Sunday, October 27, 2013

Enough hockey sticks for a team

One of the persistent denier myths is that the Hockey Stick (usually meaning Mann et al. 1999) has been discredited.  Not only is that myth false but Mann et al. (1999) has been validated through the publication of numerous hockey stick graphs since 1999.  Here is a brief list of the ones I know:

Crowley 2000: Used both his own and Mann et al. (1999)'s hockey sticks to examine the cause of temperature changes over the past 1,000 years.  Found that natural forcings could not explain twentieth century warming without the effect of greenhouse gases.

Huang, et al. 2000: Reconstructed global average temperatures since AD 1500 using temperature data from 616 boreholes from around the globe.

Bertrand et al. 2002: Reconstructed solar output, volcanic activity, land use changes, and greenhouse gas concentrations since AD 1000, then computed the expected temperature changes due to those forcings.  Compared the computed temperature changes with two independent temperature reconstructions.

Esper et al. 2002: Reconstructed Northern Hemisphere temperatures between AD 800 and AD 2000 using tree ring chronologies.

Cronin et al. 2003: Reconstructed temperatures between 200 BC and AD 2000 around Chesapeake Bay, USA, using sediment core records.

Pollack and Smerdon 2004: Reconstructed global average temperatures since AD 1500 using temperature data from 695 boreholes from around the globe.

Esper et al. 2005: Compared and averaged five independent reconstructions of Northern Hemisphere temperatures from AD 1000 to AD 2000.

Moberg et al. 2005: Combined tree ring proxies with glacial ice cores, stalagmite, and lake sediment proxies to reconstruct Northern Hemisphere temperatures from AD 1 to AD 2000.

Oerlemans 2005: Reconstructed global temperatures from AD 1500 to AD 2000 using 169 glacial ice proxies from around the globe.

Rutherford, et al. 2005: Compared two multi-proxy temperature reconstructions and tested the results of each reconstruction for sensitivity to type of statistics used, proxy characteristics, seasonal variation, and geographic location.  Concluded that the reconstructions were robust to various sources of error.

D'Arrigo et al. 2006: Reconstructed Northern Hemisphere temperatures between AD 700 and AD 2000 from multiple tree ring proxies using a new statistical technique called Regional Curve Standardization.  Concluded that their new technique was superior to the older technique used by previous reconstructions.

Osborn and Briffa 2006: Used 14 regional temperature reconstructions between AD 800 and AD 2000 to compare spatial extent of changes in Northern Hemisphere temperatures.  Found that twentieth century warming was more widespread than any other temperature change of the past 1,200 years.

Hegerl et al. 2007: Combined borehole temperatures and tree ring proxies to reconstruct Northern Hemisphere temperatures over the past 1,450 years.  Introduced a new calibration technique between proxy temperatures and instrumental temperatures.

Juckes et al. 2007: Combined multiple older reconstructions into a meta-analysis.  Also used existing proxies to calculate a new Northern Hemisphere temperature reconstruction.

Wahl and Ammann 2007: Used the tree ring proxies, glacial proxies, and borehole proxies used by Mann et al. (1998, 1999) to recalculate Northern Hemisphere temperatures since AD 800.  Refuted the McIntyre and McKitrick criticisms and showed that those criticisms were based on flawed statistical techniques.

Wilson, et al. 2007: Reconstructed Northern Hemisphere temperatures from AD 1750 to AD 2000 using tree ring proxies that did not show a divergence problem after AD 1960.

Mann et al. 2008:  Reconstructed global temperatures between AD 200 and AD 2000 using 1,209 independent proxies ranging from tree rings to boreholes to sediment cores to stalagmite cores to Greenland and Antarctic ice cores.

Kaufman, et al. 2009: Used tree rings, lake sediment cores, and glacial ice cores to reconstruct Arctic temperatures between 1 BC and 2000 AD.

von Storch et al. 2009: Tested three different temperature reconstruction techniques to show that the Composite plus Scaling method was better than the other two methods.

Frank et al. 2010: A brief history of proxy temperature reconstructions, as well as analysis of the main questions remaining in temperature reconstructions.

Kellerhals et al. 2010: Used ammonium concentration in a glacial ice core to reconstruct tropical South American temperatures over the past 1,600 years.

Ljungqvist 2010: Reconstructed extra-tropical Northern Hemisphere temperatures from AD 1 to AD 2000 using historical records, sediment cores, tree rings, and stalagmites.

