A pillar of the Kyoto Accord is based on flawed calculations, incorrect data
and an overtly biased selection of climate records, an important new paper reveals
Tim Patterson, Financial Post, October 29, 2003
This has been a nightmare of a year for aficionados of the Kyoto Accord. After
Canada's ratification of the treaty in late 2002, environmentalists had every
reason to believe that few climate experts would dare continue to publicly oppose
Kyoto's science, Russia would quickly ratify the accord and it soon would become
Instead, as illustrated at this month's World Climate Change Conference in Moscow, exactly the opposite has happened. The growing number of scientists who dispute the treaty's scientific foundation have become increasingly vocal, regularly pushing their case in the media as groundbreaking studies continue to be published that pull the rug out from under Kyoto's shaky edifice.
Of these, none may have the long-term impact of the paper published yesterday in the prestigious British journal Energy and Environment, which explains how one of the fundamental scientific pillars of the Kyoto Accord is based on flawed calculations, incorrect data and a biased selection of climate records.
The paper's authors, Toronto-based analyst Steve McIntyre and University of Guelph economics professor Ross McKitrick, obtained the original data used by Michael Mann of the University of Virginia to support the notion that the 20th-century temperature rise was unprecedented in the past millennium. A detailed audit revealed numerous errors in the data. After correcting these and updating the source records they showed that based on Mann's own methodologies, his original conclusion was flawed. Mann's original version resulted in the famous "hockey stick" graph that purported to show 900 years of relative temperature stability (the shaft of the hockey stick) followed by a sharp increase (the blade) in the 20th century (see graph). The corrected version of the last thousand years actually contradicts the view promoted by the Intergovernmental Panel on Climate Change (IPCC), and removes the foundation for claims of 20th-century uniqueness.
To understand the significance of the McIntyre/McKitrick announcement, it is important to consider how our understanding of long-term climate history has evolved over the past decade. In its 1990 and 1995 "Assessment Reports", the IPCC clearly identified two major global climatic events in the past millennium, as confirmed by thousands of papers written by quaternary geologists during the past century -- a "Medieval Warm Period" (MWP) from about 800 to 1300 A.D. that was as much as two degrees Celsius warmer than today, and a far colder "Little Ice Age" (LIA) from about 1300 to 1900 A.D. The effects of these events were felt worldwide with convincing evidence of both the MWP and LIA found in Europe, North America, Africa, the Caribbean, Peru and even in China, Japan and Australia. As part of our emergence from the LIA, scientists agreed there had been a gradual warming throughout the 20th century, although the reasons for this were hotly contested with increasing greenhouse gases (GHG) and changes in the output of the sun being leading contenders.
In recent years, however, the case for solar variations being the 20th century's major climate driver has become much stronger, much to the consternation of Kyoto supporters. After all, if long before human-induced GHG emission became significant, temperatures were considerably higher than today, there would be little reason to think today's temperatures were anything unnatural. This was especially true since long-term solar records indicated that both the MWP and LIA were closely correlated with changes in solar activity, and the output of the sun has indeed been increasing during the past century's 0.6C warming. Supporters of the GHG-induced warming hypothesis desperately needed a "smoking gun" to prop up the need for Kyoto.
This was conveniently supplied by Mann, Bradley and Hughes in their 1998 paper (referred to as "MBH98") in which they reduced the MWP and LIA to non-events outside Europe and unveiled their "hockey stick." The paper concluded, "Our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 the warmest year, at moderately high levels of confidence."
Of course, Kyoto fans were delighted. Despite being at odds with most of the scientific literature, and the fact that the MBH98 study was only one of thousands of possible millennial temperature constructions, advocates of the GHG hypothesis of climate change started to promote Mann's results as the definitive global temperature history. Within a year, with little real debate, the hockey stick became entrenched as the new orthodoxy, showing up in official documents everywhere.
However, the scientific review process that all studies must undergo before publication had failed in the case of the MBH98 paper. The temperature data before 1900 were not directly measured, as they were after 1900 when land-based thermometer readings were used. Instead, pre-1900 temperatures were calculated based on the measurement of "proxies," natural phenomena such as the growth of tree rings or coral that indicate what temperature was at certain times in the past. Consequently, grafting the two very different types of data sets together without significant overlap to come to dramatic conclusions was unwarranted and should have been seriously contested by the paper's reviewers. Chris de Freitas of the School of Geography and Environmental Science at the University of Auckland, New Zealand, sums up, "The Mann 'hockey stick' is nothing more than a mathematical construct vigorously promoted in the IPCC's 2001 report to affirm the notion that temperature changes of the 20th century were unprecedented."
Willie Soon and Sallie Baliunas of the Harvard Institute of Astrophysics added to the critique of Mann's hockey stick in March of this year when they showed that a careful analysis of 240 proxy studies reaffirmed that the MWP and the LIA were indeed worldwide phenomena, not limited to the European and North American continents. Baliunas and Soon's results coupled with this week's McIntyre/McKitrick paper may now end the debate for good. By looking carefully at the MBH98 data and their computational methods, McIntyre and McKitrick uncovered such serious flaws that the temperature indexes computed from it are, to quote McIntyre and McKitrick, "unreliable and cannot be used for comparisons between the current climate and that of previous centuries." Mann's claims that "temperatures in the latter half of the 20th century were unprecedented," and the IPCC's and Environment Canada's confident assertions that the 1990s was "likely the warmest decade" and 1998 the "warmest year" of the millennium, are wholly unsubstantiated.
Among the many mistakes in Mann's paper, some appear blatant, some simply careless apparently due to clerical errors (for example, allocating measurements to the wrong years, "filling" tables with identical numbers for different proxies in different years, etc.). In many cases, obsolete source data was used that have since been revised by the originating researchers. As an example of their numerous "truncation errors," Mann's Central England Temperature series stops without explanation at 1730, even though data are available back to 1659, thus hiding a major 17th century cold period. Similarly, Central Europe data are truncated at 1550, rather than 25 years earlier, for which the data are available, the effect being to remove the warmest data in the series. Of course, no one with an understanding of climate history really believes there was a dramatic temperature spike in the middle of the Little Ice Age. Yet Mann's data and methodology actually supports such a notion, completely contradicting his contention that there was merely a gradually cooling between 1000 AD and 1900.
Correcting and updating the proxy database used by Mann and his co-authors and then repeating Mann's methodology, McIntyre and McKitrick showed that the MBH98 study in fact reveals that the late 20th century Northern Hemisphere temperature trend is unexceptional compared to the preceding centuries. In doing so, they demonstrate the sort of in-depth analysis the IPCC should have conducted on its own. Instead, its so called "rigorous review process" failed miserably, giving highly flawed work central prominence in the 2001 IPCC Report. As a consequence, governments worldwide are now making some of their most expensive policy decisions ever based on uncritical acceptance of an IPCC Report that we now know to be decidedly unsound in itself.
Dr. Tim Patterson is a professor in the Department of Earth Sciences at Carleton University.