The Hockey Stick and the Climate Wars, by Michael E. Mann

“In this meticulous and engaging brief on climate change research and the political backlash to legitimate scientific work, Michael

Mann

With a postscript from the author updating the story and a new foreword from Bill Nye the Science Guy ©

Mann narrates the fight against misinformation from the inside.”

—Publishers Weekly

ment of corporate-funded chicanery demands a wide audience.”

“Confronting climate change will require clear scientific thinking and courageous action by many individuals. Mann’s book details the powerful evidence supporting climate change as well as the relentless attempts by climate change deniers to distort climate science and attack those who are speaking the truth about it.”

—Jerry Brown, Governor of California

“Mann’s honest and thorough testimony on the attacks against climate science is a critical step toward resolving the climate change debate.”

—Science

Michael E. Mann is Distinguished Professor of Meteorology and director of the Earth Systems Science Center at Penn State University. Despite being in the public eye, he continues an active research program in climate science and has published over 160 peer-reviewed papers in leading scientific journals. He is a fellow of the American Meteorological Society and the American Geophysical Union. In 2012 he received the Hans Oeschger Medal of the European Geosciences Union. Along with other scientists, he contributed to the reports of the IPCC, which was awarded a Nobel Peace Prize in 2007. He is also a co-founder of the award-winning website, RealClimate.org. $19.95 COLUMBIA UNIVERSITY PRESS ISBN: 978-0-231-15255-6 NEW YORK 51995 cup.columbia.edu 9 780231 152556

cover design: Milenda Nan Ok Lee

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the HOCKEY STICK CLIMATE WARS

—Kirkus Reviews (starred review)

AND THE

“An important and disturbing account of the fossil-fuel industry’s well-funded public relations campaign to sow doubt about the validity of the science of climate change. . . . This blistering indict-

the

hockey stick and the

climate wars DISPATCHES FROM THE FRONT LINES

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Michael E. Mann

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Postscript

The “hockey stick” graph has become a central figure in the debate over human-caused climate change. It tells a simple story: Earth’s temperature underwent only modest variations for much of the past millennium until spiking abruptly upward with the advent of industrialization and fossil fuel burning. Since the original publication of The Hockey Stick and the Climate Wars, there have been new developments in the science of paleoclimate reconstructions and in climate science more generally.

So too have there been renewed attacks on climate science and climate scientists by those who feel their vested interests threatened. Despite that, there seems to be growing recognition of the challenges we face as Earth continues to warm and how they might be met.

The Hockey Stick Lives On Though in the alternative universe of climate change denial the hockey stick has been thoroughly discredited, back in the real world, the opposite would seem to be true.1 Our key original findings have been validated again and again by several new studies. Among them was research showing the rapidity of the decline in Arctic sea ice in recent decades—a drop by nearly 50 percent since mid-twentieth century—to be unprecedented for at least a millennium and a half.2 The associated graph, displaying the slow drift upward in ice cover during the preceding fourteen centuries, followed by a precipitous drop over the past fifty

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years, resembles a hockey stick with its blade downturned—an “Arctic hockey stick.”

An “Antarctic hockey stick” emerged from yet another study. While a small uptick has occurred in the amount of sea ice surrounding Antarctica in recent decades—a phenomenon that was actually predicted by climate models as a result of warmer, moister air from the subtropics colliding with the frigid Antarctic winds—there has been a sharp loss of ice in the glaciers of the Antarctic Peninsula, one of the fastest warming regions in the world. The study, which analyzed ancient ice core evidence, found the recent glacial retreat to be unprecedented for at least the past millennium, with the rate of annual summer melt fluctuating modestly until the dawn of the Industrial Revolution, when it began to spike dramatically upward.3 This finding underscores evidence that the ice sheets in both Antarctica and Greenland appear to be losing ice earlier and faster than what climate models have projected. It serves as a reminder that, in many respects, existing climate model projections are proving to have been too conservative in what they portend for our future rather than, as critics like to claim, extremist and alarmist.

In April 2013 the PAGES 2K team, a group of 78 scientists from 60 institutions spanning 24 countries, released the most comprehensive estimate yet of global temperatures trends over past centuries.4 If our detractors were hoping the hockey stick might be “broken,” they were sadly disappointed. Th is study found the warmth of the past few decades to be higher than during any period in at least the past 1,400 years. The global temperature series they charted, in fact, was virtually indistinguishable5 from the original MBH99 hockey stick (see chapter 4).

But the analysis extended the original hockey stick conclusions in two important ways: the recent warming was established to be unprecedented over an even longer timeframe (1,400 rather than 1,000 years) and the conclusion applied to the entire globe, whereas the original hockey stick reflected only the Northern Hemisphere.

Yet another new study6 extended estimates of global temperature back even further—all the way to the end of the last ice age, a little more than 11,000 years ago. The conclusions were necessarily somewhat guarded as the authors employed more tenuous proxy data, such as ocean sediments, pollen deposits, and other records whose dating are hard to pinpoint with much accuracy and which tend to smooth out

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fluctuations. These factors make it very difficult to detect shorter-term temperature excursions. But even with these important caveats in mind, the study’s findings were profound. The abrupt warming spike of the past century appeared without precedent even back through the entire post-glacial period (the Holocene epoch). Indeed, since the conditions that prevailed during the last ice age are known to have been even colder, the modern warming spike is potentially unique in at least the past 125,000 years.7 The authors did find evidence for global temperatures that may have approached those of today during a mid-Holocene time interval centered around 7,000 years ago. That past warmth was attributed to slow changes in the geometry of Earth’s orbit around the Sun, which favored warmer summers and less snow and ice at that time. Some observers8 termed the new, longer curve “the scythe,” with its modest, broad warm peak centered 7,000 years ago and followed later by the sharp upward ramp of the past century. Measured against the scale of the projected 4–5°C warming by the end of the twenty-first century under businessas-usual fossil fuel emissions, the prehistoric peak all but disappears from view; the only clear feature that remains is the abrupt recent warming as it emerges from the barely perceptible (< 1°C) wiggles of the preindustrial period.9 At a time when carbon dioxide levels are flirting with the 400 parts per million (ppm) mark for the first time in millions of years,10 this latest study provides yet another vivid reminder of the unprecedented, uncontrolled experiment humanity is conducting with our climate. The lead author of the study, Shaun Marcott, is a young postdoctoral researcher, just as I was when we published our original hockey stick articles. Predictably, he and his coauthors were fiercely attacked by climate change deniers who tried, in vain, to discredit the work and the authors themselves.

The War on Science Continues Despite ever-increasing evidence of climate change and escalating levels of atmospheric greenhouse gases, the war on the science of climate change has continued unabated in America. Indeed, the assaults have grown uglier and more desperate—just what one expects to see in the dying days of an intellectually bankrupt campaign.