July 12, 2018
Dear Friends and Family,
This is Segment 6 of the Climate Change Series and focuses on the Hockey Stick graph produced by Dr. Michael Mann and two of his colleagues. All of the excerpts are from The Hockey Stick and Climate Wars by Dr. Michael E. Mann. The following is Michael Mann’s graph of the average annual temperature of the Northern Hemisphere, as presented in The New Scientist (16 May 2007).
Dear Friends and Family,
This is Segment 6 of the Climate Change Series and focuses on the Hockey Stick graph produced by Dr. Michael Mann and two of his colleagues. All of the excerpts are from The Hockey Stick and Climate Wars by Dr. Michael E. Mann. The following is Michael Mann’s graph of the average annual temperature of the Northern Hemisphere, as presented in The New Scientist (16 May 2007).
You will note that for the first 900 years the line is virtually flat indicating the temperature variation from average was extremely small (varying from about 0.05 to -0.4 degrees C.) At year 1880 the temperature line increases about 0.2 degrees C for about 60 years. At that point the temperature line goes up in an almost a straight line to about 0.7 degrees C. Hence it looks like a hockey stick on its side with a very straight handle which then curves to flat part of the stick at almost 90 degrees.
This graph and how it was developed will be the subject of the next three segments as it is the critical piece of data supporting the Climate Change Advocates position, this quote from The Hockey Stick Illusion illustrates:
“In the years that followed more and more interest was focused on the Hockey Stick. In particular, it was one of the key arguments used to support the need for the Kyoto treaty. Citations of Mann’s work flooded-in and its influence and importance grew without restraint, until it came to symbolize the very idea of manmade global warming. As one BBC reporter put it, ‘it is hard to overestimate how influential this study has been’. Every home in Canada was sent a leaflet quoting the Hockey Stick’s conclusions and warning of the dangers of climate change. School books told children that the Hockey Stick meant that the world had to change. Politicians told voters that only they could save people from the threat it demonstrated.”
Dr. Mann first published his Hockey Stick findings in 1998, but didn’t publish his book, which is the source of the excerpts, until 2013. In that 15-year period there was extreme controversy over the Hockey Stick which Dr. Mann terms as the Climate Wars. The excerpts which follow provides a technical explanation of Mann’s work. The PDF attachment at the bottom of the excerpts will provide a better sense of the controversy as it includes Dr. Mann’s defense of his scientific conclusions.
The following are the answers from The Hockey Stick and Climate Wars book relative to the list of questions we utilized the cover letters of segment 2 through 5.
· Evidence derived from General Circulation Models (GSMs)
The next segment will be the first of two counterpoint segments to Dr. Mann’s Hockey Stick book. The segments excerpts will be exclusively from The Hockey Stick Illusion written by A. W. Montford.
Happy Learning,
Harley
This graph and how it was developed will be the subject of the next three segments as it is the critical piece of data supporting the Climate Change Advocates position, this quote from The Hockey Stick Illusion illustrates:
“In the years that followed more and more interest was focused on the Hockey Stick. In particular, it was one of the key arguments used to support the need for the Kyoto treaty. Citations of Mann’s work flooded-in and its influence and importance grew without restraint, until it came to symbolize the very idea of manmade global warming. As one BBC reporter put it, ‘it is hard to overestimate how influential this study has been’. Every home in Canada was sent a leaflet quoting the Hockey Stick’s conclusions and warning of the dangers of climate change. School books told children that the Hockey Stick meant that the world had to change. Politicians told voters that only they could save people from the threat it demonstrated.”
Dr. Mann first published his Hockey Stick findings in 1998, but didn’t publish his book, which is the source of the excerpts, until 2013. In that 15-year period there was extreme controversy over the Hockey Stick which Dr. Mann terms as the Climate Wars. The excerpts which follow provides a technical explanation of Mann’s work. The PDF attachment at the bottom of the excerpts will provide a better sense of the controversy as it includes Dr. Mann’s defense of his scientific conclusions.
The following are the answers from The Hockey Stick and Climate Wars book relative to the list of questions we utilized the cover letters of segment 2 through 5.
- Is there a 20th century temperature rising trend acknowledged? Yes, definitely.
- Is that trend attributed to fossil fuel emissions? Yes
- What is the evidence cited to support point 2 above?
· Evidence derived from General Circulation Models (GSMs)
- Is the trend attributed to natural causes? No
- Are there severe consequences predicted? Yes
- Is there any additional scientific information presented concerning the debate? No
The next segment will be the first of two counterpoint segments to Dr. Mann’s Hockey Stick book. The segments excerpts will be exclusively from The Hockey Stick Illusion written by A. W. Montford.
