The New View of Natural Climate Variation

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"The New View of Natural Climate Variation"

Journal article

By: David E. Wojick

Date: January 2003

Source: Wojick, David L. "The New View of Natural Climate Variation." American Petroleum Institute, January 2003.

About the Author: David E. Wojick received his Bachelor of Science degree in civil engineering from Carnegie-Mellon University in 1964 and his Doctor of Philosophy degree from the University of Pittsburgh in 1974, where he studied mathematical logic and conceptual analysis. His doctoral thesis involved the analysis of scientific and technological breakthroughs. Wojick was a water resources engineer for the Civil Works program of the Army Corps of Engineers from 1965 to 1970; a faculty member of Carnegie-Mellon University from 1970 to 1976; and the head of the independent consulting and research group Adams & Wojick Associates from 1981 to 1999. He is also the founder and president of; a science journalist who covers climate change topics for Electricity Daily; and a consultant to the energy industry. His professional expertise includes issue analysis, strategic planning, and technology forecasting, especially with regard to climate science.


The article "The New View of Natural Climate Variation: Fundamental Climate Science Issues Raised in Six Major National Academy of Science Studies" is the result of a study conducted by environmental consultant Dr. Wojick. In the article, he focused on the important uncertainties in the area of worldwide climate changes. The study was prompted by an announcement of the President George W. Bush administration that a critical review of the U.S. Global Change Research Program would be soon performed. Central to the scientific review performed by Wojick was the resolution of various major uncertainties with respect to world climate variations. The article was the basis for Wojick's presentation to the Climate Change Task Force, which met on January 14, 2003.


Six different National Academy of Science [NAS] reports since 1998 have identified very fundamental questions that have to be faced when making a credible assessment of climate change—and our current ability to understand and project possible change in the future. In many instances new scientific research is beginning to address some of these key issues, but just beginning.

When viewed in their entirety, these NAS reports go to the very core of the question of "uncertainty" in climate modeling. Traditionally, "uncertainty" has been interpreted as an "error bar"—for a given increase in Greenhouse Gas (GHG) emissions, what is the range of likely and/or potential increases in global temperature?

The issues in the NAS reports and recent research are far more fundamental and clash with an underlying premise of much climate modeling over the past decade—that climate over the past century and a half has been effectively constant and any changes are primarily because of man's activity. As stated by the National Academy of Sciences: "The evidence of natural variations in the climate system—which was once assumed to be relatively stable—clearly reveals that climate has changed, is changing, and will continue to do so with or without anthropogenic influences." (Dec-Cen Variability, Summary.)

If climate has been as volatile on decade to century or longer scales as is now become apparent, due to multiple mechanisms, then the following deep questions arise:

  • Do we have an accurate understanding of past climate changes?
  • Do we know what has caused past changes in climate?
  • Do we know why climate is changing today?
  • Do we know how to model these mechanisms?
  • Can we separate the impact of these new factors from the potential influence of greenhouse gas emissions or other potential anthropogenic impacts?

What is so important is that this understanding—of what we do not understand—is a recent development.

The difference our newfound lack of understanding makes is also simple. In a naturally changing climate rather than a stable climate, it is far more difficult to tell if and how human activities have had a discernible influence on climate, or how human activities may influence the future. Since we do not yet know why climate changes, we do not yet know why it has changed in the last century, or even how it has changed. We also cannot yet say how it is likely to change in the future.

The conclusion is obvious. We must now direct our climate change research effort to confront our newly found lack of understanding. A decade of research has taught us what we don't know.

It has taught us important questions. Now we must seek the answers. This report has a single goal. That goal is to catalog key uncertainties in a naturally varying climate system—uncertainties that range from observation to explanation to modeling—that have been clearly documented in at least six major studies by the U.S. National Academy of Sciences. These studies were:

  • Abrupt Climate Change: Inevitable Surprises (2001);
  • Climate Change Science: An Analysis of Some Key Questions (2001);
  • Decade-to-Century-Scale Climate Variability and Change: A Science Strategy (1998);
  • Global Environmental Change: Research Pathways for the Next Decade (1999);
  • Issues in the Integration of Research and Operational Satellite Systems for Climate Research: Part I. Science and Design (2000);
  • Research: Part I. Science and Design (2000); and
  • The Atmospheric Sciences: Entering the Twenty-First Century (1998).

