Michael E. Mann

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Michael E. Mann
Born 1965
Amherst, Massachusetts
Nationality American
Education A.B. applied mathematics and physics (1989), MS physics (1991), MPhil physics (1991), MPhil geology (1993), PhD geology & geophysics (1998)[1]
Alma mater University of California, Berkeley, Yale University
Occupation Climatologist
Employer Pennsylvania State University
Known for Temperature record of the past 1000 years
Hockey stick graph
Lead author on the IPCC Third Assessment Report
Awards Philip M. Orville Prize (1997)
NOAA Outstanding Scientific Publication (2002)
AAG John Russell Mather Paper of the Year (2006)
American Geophysical Union Fellow (2012)[2]
2012 Hans Oeschger Medal[1]
Website Mann's home page

Michael E. Mann (born 1965) is an American climatologist and geophysicist,[1] currently director of the Earth System Science Center at Pennsylvania State University, who has contributed to the scientific understanding of historic climate change based on the temperature record of the past thousand years. He has pioneered techniques to find patterns in past climate change, and to isolate climate signals from "noisy data".[3]

As lead author of a paper produced in 1998 with co-authors Raymond S. Bradley and Malcolm K. Hughes, Mann introduced innovative statistical techniques to find regional variations in a hemispherical climate reconstruction covering the past 600 years. In 1999 the same team used these techniques to produce a reconstruction over the past 1,000 years (MBH99) which was dubbed the "hockey stick graph" because of its shape. He was one of 8 lead authors of the "Observed Climate Variability and Change" chapter of the Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment Report published in 2001. A graph based on the MBH99 paper was highlighted in several parts of the report, and was given wide publicity. The IPCC acknowledged that his work, along with that of the many other lead authors and review editors, contributed to the award of the 2007 Nobel Peace Prize, which was won jointly by the IPCC and Al Gore.

He was organizing committee chair for the National Academy of Sciences Frontiers of Science in 2003 and has received a number of honors and awards including selection by Scientific American as one of the fifty leading visionaries in science and technology in 2002. In 2012 he was inducted as a Fellow of the American Geophysical Union and was awarded the Hans Oeschger Medal of the European Geosciences Union. In 2013 he was elected a Fellow of the American Meteorological Society, and awarded the status of distinguished professor in Penn State's College of Earth and Mineral Sciences.

Mann is author of more than 160 peer-reviewed and edited publications, and has published two books: Dire Predictions: Understanding Global Warming in 2008 and The Hockey Stick and the Climate Wars: Dispatches from the Front Lines, published in early 2012. In 2013 the European Geosciences Union described his publication record as "outstanding for a scientist of his relatively young age". He is also a co-founder and contributor to the climatology blog RealClimate.

Early life, undergraduate studies[edit]

Mann was born in 1965, and brought up in Amherst, Massachusetts, where his father was a professor of mathematics at the University of Massachusetts. At school he was interested in math, science, and computing. In 1983 he was prompted by seeing the film WarGames to write a rudimentary self-learning tic-tac-toe program which made random moves and listed losing moves which it would not repeat. Mann found a "trick" of using symmetry to reduce the number of unique moves to store so that the computer would not slow down so much.[4]

In August 1984 he went to the University of California, Berkeley, to major in physics with a second major in applied math. His second year research in the theoretical behaviour of liquid crystals used the Monte Carlo method applying randomness in computer simulations. Late in 1987 he joined a research team under Didier de Fontaine which was using similar Monte Carlo methodology to investigate the superconducting properties of yttrium barium copper oxide, modelling transitions between ordered and disordered phases.[5] He graduated with honors in 1989 with an A.B. in applied mathematics and physics.[1]

Doctoral and postgraduate studies[edit]