Happy Learning,
Harley
CLIMATE CHANGE – SEGMENT 6
THE HOCKEY STICK, CONCEPT - EXCERPTS
NOTE: All excerpts in this segment are from The Hockey Stick (2012) by Michael E. Mann
INTRODUCTION: A central figure in the climate change controversy has been the "hockey stick" a simple, easy-to-understand graph, my colleagues, and I constructed to depict changes in Earth's temperature back to A.D. 1000. The graph was featured in the high-profile "Summary for Policy Makers' of the 2001 report of the Intergovernmental Panel on Climate Change (IPCC), and it quickly became an icon in the debate over human-caused climate change.
Proxy records, such as tree rings, ice cores, corals, and lake sediments can potentially tell us about climate conditions such as temperature, rainfall, or wind patterns for a single year or season. By using an array of such records, we can establish a year-by-year chronology of the climate changes of past centuries. We published our original findings, in 1998. The picture that emerged was a wiggly curve dominating past temperature changes over the entire Northern Hemisphere (the hemisphere with the most data) and indicating a sharp rise in temperature over the past century. The graph we drew looked fuzzy because for each point on the curve it included the margin of error, reflecting the simple fact that ice cores, coral, tree rings, and other proxies are useful but rather imperfect thermometers.
Despite the uncertainties, my coauthors and I were able to draw certain important conclusions. We deduced that there had been a decline in temperature from the period running from the eleventh century through the fourteenth – a period sometime referred to as the medieval warm period – into the colder Little Ice Age of the fifteenth to nineteenth centuries. Think of this as the shaft of a hockey stick laid on it back. This long-term gradual decline was followed by an abrupt upturn in temperatures over the past century. Thus, was born the hockey stick. It didn't take long for the hockey stick to become a central icon for the climate change debate.
CLIMATE CHANGE IN FIVE EASY STEPS
(1). We know for one thing that human activity – primarily the burning of fossil fuels – has increased CO2 concentration in the atmosphere. We had an instrument record of CO2 going back nearly half a century. These records indicate a steady two-century rise in CO2 co-incident with the Industrial Revolution, culminating in modern levels that appear unprecedented in hundreds of thousands of years, at least, long before modern humans were on the scene. At current rates of fossil fuel burning CO2 concentrations, it was estimated, would reach twice preindustrial levels within about four decades.
(2). Scientists also knew that this increase in atmospheric CO2 must have a warming effect on Earth's surface. The effect is known as the "greenhouse effect," and the gases responsible for it are thus termed "greenhouse gases."
(3). Thermometer measurements told us that by the mid-1990s Earth had already warmed a little more than a degree F. since the dawn of industrialization. The globe was in fact warming.
(4). By the mide-1990s, it was possible to investigate the causal mechanisms behind changes in Earth's climate using relatively sophisticated mathematical models of Earth's climate.
(5). Finally, perhaps most significant of all, only when human factors were included could the models reproduce the observed warming – both its overall magnitude and, equally important, its geographical pattern over Earth's surface and its vertical pattern in the atmosphere. The pattern of warming predicted by the models from the combination of these two human effects on the climate proved a unique "fingerprint" of what the human influence of climate should look like if the models were correct – and the fingerprint matched. The fingerprint predicted for natural factors alone – for example, from fluctuations in solar output – on the other hand, failed to match the observations. Scientists during the mid-1990s established this fingerprint of human influence that provided the "smoking gun," the fifth and final link in the chain of reasoning that allowed the IPCC to declare in 1996 that there was indeed at least a "discernible" human influence on the climate. What scientists were still debating with each other at scientific meetings and in the professional journals was the precise balance of human versus natural causes in the changes observed thus far, and just what further changes might loom in our future.
Answers to these more specific questions were far less clear. Climate scientists could surmise that if human civilization continued to follow its current upward trajectory of fossil fuel burning, we would likely see a near doubling of preindustrial atmospheric CO2 levels by the mid-twenty-first century. Furthermore, we could estimate that such an increase would lead to an additional warming of anywhere between 3 to 8 degrees F. The large spread in estimated temperature increase arose primarily from uncertainty about the effect of so-called feedbacks, responses of the system that can either further amplify or diminish the warming. Certain feedbacks are almost certainly positive, amplifying the given effect; for example, a warmer atmosphere holds more water vapor, and water vapor is itself a greenhouse gas, further warming the surface. The melting of ice as Earth warms exposes more of the ground and ocean surface. These surfaces absorb sunlight more effectively that does ice, which further amplifies the warming. But other factors, such as how clouds change under warmer conditions and to what effect, were highly uncertain, and remain so still.