Thibodeau et al. 2010: Reconstructed temperatures at the bottom of the Gulf of St. Lawrence since AD 1000 via sediment cores.

Tingley and Huybers 2010a, 2010b: Used a Bayesian approach to reconstruct North American temperatures.

Büntgen et al. 2011:  Used tree ring proxies to reconstruct Central European temperatures between 500 BC and AD 2000.

Kemp et al. 2011: Reconstructed sea levels off North Carolina, USA from 100 BC to AD 2000 using sediment cores.  They also showed that sea levels changed with global temperature for at least the past millennium.

Kinnard et al. 2011: Used multiple proxies to reconstruct late summer Arctic sea ice between AD 561 and AD 1995, using instrumental data to extend their record to AD 2000.

Martin-Chivelet et al. 2011: Reconstructed temperatures in the Iberian Peninsula from 2000 BC to AD 2000 using stalagmites.

Spielhagen et al. 2011: Reconstructed marine temperatures in the Fram Strait from 100 BC to AD 2000 using sediment cores.

Esper et al. 2012: Used tree ring proxies to reconstruct Northern Scandinavian temperatures 100 BC to AD 2000.  May have solved the post-AD 1960 tree ring divergence problem.

Ljungqvist et al. 2012: Used a network of 120 tree ring proxies, ice core proxies, pollen records, sediment cores, and historical documents to reconstruct Northern Hemisphere temperatures between AD 800 and AD 2000, with emphasis on proxies recording the Medieval Warm Period.

Melvin et al. 2012: Reanalyzed tree ring data for the Torneträsk region of northern Sweden.

Abram et al. 2013: Reconstructed snow melt records and temperatures in the Antarctic Peninsula since AD 1000 using ice core records.

Marcott, et al. 2013: Reconstructed global temperatures over the past 11,000 years using sediment cores.  Data ended at AD 1940.

PAGES 2k Consortium 2013: Used multiple proxies (tree rings, sediment cores, ice cores, stalagmites, pollen, etc) to reconstruct regional and global temperatures since AD 1.

Rhodes et al. 2013: Used proxy and instrumental records to reconstruct global temperatures from AD 1753 to AD 2011.

The proper response to someone who asserts that the Hockey Stick has been falsified is to ask "Which one?"  As for what most of the temperature reconstructions show, the data from Marcott et al. (2013) combined with 30-year smoothed HadCRUT4 data is fairly representative:

Update:  I've posted two lengthy responses rebutting "Anonymous" in the comments.  Quite frankly, none of "his" numerous claims stand up to scrutiny.  Part 1, Part 2.


  1. Very nice. The commentary really helps.

    If someone takes the holocene CO2 record, would not that also be a hockey stick?

    How about the Arctic summer ice extent spiraling down. That sure looks like another hockey stick.

    1. Both of those are good examples of hockey sticks. Thanks for reminding me of Kinnard et al. (2011), as they showed the extent to which Arctic sea ice minimums had changed over the past 1,450 years.

  2. As a paleogeneticist, I must use climate models. This means that I understand their defects.
    Mann's "hockey stick" had two features that, when it emerged, astonished all of us in the science in two respects:
    (a) The "Little Ice Age" was not recorded in the proxies that Mann used. And yet this climate phenomenon was well documented.
    (b) The statement that this was the "warmest year on record", when we all knew the evidence that the Medieval warm period was as warm as today, the Minoan and Roman warm periods were warmer, and earlier periods were MUCH warmer (we just got fossil human footprints in England ~750,000 years ago). And yet the methane did not come out off the permafrost and the climate did not "run away".
    In both respects, Mann's hockey stick was wrong. Further, we know WHY it was wrong. We know the statistical mistakes that he made. We know the data that he chose to not include. We know that his proxies do not track the record in the last 30 years.
    Now, we have articles like this, claiming that recent work validates the "hockey stick". All while putting in9 figures do NOT show a hockey stick. Rather than showing the flat temperature during the Medieval warm period, the Medieval warm period is back.
    And they continue to use Mann's "trick", splicing (questionable) thermometer data (the blue) to the proxy data. Which is simply unacceptable practice.
    Those of us who are actually scientists marvel at the inability of lay people to see what is before their eyes. There is no hockey stick in the figure. The proxy-estimated temperature was much warmer on the 10000 year time scale, rises in the Medieval, falls in the Little Ice Age, and recovered well before human emission of CO2, There ... is ... no ... hockey... stick. Yet Jim Milks thinks he sees "hockey sticks".
    The only thing left is the illusion that we warmer today than in the post-glacial, Minoan, Roman, or Warm Periods. This illusion comes from splicing of different kinds of data with (as we know from the East Anglia emails) was a deliberate effort to deceive.Those intent to believe in "hockey sticks" are, of course, uneducable. However, with footprints of hominids padding around England, which then had a Mediterranean-type climate, it is clear that as a matter of fact,the Earth is NOT warmer today than them.