Mann then attended Yale University, intending to obtain a PhD in physics, and received both an MS and an MPhil in physics in 1991. His interest was in theoretical condensed matter physics but he found himself being pushed towards detailed semiconductor work. He looked at course options with a wider topic area, and was enthused by PhD adviser Barry Saltzman about climate modelling and research. To try this out he spent the summer of 1991 assisting a postdoctoral researcher in simulating the period of peak Cretaceous warmth when CO2 levels were high, but fossils indicated most warming at the poles, with little warming in the tropics. Mann then joined the Yale Department of Geology and Geophysics, obtaining an MPhil in geology and geophysics in 1993. His research focused on natural variability and climate oscillations. He worked with the seismologist Jeffrey Park, and their joint research adapted a statistical method developed for identifying seismological oscillations to find various periodicities in the instrumental temperature record, the longest being about 60 to 80 years. The paper Mann and Park published in December 1994 came to similar conclusions to a study developed in parallel using different methodology and published in January of that year, which found what was later called the Atlantic multidecadal oscillation.[6]

In 1994, Mann participated as a graduate student in the inaugural workshop of the National Center for Atmospheric Research's Geophysical Statistics Project aimed at encouraging active collaboration between statisticians, climatologists and atmospheric scientists. Leading statisticians participated, including Grace Wahba and Arthur P. Dempster.[7]

While still finishing his PhD research, Mann met UMass climate science professor Raymond S. Bradley and began research in collaboration with him and Park. Their research used paleoclimate proxy data from Bradley's previous work and methods Mann had developed with Park, to find oscillations in the longer proxy records. "Global Interdecadal and Century-Scale Climate Oscillations During the Past Five Centuries" was published by Nature in November 1995.[8]

Another study by Mann and Park raised a minor technical issue with a climate model about human influence on climate change: this was published in 1996. In the context of controversy over the IPCC Second Assessment Report the paper was praised by those opposed to action on climate change, and the conservative organisation Accuracy in Media claimed that it had not been publicised due to media bias. Mann defended his PhD thesis on A study of ocean-atmosphere interaction and low-frequency variability of the climate system in the spring of 1996,[9][10] and was awarded the Phillip M. Orville Prize for outstanding dissertation in the earth sciences in the following year. He was granted his PhD in geology and geophysics in 1998.[1]

Postdoctoral research: the hockey stick graph[edit]

Michael Mann speaking about "The Hockey Stick and the Climate Wars" at The Amaz!ng Meeting in Las Vegas, July 13, 2013

From 1996–1998, after defending his PhD thesis at Yale, Mann carried out paleoclimatology research at the University of Massachusetts Amherst funded by a United States Department of Energy postdoctoral fellowship. He collaborated with Raymond S. Bradley and Bradley's colleague Malcolm K. Hughes, a Professor of Dendrochronology at the University of Arizona, with the aim of developing and applying an improved statistical approach to climate proxy reconstructions. He taught a course in Data Analysis and Climate Change in 1997 and became a Research Assistant Professor the following year.[1][11]

The first truly quantitative reconstruction of Northern Hemisphere temperatures had been published in 1993 by Bradley and Phil Jones, but it and subsequent reconstructions compiled averages for decades, covering the whole hemisphere. Mann wanted temperatures of individual years showing differences between regions, to find spatial patterns showing natural oscillations and the effect of events such as volcanic eruptions. Sophisticated statistical methods had already been applied to dendroclimatology, but to get wider geographical coverage these tree ring records had to be related to sparser proxies such as ice cores, corals and lake sediments. To avoid giving too much weight to the more numerous tree data, Mann, Bradley and Hughes used the statistical procedure of principal component analysis to represent these larger datasets in terms of a small number of representative series and compare them to the sparser proxy records. The same procedure was also used to represent key information in the instrumental temperature record for comparison with the proxy series, enabling validation of the reconstruction. They chose the period 1902–1980 for calibration, leaving the previous 50 years of instrumental data for validation. This showed that the statistical reconstructions were only skillful (statistically meaningful) back to 1400.[12]