MEDIEVAL WARM PERIOD: As more widespread climate proxy records were developed through the early 1990s and researchers were able to begin to piece together a picture of the larger-scale patterns of climate during medieval times, a more nuanced view of this period emerged. While various regions of the globe – including parts of Europe, China, western North America and Australia – appear to have been relatively warm by modern standards during some part of the medieval era, the warmth did not appear synchronous among the regions. Other regions, including the southeastern United States and the Mediterranean, showed no evidence of warmth that rival modern levels. Moreover, many of the more profound changes in regional climate that paleoclimate researchers were discovering were tied to shifts in atmospheric circulation and rainfall patterns, rather than to changes in temperature. For these reasons, paleoclimate researchers have increasingly favored the use of the term “medieval climate anomaly” (MCA) over the potentially misleading “medieval warm period” moniker.
THE THIRD ASSESSMENT REPORT: In order to understand the rise to prominence of the hockey stick, it is necessary to delve into the history behind the IPCC Third Assessment Report published in 2001. It was in that publication that our work truly entered onto the world stage. I was still relatively fresh out of graduate school, and I was surprised when I learned in late 1998 that I had been selected as a lead author for the new report. My task as lead author was to work with the numerous contributing authors in assessing the state of knowledge regarding evidence from the paleoclimate record. To be credible as a true assessment of prevailing scientific understanding, IPCC reports must accurately reflect the diverse views within the scientific community on any particular issue. Since the IPCC report is an assessment report, it is necessary that the IPCC evaluate the collective work of the scientific community in such a way that it is clear to readers on what points scientists agree, and where there is still active debate. Any key conclusions arising from the chapter could not rely on one study or one group’s findings. They had to reflect a consensus of recent studies, if indeed that existed. The hockey stick was shown in a plot by itself for two important reasons: (1) it was the only reconstruction done at the level of individual years rather than decadal or longer-term averages, and (2) it came with error bars, which the other reconstructions didn’t. After much discussion among all the lead authors, a consensus was reached on a tentative conclusion. The word likely, the group decided, should be attached to the conclusion that recent warming for the Northern Hemisphere. In the parlance of the IPCC, this careful phrasing indicated confidence of about 67%, that is, a two-out-of-three chance that the conclusion was correct.
IMPLICATIONS: Suppose we were to continue with business as usual, shunning efforts to curtail carbon emissions. The impacts on our civilization and environment could be profound. By doing so, we might well be committing ourselves to the melting of the major ice sheets, resulting in a sea level rise as much as six feet by the end of the century and, eventually, twenty feet or more, thus ensuring extensive loss of coastal settlements around the world, including the East and Gulf Coasts of the United States. Destruction from potentially more powerful hurricanes fueled by warmer oceans. Increasingly widespread and severe droughts would likely take hold over the major continents, including North America, as precipitation became increasingly intermittent and moisture evaporated more readily from warmer soils. Many regions would likely also see increased flooding from more intense rainfall events. Among the potential impacts would be greater social conflict resulting from movements of large numbers of environmental refugees and increased competition for available resources within and among nations, more widespread famine due to declining agricultural production in developing tropical nations already struggling with hunger and malnutrition, and threats to human health and even mortality from potential increases in the spread of infectious disease and stress-related deaths from more frequent and extreme heat waves. Key ecosystems lost, including coral reefs and the summer Arctic sea ice environmentally critical to the survival of polar bears.
EPILOGUE: As of late 2011, carbon dioxide concentrations are at roughly 392 ppm. A year and a half earlier, when I began writing this book, they were at 338 ppm. When we reach concentrations of 450 ppm (about 2030, extrapolating from current trends), we will likely have locked in at least 3.5 degrees F warming of the climate relative to preindustrial levels, a level experts generally agree constitutes dangerous human interference with the climate system, far beyond what we have thus far witnessed.
2012 saw the lowest domestic U.S. carbon emissions in twenty years. This has generally been attributed to a shift away from a more carbon intensive fossil fuel – coal—to a less intensive one – natural gas. That can only slow down the rate of increased emissions; it doesn’t move us towards minimal carbon emission, which is where we need to go. That would ultimately require meeting our energy needs almost entirely from non-fossil fuel emission from any residual fossil fuel burning – something that studies indicate is doable. But if nothing else, the sharp drop in U.S. emissions over the past years (15% relative to previous peak) is evidence that market forces can modify our energy choices quickly and dramatically. We just need to get the incentive and regulatory structure right so that, coupled with popular demand, we can move rapidly in the direction of a predominantly non-carbon based energy economy.
The unabbreviated version of the above can be found in the pdf document below.
