Hockey Sticks in the scientific literature

The "hockey stick" is the famous reconstruction of past temperatures originally found by Mann, Bradley and Hughes in their 1998 paper, and extended in their 1999 paper.

Since those two publications, many other researchers have found similar results, either for the globe as a whole (like PAGES 2k), or a hemisphere, or regionally. And others have extended them further back in the past, also finding a hockey stick graph.

This isn't especially surprising, as I showed here and here -- a hockey stick is expected from the basic laws of physics. In fact, it'd be far more surprising if global reconstructions didn't find a hockey stick.


Here are comparisons of reconstructions of the last 1,000 years, from Skeptical Science:


Below is a list of some of the papers that have found hockey sticks. Many of these, and their descriptions, were compiled by Jim Milks of Seeing the Environment Forest. See his post for links to each study if they’d not included here. I’ve added several new papers at the bottom.

If you know of others, or have suggestions or criticisms, please email me here.


“Global-scale temperature patterns and climate forcing over the past six centuries,” Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes, Nature 392, 779-787 (23 April 1998).


“Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations,” Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes, Geophysical Research Letters, Volume 26, Issue 6, 15 March 1999, pp 759–762


“Causes of Climate Change Over the Past 1000 Years,” Thomas J. Crowley, Science 14 Jul 2000, v289 issue 5477 pp. 270-277: 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.

“Temperature trends over the past five centuries reconstructed from borehole temperatures,” Huang, et al. Nature 403, 756-758(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.


A Bayesian algorithm for reconstructing climate anomalies in space and time. Part I: Development and applications to paleoclimate reconstruction problems, MP Tingley and P Huybers, Journal of Climate 23 (2010), 2759-2781.

A Bayesian algorithm for reconstructing climate anomalies in space and time. Part II: Comparison with the regularized expectation-maximization algorithm, MP Tingley, and P Huybers, Journal of Climate 23 (2010), 2782-2800.

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.

A New Reconstruction of Temperature Variability in the Extra-Tropical Northern Hemisphere During the Last Two Millennia, F.C. Ljungqvist, Geografiska Annaler, Volume 92, Issue 3, September 2010, pages 339–351: 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.

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.

“A Reconstruction of Regional and Global Temperature for the Past 11,300 Years,” Marcott et al, Science v339 n6124 pp 1198-1201, March 8, 2013: Reconstructed global temperatures over the past 11,000 years using sediment cores. Data ended at AD 1940.

"Continental-scale temperature variability during the past two millennia," PAGES 2k Consortium, Nature Geosciences, April 21, 2013: Used multiple proxies (tree rings, sediment cores, ice cores, stalagmites, pollen, etc) to reconstruct regional and global temperatures since AD 1.

"Pairwise comparisons to reconstruct mean temperature in the Arctic Atlantic Region over the last 2,000 years," Sami Hanhijarvi, et al, Clim Dyn (2013).

“Used proxy and instrumental records to reconstruct global temperatures from AD 1753 to AD 2011,” Rohde et al, Geoinfor Geostat: An Overview (2013), 1:1.

"Millennial minimum temperature variations in the Qilian Mountains, China: evidence from tree rings," Y. Zhang eet al, Climate of the Past (2014), 10, 1763–1778, 2014.

"A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium," Shi et al, Climate Change, August 2015, Volume 131, Issue 4, pp 663-676.

"Heterogeneous warming of Northern Hemisphere surface temperatures over the last 1200 years," Martin P. Tingley and Peter Huybers, Journal of Geophysical Research: Atmospheres, Volume 120, Issue 9, Article first published online: 14 May 2015.

"Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long term context," Rob Wilson et al, Quaternary Science Reviews (2016) 134 1-18.


“Australasian Temperature Reconstructions Spanning the Last Millennium,” Gergis et al, Journal of Climate (2016) v29 n15 5365-5392. (Discussion)


“A global multiproxy database for temperature reconstructions of the Common Era,” PAGES 2k Consortium, Scientific Data volume 4, Article number: 170088 (11 July 2017).


“Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era,” PAGES 2k Consortium, Nature Geoscience, July 24, 2019.

·       Here’s their graph.


“Holocene global mean surface temperature, a multi-method reconstruction approach,” Darrell Kaufman et al, Scientific Data 7, Article Number: 201 (2020).


“Globally resolved surface temperatures since the Last Glacial Maximum,” Matthew B. Osman et al, Nature v 599 pp 239–244 (2021).

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Last updated 2/25/22