Their study highlighted interesting findings, such as confirming anecdotal evidence that there had been a strong El Niño in 1791, and finding that in 1816 the "Year Without a Summer" in Eurasia and much of North America had been offset by warmer than usual temperatures in Labrador and the Middle East. It was also an advance on earlier reconstructions in that it went back further, showed individual years, and showed uncertainty with error bars."[13] Global-scale temperature patterns and climate forcing over the past six centuries" (MBH98) was published on April 23, 1998 in the journal Nature. In it, "Spatially resolved global reconstructions of annual surface temperature patterns" were related to "changes in greenhouse-gas concentrations, solar irradiance, and volcanic aerosols" leading to the conclusion that "each of these factors has contributed to the climate variability of the past 400 years, with greenhouse gases emerging as the dominant forcing during the twentieth century. Northern Hemisphere mean annual temperatures for three of the past eight years are warmer than any other year since (at least) AD 1400.[14] The last point received most media attention. Mann was surprised by the extent of coverage which may have been due to chance release of the paper on Earth Day in an unusually warm year. In a CNN interview, John Roberts repeatedly asked him if it proved that humans were responsible for global warming, to which he would go no further than that it was "highly suggestive" of that inference.[15]

In May 1998, Jones, Briffa and colleagues published a reconstruction going back a thousand years, but not specifically estimating uncertainties. As Bradley recalls, Mann's initial reaction to the paper was "Look at this. This is rubbish. You can't do this. There isn't enough information. There's too much uncertainty." Bradley suggested using the MBH98 methodology to go further back. Within a few weeks, Mann responded that to his surprise, "There is a certain amount of skill. We can actually say something, although there are large uncertainties."[16][17] Mann carried out a series of statistical sensitivity tests on 24 long term datasets, in which he statistically "censored" each proxy in turn to see the effect its removal had on the result. He found that a dataset which would otherwise have been reliable diverged from 1800 until around 1900, suggesting that it had been affected for that time by the CO2 "fertilisation effect". Using this dataset corrected in comparisons with other tree series, their reconstruction passed the validation tests for the extended period, but they were cautious about the increased uncertainties involved.[18]

The Mann, Bradley and Hughes reconstruction covering 1,000 years (MBH99) was published by Geophysical Research Letters in March 1999 with the cautious title Northern Hemisphere temperatures during the past millennium: inferences, uncertainties, and limitations.[17][19] Mann said that "As you go back farther in time, the data becomes sketchier. One can't quite pin things down as well, but, our results do reveal that significant changes have occurred, and temperatures in the latter 20th century have been exceptionally warm compared to the preceding 900 years. Though substantial uncertainties exist in the estimates, these are nonetheless startling revelations."[20] When Mann gave a talk about the study to the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory, climatologist Jerry D. Mahlman nicknamed the graph the "hockey stick".[17]


University positions[edit]

In 1999, Mann secured a position as a tenure-track assistant professor in the Department of Environmental Sciences at the University of Virginia. He left Virginia in 2005 to become an associate professor in the Department of Meteorology (with joint appointments in Department of Geosciences and Earth and Environmental Systems Institute) at Pennsylvania State University, where he was also appointed the Director of its Earth System Science Center. He was promoted to full professor in 2009 and to "Distinguished Professor of Meteorology" in 2013.[1]

IPCC Third Assessment Report[edit]

Before the publication of MBH98, Mann had been nominated to be an author on the IPCC Third Assessment Report. Late in 1998 he heard that he had been selected as a lead author for the "observations" chapter of the Working Group I report. He was to work with the numerous contributing authors in preparing an assessment of the state of knowledge of the paleoclimate record, starting by soliciting input from the leading experts in that field.[21]

Mann was one of 8 lead authors of the "Observed Climate Variability and Change" chapter of the report, working under the two co-ordinating lead authors for the chapter. The report was published in 2001.[22]

Research in the 2000s[edit]

Mann continued his interest in improving methodology to find patterns in high-resolution paleoclimate reconstructions: he was lead author with Bradley and Hughes on a study of long term variability in the El Niño southern oscillations and related teleconnections, published in 2000.[23] His areas of research have included climate signal detection, attribution of climate change and coupled ocean-atmosphere modeling, developing and assessing methods of statistical and time series analysis and comparing the results of modelling against data.[1]