THE HOCKEY STICK, CONCEPT - EXCERPTS
NOTE: All excerpts in this segment are from The Hockey Stick (2012) by Michael E. Mann
INTRODUCTION: A central figure in the climate change controversy has been the "hockey stick" a simple, easy-to-understand graph, my colleagues, and I constructed to depict changes in Earth's temperature back to A.D. 1000. The graph was featured in the high-profile "Summary for Policy Makers' of the 2001 report of the Intergovernmental Panel on Climate Change (IPCC), and it quickly became an icon in the debate over human-caused climate change.
Proxy records, such as tree rings, ice cores, corals, and lake sediments can potentially tell us about climate conditions such as temperature, rainfall, or wind patterns for a single year or season. By using an array of such records, we can establish a year-by-year chronology of the climate changes of past centuries. We published our original findings, in 1998. The picture that emerged was a wiggly curve dominating past temperature changes over the entire Northern Hemisphere (the hemisphere with the most data) and indicating a sharp rise in temperature over the past century. The graph we drew looked fuzzy because for each point on the curve it included the margin of error, reflecting the simple fact that ice cores, coral, tree rings, and other proxies are useful but rather imperfect thermometers.
Despite the uncertainties, my coauthors and I were able to draw certain important conclusions. We deduced that there had been a decline in temperature from the period running from the eleventh century through the fourteenth – a period sometime referred to as the medieval warm period – into the colder Little Ice Age of the fifteenth to nineteenth centuries. Think of this as the shaft of a hockey stick laid on it back. This long-term gradual decline was followed by an abrupt upturn in temperatures over the past century. Thus, was born the hockey stick. It didn't take long for the hockey stick to become a central icon for the climate change debate.
CLIMATE CHANGE IN FIVE EASY STEPS
(1). We know for one thing that human activity – primarily the burning of fossil fuels – has increased CO2 concentration in the atmosphere. We had an instrument record of CO2 going back nearly half a century. These records indicate a steady two-century rise in CO2 co-incident with the Industrial Revolution, culminating in modern levels that appear unprecedented in hundreds of thousands of years, at least, long before modern humans were on the scene. At current rates of fossil fuel burning CO2 concentrations, it was estimated, would reach twice preindustrial levels within about four decades.
(2). Scientists also knew that this increase in atmospheric CO2 must have a warming effect on Earth's surface. The effect is known as the "greenhouse effect," and the gases responsible for it are thus termed "greenhouse gases."
(3). Thermometer measurements told us that by the mid-1990s Earth had already warmed a little more than a degree F. since the dawn of industrialization. The globe was in fact warming.
(4). By the mide-1990s, it was possible to investigate the causal mechanisms behind changes in Earth's climate using relatively sophisticated mathematical models of Earth's climate.
(5). Finally, perhaps most significant of all, only when human factors were included could the models reproduce the observed warming – both its overall magnitude and, equally important, its geographical pattern over Earth's surface and its vertical pattern in the atmosphere. The pattern of warming predicted by the models from the combination of these two human effects on the climate proved a unique "fingerprint" of what the human influence of climate should look like if the models were correct – and the fingerprint matched. The fingerprint predicted for natural factors alone – for example, from fluctuations in solar output – on the other hand, failed to match the observations. Scientists during the mid-1990s established this fingerprint of human influence that provided the "smoking gun," the fifth and final link in the chain of reasoning that allowed the IPCC to declare in 1996 that there was indeed at least a "discernible" human influence on the climate. What scientists were still debating with each other at scientific meetings and in the professional journals was the precise balance of human versus natural causes in the changes observed thus far, and just what further changes might loom in our future.
Answers to these more specific questions were far less clear. Climate scientists could surmise that if human civilization continued to follow its current upward trajectory of fossil fuel burning, we would likely see a near doubling of preindustrial atmospheric CO2 levels by the mid-twenty-first century. Furthermore, we could estimate that such an increase would lead to an additional warming of anywhere between 3 to 8 degrees F. The large spread in estimated temperature increase arose primarily from uncertainty about the effect of so-called feedbacks, responses of the system that can either further amplify or diminish the warming. Certain feedbacks are almost certainly positive, amplifying the given effect; for example, a warmer atmosphere holds more water vapor, and water vapor is itself a greenhouse gas, further warming the surface. The melting of ice as Earth warms exposes more of the ground and ocean surface. These surfaces absorb sunlight more effectively that does ice, which further amplifies the warming. But other factors, such as how clouds change under warmer conditions and to what effect, were highly uncertain, and remain so still.