    1. You call yourself a paleogeneticist, portray yourself as an "expert" but then display striking ignorance about the various papers that have been published in the 14+ years since the original Mann et al. publication as well as a penchant for repeatedly debunked conspiracy theories. Hint: Climategate was investigated 11 times and debunked by every single investigation. Go read the papers I cited, as you're functionally illiterate in your claimed field of expertise. Your comment reeks more of Watts Up With That than it does any actual scientific knowledge.

    2. I have read the papers. I coauthored some of them. But even someone as hopelessly "ignorant" as you say that I am can look at MBH98 and see a flat line traversing the MWP, and (then) look that the papers that correct Mike's mistakes (including the plot that you reproduce above) and see the MWP. There ... Is .. No ... Hockey ... Stick.

      One needs to be a bit less ignorant to know that HADCRUT4 is direct temperature measurements, highly massaged. With the community quite divided as to whether they have been inappropriately massaged.

      And one does need to have science training to know that one is not allowed to splice together two kinds of data together and then draw conclusions as if they were one kind of data.

      The meaning for science? Well, for one thing, the fact that the historical past has had temperatures higher than today, and we did not see a "thermal runaway" due to any of the mechanisms presently feared (loss of albedo, outgassing of methane from the permafrost, ...) means that these need not be feared. Other mechanisms based on human generated CO2? Perhaps. But the primary greenhouse wavelengths are soon to be saturated, and the water vapor needed to carry the warming is not behaving as models suggest it should. Don't know why.

      What YOU should take away from this is an object lesson of how badly public policy is served when science is politicized and (therefore) corrupted. To have the Vice President (and, arguably, the man who was elected president in 2000) determine the "science" to be "settled" and to pick as his "winner" someone who cherry picks data to get his desired outcome (or, being charitable, cannot do statistics correctly) has created enormous dysfunction.

    3. Think you'll be interested in this article I wrote to deal with the Gish Gallop of BS you spewed in your first comment. It's pretty obvious that you have no actual expertise. Given what you spewed, I highly doubt that you're any sort of scientist at all.

    4. And here's my reply to your second comment:

      All you've shown here is that your claims about your background and knowledge are BS. Go back to WUWT or Forbes, where you can pass yourself off as a scientist, as you've no credibility here.

  3. JIm

    Have you seen this? You might add to the team

    1. Jack,

      Yes, I have read that one. That's the Pages 2k Consortium paper, which is the next to last paper on my list. I've altered the reference to make that clearer, as I had listed it as just "Pages 2k." The link I gave in the list is to the full pdf in case any readers cannot get through the Nature firewall.

      Thanks for reading and checking to keep me current.

  4. Jim. The Gergis et al 2012 paper in your list was/is withdrawn.

    1. Thanks. I've removed the link for now.

  5. Your anonymous paleogeneticist appears elsewhere on the web. Back in 2010 we find him at where he identifies himself as Steven Benner and makes many of the same lame claims.

    Of interest, Tony Heller appears as well.

    1. Good catch. Thanks. The Steven Benner I've heard of with is a molecular geneticist who pioneered synthetic biology. My hunch would be that the troll on was impersonating an actual scientist in hopes of gaining false credibility.

  6. Having used your list in the past.

    Hockey sticks in AR5? Yes.

    And some links may need updating. Two of your three jet stream sites are defunct. The third requires a password, etc.

  7. Thanks for the note. I've checked and updated all the links on my list. Unfortunately, it appears that the Kinnard et al. 2011 pdf link is no longer functional so I've reverted back to the link to the abstract. The rest have been updated as needed, as some pdfs are now publicly available whereas they were still behind paywalls when I wrote this post.