The original MBH98 and MBH99 papers avoided undue representation of large numbers of tree ring proxies by using a principal component analysis step to summarise these proxy networks, but from 2001 Mann stopped using this method and introduced a multivariate Climate Field Reconstruction (CFR) technique using a regularized expectation–maximization (RegEM) method which did not require this PCA step. In May 2002 Mann and Scott Rutherford published a paper on testing methods of climate reconstruction which discussed this technique. By adding artificial noise to actual temperature records or to model simulations they produced synthetic datasets which they called "pseudoproxies". When the reconstruction procedure was used with these pseudoproxies, the result was then compared with the original record or simulation to see how closely it had been reconstructed.[24]

In August 2003 Mann with Phil Jones published reconstructions using various high-resolution proxies including tree rings, ice cores and sediments. This study indicated that that Northern Hemisphere late 20th century warmth had no precedent for roughly 2,000 years, dwarfing Medieval warmth, but proxy data was still too sparse to evaluate the Southern Hemisphere.[25]

More recently, Mann's areas of research have included hurricanes and climate change, and climate modeling.[26] His work using comparisons with the results of climate models indicated that cooling from large volcanoes was not fully shown by tree ring reconstructions, and suggested that in extreme cases cooling caused by eruptions could result in trees showing no growth, and hence no tree ring for that year. The result would be that tree ring reconstructions could understate climate variability, and there has been scientific debate about the methodology and validity of these findings.[27]

A paper published in April 2014 by Mann and co-authors set out a new method of defining the Atlantic Multidecadal Oscillation (AMO) in place of a problematic method based on detrending the climate signal. They found that in recent decades the AMO had been in a cooling phase, rather than a warming phase as researchers had thought. This cooling had contributed towards the recent Global warming hiatus in surface temperatures, and would change to enhanced surface warming in the next phase of the oscillation.[28]

Hockey stick controversy[edit]

Figures based on the northern hemisphere mean temperatures graph from MBH99 were prominently featured in the IPCC Third Assessment Report of 2001, and became the focus of controversy when some individuals and groups disputed the data and methodology of this reconstruction.[29]

The 2006 North Report published by the United States National Academy of Sciences endorsed the MBH studies with a few reservations. The principal component analysis methodology had a small tendency to bias results so was not recommended, but it had little influence on the final reconstructions, and other methods produced similar results.[30][31] Mann has said his findings have been "independently verified by independent teams using alternative methods and alternative data sources."[32] More than two dozen reconstructions, using various statistical methods and combinations of proxy records, support the broad consensus shown in the original hockey stick graph, with variations in how flat the pre-20th century "shaft" appears.[33][34]

CRU email controversy[edit]

In November 2009, hackers obtained a large number of emails exchanged among researchers at the Climatic Research Unit of the University of East Anglia and with other scientists, including Mann. The release of their correspondence on the Internet sparked the Climatic Research Unit email controversy, commonly known as 'Climategate',[35][36] in which extracts from emails were publicized to raise accusations against the scientists. A series of investigations cleared the scientists of wrongdoing. It was found that their critics, who made unsupported accusations of falsification and manipulation or destruction of data, were commonly mistaken about the scientific issues.[37][38]

Mann was specifically cleared by several inquiries. Pennsylvania State University (PSU) commissioned two reviews related to the emails and his research, which reported in February and July 2010. They cleared Mann of misconduct, stating there was no substance to the allegations, but criticized him for sharing unpublished manuscripts with third parties.[39][40]

The United States Environmental Protection Agency (EPA) gave detailed consideration to petitions with allegations against Mann from lobbyists including the Southeastern Legal Foundation, Peabody Energy, the Competitive Enterprise Institute, and the Ohio Coal Association: the EPA found their claims were not supported by the evidence.[37][41]