The descriptions of these key uncertainties have been scattered within these reports, numbering thousands of pages, and thus are not clearly or widely recognized.

So, in keeping with the rest of this report, we here present a set of quotes from these major NAS studies that clearly state what we have just said—we do not know the extent of climate change in the past, we do not know why climate changes, and we must focus our research on this issue. Only then can we integrate the potential role of past increases in GHG emissions into recent climate history, and only then can we begin to assess the outlook for future climate.

"Climate research on decade to century ("dec-cen") timescales is relatively new. Only recently have we obtained sufficient high-resolution paleoclimate records, and acquired faster computers and improved models allowing long-term simulations, to examine past change on these timescales. This research has led to genuinely novel insights, most notably that the past assumption of a relatively stable climate state on dec-cen timescales since the last glaciation is no longer a viable tenet. The paleorecords reveal considerable variability occurring over all timescales, while modeling and theoretical studies indicate modes of internal and coupled variability driving variations over dec-cen timescales as well." (Pathways, p. 129.)

"Thus, dec-cen climate research is only at the beginning of its learning curve, with dramatic findings appearing at an impressive rate. In this area even the most fundamental scientific issues are evolving rapidly. Adaptability to new directions and opportunities is therefore imperative to advance understanding of climate variability and change on these timescales." (Pathways, p. 129.)

"To date, we do not have a comprehensive inventory of global patterns, nor do we understand their mechanisms, couplings, longevity, or full implications for climate predictions." (Pathways, p. 140.)

"The new paradigm of an abruptly changing climatic system has been well established by research over the last decade, but this new thinking is little known and scarcely appreciated in the wider community of natural and social scientists and policymakers." (Abrupt Climate Change, p. 1.)

"The climate change and variability that we experience will be a commingling of the ever changing natural climate state with any anthropogenic change. While we are ultimately interested in understanding and predicting how climate will change, regardless of the cause, an ability to differentiate anthropogenic change from natural variability is fundamental to help guide policy decisions, treaty negotiations, and adaptation versus mitigation strategies. Without a clear understanding of how climate has changed naturally in the past, and the mechanisms involved, our ability to interpret any future change will be significantly confounded and our ability to predict future change severely curtailed." (Dec-Cen Variability, Preface.)

"Large gaps in our knowledge of interannual and decade-to-century natural variability hinder our ability to provide credible predictive skill or to distinguish the role of human activities from natural variability. Narrowing these uncertainties and applying our understanding define the mission of climate and climate change research and education for the twenty-first century." (Atmospheric Sciences, p. 278.)

"For example, is the accelerated warming the result of natural variability caused by an unusually persistent coincidence of the NAO [North Atlantic Oscillation] and PNA [Pacific-North American teleconnection], or the result of the modification of natural modes (patterns) by anthropogenic changes in radiative forcing that alter the phasing, or some combination of both of these? Likewise, there appears to have been a distinct change in the character (frequency and severity) of El Niño and La Niña events during this period of accelerated warming. Is this a consequence of the influence of anthropogenic change on the dominant natural modes of climate variability, or is it a natural, low-frequency (dec-cen) modulation of a high-frequency (interannual) mode?" (Dec-Cen Variability, Summary.)

"The characteristic scales of climate variability demand long time series in order to determine the critical processes as well as to separate natural variability from anthropogenic influences. Unlike weather forecasting, the interval between stimulus and response can be years to centuries. With a high level of background variability, subtle changes in Earth's climate system can be difficult to detect." (Integration of Research and Satellites, p. 8.)

"A satisfactory demonstration of secular trends in the Earth's climate system … requires analysis at the forefront of science and statistical analysis. Model predictions have been available for decades, but a clear demonstration of their validity, a demonstration that will convince a reasoned critic on cross examination, is not yet available. This is not in itself either a statement of failure or a significant surprise. Rather, it is a measure of the intellectual depth of the problem and the need for carefully orchestrated, long term observations." (Pathways, p. 522.)

"Climate variability and change on decade to century timescales involves all of the elements of the U.S. Global Change Research Program: natural and anthropogenic variability and change; past, present, and future observational networks and databases; modeling requirements; and physical, chemical, biological, and social sciences, with considerable attention to the human dimensions of climate change." (Pathways, pp. 129-130.)

