford S, and Ni F: Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. Proceedings of the National Academy of Sciences, 105(36):13252–13257, 2008. dx.doi.org/10.1073/pnas.0805721105. https://www.pnas.org/content/105/36/13252
[8] Hockey Stick Papers: https://gist.github.com/priscian/81099e9332c86800d538542fb7027eaf?fbclid=IwAR02HjrebPwdQ7fWCGrG8RndoShrxA9p5RrzzPUmT3v_zAOpDmuYXuI308c
[9] PAGES 2k Consortium: Continental-scale temperature variability during the past two millennia. Nat Geosci 6(5):339–346, 2013. dx.doi.org/10.1038/ngeo1797.
[10] Emile-Geay, J., McKay, N., Kaufman, D. et al. A global multiproxy database for temperature reconstructions of the Common Era. Sci Data 4, 170088 (2017). https://doi.org/10.1038/sdata.2017.88
[5] Rutherford, S., M. E. Mann, T. J. Osborn, K. R. Briffa, P. Jones, R. S. Bradley, and M. K. Hughes, 2005: Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Method, Predictor Network, Target Season, and Target Domain. J. Climate, 18, 2308–2329, https://doi.org/10.1175/JCLI3351.1.
[6] Wahl, E.R., Ammann, C.M. Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence. Climatic Change 85, 33–69 (2007). https://doi.org/10.1007/s10584-006-9105-7
[7] Mann ME, Zhang Z, Hughes MK, Bradley RS, Miller SK, Rutherford S, and Ni F: Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. Proceedings of the National Academy of Sciences, 105(36):13252–13257, 2008. dx.doi.org/10.1073/pnas.0805721105. https://www.pnas.org/content/105/36/13252
[8] Hockey Stick Papers: https://gist.github.com/priscian/81099e9332c86800d538542fb7027eaf?fbclid=IwAR02HjrebPwdQ7fWCGrG8RndoShrxA9p5RrzzPUmT3v_zAOpDmuYXuI308c
[9] PAGES 2k Consortium: Continental-scale temperature variability during the past two millennia. Nat Geosci 6(5):339–346, 2013. dx.doi.org/10.1038/ngeo1797.
[10] Emile-Geay, J., McKay, N., Kaufman, D. et al. A global multiproxy database for temperature reconstructions of the Common Era. Sci Data 4, 170088 (2017). https://doi.org/10.1038/sdata.2017.88
[11] Christopher R. Scotese, Haijun Song, Benjamin J.W. Mills, Douwe G. van der Meer,
Phanerozoic paleotemperatures: The earth’s changing climate during the last 540 million years,
Earth-Science Reviews,Volume 215 (2021):103503. https://doi.org/10.1016/j.earscirev.2021.103503.
[12] Scotese, Christopher. (2016). Some Thoughts on Global Climate Change: The Transition for Icehouse to Hothouse Conditions.
https://www.researchgate.net/publication/275277369_Some_Thoughts_on_Global_Climate_Change_The_Transition_for_Icehouse_to_Hothouse_Conditions
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