At the request of Senator Jim Inhofe, who has called the science of man-made climate change a hoax, the Inspector General of the United States Department of Commerce investigated the emails in relation to NOAA, and concluded that there was no evidence of inappropriate manipulation of data.[38][42] The Office of the Inspector General (OIG) of the National Science Foundation also carried out a detailed investigation, which it closed on August 15, 2011. It agreed with the conclusions of the university inquiries, and exonerated Mann of charges of scientific misconduct.[38][43][44]

Attorney General of Virginia's investigative demand[edit]

Based on the CRU email leak, Virginia Attorney General Ken Cuccinelli initiated a Civil Investigative Demand against the University of Virginia to obtain documentation relating to Mann's work at the university. The demand sparked widespread academic condemnation as a "blatantly political" attempt to intimidate and silence Mann,[45] and was denied in August 2010 by a judge for failure to state sufficient cause.[46][47] Cuccinelli tried to re-open his case by issuing a revised subpoena,[48] and appealed the case to the Virginia Supreme Court. The case was defended by the university, and the court ruled that Cuccinelli did not have the authority to make these demands. The decision, seen as supporting academic freedom, was welcomed by the Union of Concerned Scientists.[49]

In October 2010, Mann wrote an op-ed in the Washington Post in which he described several past, present and projected attacks on climate science and scientists by politicians, drawing a link between them and "the pseudo-science that questioned the link between smoking cigarettes and lung cancer, and the false claims questioning the science of acid rain and the hole in the ozone layer." Saying they were "not good-faith questioning of scientific research [but] anti-science", he called for all his fellow scientists to stand against the attacks.[50]

In July 2013 Mann joined in the Terry McAuliffe gubernatorial campaign, 2013, promoting the role of scientific research and technology in job creation. Cuccinelli was the Republican candidate.[51] Mann highlighted the costs of the Civil Investigative Demand case, and the threat it had presented to the scientific community.[52]

Defamation lawsuit[edit]

Attacks on the work and reputation of climatologists continued, and Mann discussed with colleagues the need for a strong response when they were slandered or libeled. In July 2012,[53] Competitive Enterprise Institute (CEI) blogger Rand Simberg accused Mann of "deception" and "engaging in data manipulation" and alleged that the Penn State investigation that had cleared Mann was a "cover-up and whitewash" comparable to the recent Jerry Sandusky sex scandal, "except that instead of molesting children, he has molested and tortured data." The CEI blog editor then removed the sentence as "inappropriate", but a National Review blog post by Mark Steyn cited it and alleged that Mann's hockey stick graph was "fraudulent".[54][55]

Mann asked CEI and National Review to remove the allegations and apologize, or he would take action.[53] The CEI published further insults, and National Review editor Rich Lowry responded in an article headed "Get Lost" with a declaration that, should Mann sue, the discovery process would be used to reveal and publish Mann's emails. Mann's lawyer filed the defamation lawsuit in October 2012.[54]

Before the case could go to discovery, CEI and National Review filed a court motion to dismiss it under anti-SLAPP legislation, with the claim that they had merely been using exaggerated language which was acceptable against a public figure. In July 2013 the judge ruled against this motion,[56][57] and when the defendants took this to appeal a new judge also denied their motion to dismiss, in January 2014. The National Review changed its lawyers, and Steyn decided to represent himself in court.[53][58] Journalist Seth Shulman, at the Union of Concerned Scientists, welcomed the judge's statement that accusations of fraud "go to the heart of scientific integrity. They can be proven true or false. If false, they are defamatory. If made with actual malice, they are actionable."[59]

The defendants again appealed against the decision, and on 11 August 2014 the Reporters Committee for Freedom of the Press with 26 other organisations filed an amicus brief arguing that the comments at issue were constitutionally protected as opinion.[60][61] Steyn chose to be represented by attorney Daniel J. Kornstein.[62]