"Recommendation 1: Research priorities and resource allocations must be reassessed, with the objective of tying available resources directly to the major unanswered Scientific Questions identified in this report. The USGCRP's research strategy should be centered on sharply defined and effectively executed programs and should recognize the essential need for focused observations, both space-based and in situ, to test scientific hypotheses and document change." (Pathways, p. 521.)

"Recommendation 2: Following on Recommendation 1, the national strategy of the USGCRP for Earth observations must be restructured and must be driven by the key unanswered Scientific Questions." (Pathways, p. 523.)

Natural climate variability is a key element in the "major unanswered Scientific Questions" referred to above and is the topic of this report. Taken together, they present a new view of climate change, a view dominated by natural variation, in ways we do not yet understand. The implications of this new view of natural variability and the NAS studies is clear and stated succinctly in Climate Change Science: An Analysis of Some Key Questions:

"Predictions of global climate change will require major advances in understanding and modeling …" (Climate Change Science, p 23.)


Wojick based his paper on six different National Academy of Science (NAS) reports that were published between 1998 and 2003. Within these NAS reports, fundamental questions were identified whose solutions were seen by Wojick as key information needed before valid scientific assessments could be made of global climate changes in the past, present, and future. Within his article, Wojick systematically described the greatest climate science uncertainties faced by humanity. The following questions are seen by Wojick as the major uncertainties:

  • What is the state of the Earth, present and past?
  • How much and when has the Earth warmed?
  • Why does climate change?
  • How does climate work?
  • Can we predict climate?
  • How uncertain are we?

Wojick went on to state in his report some of the principle variations that naturally causes changes in worldwide climate. These principle variations include:

  • Aerosol forcing mechanisms (methods that increase the types and amounts of microscopic airborne particles)
  • Biospheric (which is the layer of air, soil, and water that is capable of supporting life)
  • Cryogenic (materials at very low temperatures such as ice sheets, along with conditions involving land-ice layers)
  • Direct and indirect solar energy (such as the effects of solar winds on the Earth's magnetic field)
  • Hydrologic cycle (the various movements of water above and below the Earth's surface, including its storage, runoff, and changes within permafrost)
  • Internal oscillations of the Earth such as PDO (Pacific Decadal Oscillation), NAO (North Atlantic Oscillation), AO (Artic Oscillation), ENSO (El Niño/Southern Oscillation), and Milankovitch Cycles (variations in the Earth's orbit)
  • Ocean (such as water circulation and, especially, deepwater formations)
  • Surface versus satellite temperature (such as vertical distribution of temperature in the atmosphere and how its behavior changes over time).

Based on these NAS reports and recent research performed in the field of climate science, Wojick disagreed with the currently accepted belief that the natural climate of the Earth is basically constant and the climate changes seen over the past hundred years are due only to human activities (or what is scientifically called "anthropogenic influences"). In fact, Wojick claimed that the (perceived) warming of the Earth by human-produced greenhouse gas emissions has had no more effect on world climate changes than the natural variations of the Earth. Further, he stated that although scientists have increased their overall scientific knowledge of climate change on Earth, the increase in that knowledge has been offset by a decrease in the amount of certainty with respect to mankind's contribution to such changes.

From the Decade-to-Century-ScaleClimate Variability and Change: A Science Strategy report, Wojick quotes: "The evidence of natural variations in the climate system—which was once assumed to be relatively stable—clearly reveals that climate has changed, is changing, and will continue to do so with or without anthropogenic [human] influences."

If what Wojick reported is correct, and further scientific studies verify his statements, it is believed by many climatologists that it will be much more difficult to differentiate between natural climate variations and artificial climate variations caused by human activities. Wojick concluded in his report: "we do not know the extent of climate change in the past, we do not know why climate changes, and we must focus our research on this issue. Only then can we integrate the potential role of past increases in GHG emissions into recent climate history, and only then can we begin to assess the outlook for future climate."


Web sites 〈〉 (accessed November 26, 2005).

Cooler Heads Coalition, "Climate Variation is the Norm, Not the Exception." 〈〉 (accessed November 26, 2005).

The Dartmouth Review. "TDR Interview: Dr. David Wojick." 〈〉 (accessed November 26, 2005).

President's Council on Sustainable Development. "Climate Change Task Force." 〈〉 (accessed November 26, 2005).

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The New View of Natural Climate Variation

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