MEDIEVAL WARM PERIOD: As more widespread climate proxy records were developed through the early 1990s and researchers were able to begin to piece together a picture of the larger-scale patterns of climate during medieval times, a more nuanced view of this period emerged. While various regions of the globe – including parts of Europe, China, western North America and Australia – appear to have been relatively warm by modern standards during some part of the medieval era, the warmth did not appear synchronous among the regions. Other regions, including the southeastern United States and the Mediterranean, showed no evidence of warmth that rival modern levels. Moreover, many of the more profound changes in regional climate that paleoclimate researchers were discovering were tied to shifts in atmospheric circulation and rainfall patterns, rather than to changes in temperature. For these reasons, paleoclimate researchers have increasingly favored the use of the term “medieval climate anomaly” (MCA) over the potentially misleading “medieval warm period” moniker.
THE THIRD ASSESSMENT REPORT: In order to understand the rise to prominence of the hockey stick, it is necessary to delve into the history behind the IPCC Third Assessment Report published in 2001. It was in that publication that our work truly entered onto the world stage. I was still relatively fresh out of graduate school, and I was surprised when I learned in late 1998 that I had been selected as a lead author for the new report. My task as lead author was to work with the numerous contributing authors in assessing the state of knowledge regarding evidence from the paleoclimate record. To be credible as a true assessment of prevailing scientific understanding, IPCC reports must accurately reflect the diverse views within the scientific community on any particular issue. Since the IPCC report is an assessment report, it is necessary that the IPCC evaluate the collective work of the scientific community in such a way that it is clear to readers on what points scientists agree, and where there is still active debate. Any key conclusions arising from the chapter could not rely on one study or one group’s findings. They had to reflect a consensus of recent studies, if indeed that existed. The hockey stick was shown in a plot by itself for two important reasons: (1) it was the only reconstruction done at the level of individual years rather than decadal or longer-term averages, and (2) it came with error bars, which the other reconstructions didn’t. After much discussion among all the lead authors, a consensus was reached on a tentative conclusion. The word likely, the group decided, should be attached to the conclusion that recent warming for the Northern Hemisphere. In the parlance of the IPCC, this careful phrasing indicated confidence of about 67%, that is, a two-out-of-three chance that the conclusion was correct.
IMPLICATIONS: Suppose we were to continue with business as usual, shunning efforts to curtail carbon emissions. The impacts on our civilization and environment could be profound. By doing so, we might well be committing ourselves to the melting of the major ice sheets, resulting in a sea level rise as much as six feet by the end of the century and, eventually, twenty feet or more, thus ensuring extensive loss of coastal settlements around the world, including the East and Gulf Coasts of the United States. Destruction from potentially more powerful hurricanes fueled by warmer oceans. Increasingly widespread and severe droughts would likely take hold over the major continents, including North America, as precipitation became increasingly intermittent and moisture evaporated more readily from warmer soils. Many regions would likely also see increased flooding from more intense rainfall events. Among the potential impacts would be greater social conflict resulting from movements of large numbers of environmental refugees and increased competition for available resources within and among nations, more widespread famine due to declining agricultural production in developing tropical nations already struggling with hunger and malnutrition, and threats to human health and even mortality from potential increases in the spread of infectious disease and stress-related deaths from more frequent and extreme heat waves. Key ecosystems lost, including coral reefs and the summer Arctic sea ice environmentally critical to the survival of polar bears.
EPILOGUE: As of late 2011, carbon dioxide concentrations are at roughly 392 ppm. A year and a half earlier, when I began writing this book, they were at 338 ppm. When we reach concentrations of 450 ppm (about 2030, extrapolating from current trends), we will likely have locked in at least 3.5 degrees F warming of the climate relative to preindustrial levels, a level experts generally agree constitutes dangerous human interference with the climate system, far beyond what we have thus far witnessed.
2012 saw the lowest domestic U.S. carbon emissions in twenty years. This has generally been attributed to a shift away from a more carbon intensive fossil fuel – coal—to a less intensive one – natural gas. That can only slow down the rate of increased emissions; it doesn’t move us towards minimal carbon emission, which is where we need to go. That would ultimately require meeting our energy needs almost entirely from non-fossil fuel emission from any residual fossil fuel burning – something that studies indicate is doable. But if nothing else, the sharp drop in U.S. emissions over the past years (15% relative to previous peak) is evidence that market forces can modify our energy choices quickly and dramatically. We just need to get the incentive and regulatory structure right so that, coupled with popular demand, we can move rapidly in the direction of a predominantly non-carbon based energy economy.
The unabbreviated version of the above can be found in the pdf document below.
| 06_cc_long_hockey_stick_--_segment_6.pdf |