Mann's dissertation was awarded the Phillip M. Orville Prize in 1997 as an "outstanding dissertation in the earth sciences" at Yale University. His co-authorship of a scientific paper published by Nature won him an award from the Institute for Scientific Information (ISI) in 2002, and another co-authored paper published in the same year won the NOAA's outstanding scientific publication award. He was named by Scientific American as one of fifty "leading visionaries in science and technology." The Association of American Geographers awarded him the John Russell Mather Paper of the Year award in 2005 for a co-authored paper published in the Journal of Climate. The American Geophysical Union awarded him its Editors' Citation for Excellence in Refereeing in 2006 to recognize his contributions in reviewing manuscripts for its Geophysical Research Letters journal.[63]

The IPCC presented Mann, along with all other "scientists that had contributed substantially to the preparation of IPCC reports", with a personalized certificate "for contributing to the award of the Nobel Peace Prize for 2007 to the IPCC", celebrating the joint award of the 2007 Nobel Peace Prize to the IPCC and to Al Gore.[64][65][66][67]

In 2012, he was elected a Fellow of the American Geophysical Union[2] and awarded the Hans Oeschger Medal of the European Geosciences Union for "his significant contributions to understanding decadal-centennial scale climate change over the last two millennia and for pioneering techniques to synthesize patterns and northern hemispheric time series of past climate using proxy data reconstructions."[3][63]

Following election by the American Meteorological Society he became a new Fellow of the society in 2013.[68] In January 2013 he was designated with the status of distinguished professor in Penn State's College of Earth and Mineral Sciences.[69]

In September 2013, Mann was named by Bloomberg Markets in its third annual list of the "50 Most Influential" people, included in a group of "thinkers" with reference to his work with other scientists on the hockey stick graph, his responses on the RealClimate blog "to climate change deniers", and his book publications.[70][71] Later that month, he received the National Wildlife Federation's National Conservation Achievement Award for Science.[72]

On 28 April 2014 the National Center for Science Education announced that its first annual Friend of the Planet award had been presented to Mann and Richard Alley.[73]

Public outreach[edit]

Mann, along with Gavin Schmidt, Stefan Rahmstorf, and others, co-founded the RealClimate website, launched in December 2004. The website's purpose is to provide a site for commentaries by working climate scientists, "for interested public and journalists". It is part of The Guardian's Environmental Network.[74]

After repeated attacks against his and his colleagues' academic work and being "hounded by elected officials, threatened with violence, and more", Mann decided to "enter the fray" and "speak out about the very real implications of our research."[75] Mann has engaged with the public through film, television, radio, the press, and talks.[76] The Patriot-News reported in 2014, "The professor operates active Twitter and Facebook accounts. In several weeks, he'll take part in an "Ask Me Anything" session on Reddit. For him, it's about engaging with the community."[77]


Mann has been organizing committee chair for the National Academy of Sciences 'Frontiers of Science' and has served as a committee member or advisor for other National Academy of Sciences panels. He served as editor for the Journal of Climate and has been a member of numerous international and U.S. scientific advisory panels and steering groups. He is the lead author or co-author of over 90 scientific publications, the majority of which have appeared in leading peer-reviewed scientific journals.[39] Between 1999 and 2010 he served as principal or co-principal investigator on five research projects funded by the National Oceanic and Atmospheric Administration (NOAA) and four more funded by the National Science Foundation (NSF). He was also co-investigator on other projects funded by the NOAA, NSF, Department of Energy, United States Agency for International Development, and the Office of Naval Research.[39]

Selected publications[edit]


Selected editorials and opinion articles[edit]


  1. ^ a b c d e f g h Mann, Michael E. (2013). "Curriculum Vitae". Penn State, Dept. of Meteorology. Retrieved 11 January 2014. 
  2. ^ a b "Fellows Search Results". American Geophysical Union. Retrieved October 25, 2012. 
  3. ^ a b "EGU - Awards & Medals - Hans Oeschger Medal - Michael Mann". European Geosciences Union. 2012. Retrieved 19 September 2013. 
  4. ^ Mann 2012, pp. iv, 5–10
  5. ^ Mann 2012, pp. 5–6
  6. ^ Mann 2012, pp. 1–2, 6–10, 28–30
    Mann, M.E.; Park, J. (1994). "Global scale modes of surface temperature variability on interannual to century time scales" (PDF). Journal of Geophysical Research 99: 25819–25833. doi:10.1029/94JD02396. 
    Schlesinger, M. E.; Ramankutty, N. (1994). "An oscillation in the global climate system of period 65–70 years". Nature 367 (6465): 723. doi:10.1038/367723a0. 
  7. ^ House Committee on Energy and Commerce (2006). "Questions surrounding the 'Hockey stick' temperature studes; implications for climate change assessments". Hearings before the Subcommittee on Oversight and Investigations of the Committee on Energy and Commerce, 109th Congress, Second session. U.S. Government Printing Office. pp. 765–766. Retrieved 2010-08-01  (PDF).
  8. ^ Mann 2012, pp. 30–34
    Mann, Michael E.; Park, Jeffrey; Bradley, R. S. (1995). "Global interdecadal and century-scale climate oscillations during the past five centuries". Nature 378 (6554): 266–270. Bibcode:1995Natur.378..266M. doi:10.1038/378266a0. 
  9. ^ "A study of ocean-atmosphere interaction and low-frequency variability of the climate system". Yale University. 1998. Retrieved 2012-08-04. 
  10. ^ Mann 2012, pp. 1–2, 41, 265–266
  11. ^ Mann 2012, pp. 41–42
  12. ^ Mann 2012, pp. 40–48
  13. ^ Mann 2012, p. 48
  14. ^ Mann, M. E.; Bradley, R. S.; Hughes, M. K. (1998). "Global-scale temperature patterns and climate forcing over the past six centuries". Nature 392 (6678): 779–787. Bibcode:1998Natur.392..779M. doi:10.1038/33859. 
  15. ^ Mann 2012, pp. 48–50
  16. ^ Jones, P. D.; Briffa, K. R.; Barnett, T. P.; Tett, S. F. B. (1998). "High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with General Circulation Model control-run temperatures". The Holocene 8 (4): 455–471. doi:10.1191/095968398667194956. 
  17. ^ a b c Monastersky, Richard (September 8, 2006). "Climate Science on Trial - Research". The Chronicle of Higher Education. p. 10. Retrieved 2011-03-06. 
  18. ^ Mann 2012, pp. 50–53
  19. ^ 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. Bibcode:1999GeoRL..26..759M. doi:10.1029/1999GL900070. 
  20. ^ "News Releases : 1998 Was Warmest Year of Millennium, UMass Amherst Climate Researchers Report". UMass Amherst Office of News & Information. March 3, 1999. Retrieved 2011-03-06. 
  21. ^ Mann 2012, p. 53
  22. ^ Christy, J. R.; Clarke, R. A.; Gruza, G. V.; Jouzel, J.; Mann, M. E.; Oerlemans, J.; Salinger, M. J.; Wang, S.-W. (2001). "Observed Climate Variability and Change". Climate Change 2001: The Scientific Basis. Cambridge University Press. ISBN 0-521-80767-0. 
  23. ^ Mann, Bradley & Hughes 2000
  24. ^ Mann 2012, pp. 104–105, 306
  25. ^ Mann & Jones 2003.
  26. ^ Mann, Michael E. "Research Findings". Penn State University. Retrieved 1 October 2013. 
  27. ^ Johnson, Scott K. (4 February 2013). "Tree ring history spurs actual climate science debate". Ars Technica. Retrieved 1 October 2013. 
  28. ^ Messer, A'ndrea Elyse (7 April 2014). "Slowdown of global warming fleeting". Penn State University. Retrieved 28 April 2014. , Mann, M. E.; Steinman, B. A.; Miller, S. K. (2014). "On Forced Temperature Changes, Internal Variability and the AMO". Geophysical Research Letters: n/a. doi:10.1002/2014GL059233.  pdf
  29. ^ Pearce, Fred (February 9, 2010). "Part three: Hockey stick graph took pride of place in IPCC report, despite doubts | Environment". London: The Guardian. Retrieved 2010-03-08. 
  30. ^ Revkin, Andrew C. (22 June 2006), "Science Panel Backs Study on Warming Climate", New York Times 
    Committee on Surface Temperature Reconstructions for the Last 2,000 Years, National Research Council (2006). "Surface Temperature Reconstructions for the last 2,000 years". National Academies Press. 
  31. ^ Brumfiel, G. (June 2006). "Academy affirms hockey-stick graph". Nature 441 (7097): 1032–3. Bibcode:2006Natur.441.1032B. doi:10.1038/4411032a. PMID 16810211. 
  32. ^ Warner, Frank (2010-01-03). "Penn State climate professor: 'I'm a skeptic'". The Morning Call. Archived from the original on 2010-07-06. Retrieved 2010-07-06. And in a wide-ranging interview, Mann says that not all global warming science is settled. It's not yet certain, for example, that the heat is reducing the world population of polar bears or that it increases the number of hurricanes, he said. 
  33. ^ Frank, David; Esper, Jan; Zorita, Eduardo; Wilson, Rob (14 May 2010). "A noodle, hockey stick, and spaghetti plate: A perspective on high-resolution paleoclimatology". Wiley Interdisciplinary Reviews: Climate Change 1 (4): 507. doi:10.1002/wcc.53. 
  34. ^ Pearce, Fred (February 9, 2010). "Part four: Climate change debate overheated after sceptics grasped 'hockey stick' | Environment". London: The Guardian. Retrieved 2010-03-08. 
  35. ^ Douglas Fischer and The Daily Climate, "Climategate Scientist Cleared in Inquiry, Again," Scientific American, July 1, 2010. Retrieved 24 Aug. 2015.
  36. ^ Damian Carrington, "'Climategate' had only fleeting effect on global warming scepticism," The Guardian, 20 May 2014. Retrieved 24 Aug. 2015.
  37. ^ a b "Scientists' 'Climategate' e-mails 'just discussions'". BBC News. 6 August 2010. Retrieved 2 January 2014. 
  38. ^ a b c Efstathiou Jr., Jim (22 August 2011). "Climate-Change Scientist Cleared in Closing of U.S. Data-Altering Inquiry". Bloomberg. Retrieved 2 January 2014. 
  39. ^ a b c "Final Investigation Report Involving Dr. Michael E. Mann" (PDF). The Pennsylvania State University. June 4, 2010. Archived from the original (PDF) on 13 July 2010. 
  40. ^ Foley, Henry C.; Scaroni, Alan W.; Yekel, Candice A. (February 3, 2010). "RA-10 Inquiry Report: Concerning the Allegations of Research Misconduct Against Dr. Michael E. Mann, Department of Meteorology, College of Earth and Mineral Sciences, The Pennsylvania State University" (PDF). The Pennsylvania State University. Retrieved February 7, 2010.  The allegations were of "manipulating data, destroying records and colluding to hamper the progress of scientific discourse around the issue of anthropogenic global warming from approximately 1998."
  41. ^ "Denial of Petitions for Reconsideration of the Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act / Regulatory Initiatives / Climate Change / U.S. EPA". Environmental Protection Agency. 29 July 2010. Retrieved 16 September 2011. 
  42. ^ Zinser, Todd J., Inspector General of the U.S. Dept. of Commerce, in a letter to Sen. Inhofe, February 18, 2011, wrote, "We found no evidence in the CRU emails that NOAA inappropriately manipulated data comprising the GHCN-M dataset."
  43. ^ "Case Number: A09120086" (PDF). National Science Foundation Office of Inspector General. 
  44. ^ "Climate scientist cleared of research misconduct". physicsworld.com, A website from the Institute of Physics. August 30, 2011. Retrieved January 3, 2012. 
  45. ^ Walker, Julian (2010-05-19). "Academics fight Cuccinelli's call for climate-change records". The Virginian-Pilot. 
  46. ^ "A judge puts a damper on Mr. Cuccinelli's U-Va. witch hunt". Washington Post. August 31, 2010. 
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External links[edit]

External images
Michael Mann with tree rings