Earth’s Deep Past
Lessons for Our Climate Future
Committee on the
Importance of Deep-Time Geologic Records for
Understanding Climate Change Impacts
Board on Earth Sciences and Resources
Division on Earth and Life Studies
NATIONAL RESEARCH COUNCIL
OF THE NATIONAL ACADEMIES
THE NATIONAL ACADEMIES PRESS
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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.
This study was supported by the National Science Foundation under Grant No. EAR-0625247, the U.S. Geological Survey under Award No. 06HQGR0197, and the Chevron Corporation. The opinions, findings, and conclusions or recommendations contained in this document are those of the authors and do not necessarily reflect the views of the National Science Foundation, the U.S. Geological Survey, or the Chevron Corporation.
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COMMITTEE ON THE IMPORTANCE OF DEEP-TIME GEOLOGIC RECORDS FOR UNDERSTANDING CLIMATE CHANGE IMPACTS
ISABEL P. MONTAÑEZ, Chair (2010-2011), University of California, Davis
RICHARD D. NORRIS, Chair (2007-2009), Scripps Institution of Oceanography, San Diego, California
THOMAS ALGEO, University of Cincinnati, Ohio
MARK A. CHANDLER, Columbia University, New York
KIRK R. JOHNSON, Denver Museum of Nature and Science, Colorado
MARTIN J. KENNEDY, University of Adelaide, South Australia
DENNIS V. KENT, Rutgers, The State University of New Jersey, Piscataway
JEFFREY T. KIEHL, National Center for Atmospheric Research, Boulder, Colorado
LEE R. KUMP, The Pennsylvania State University, University Park
A. CHRISTINA RAVELO, University of California, Santa Cruz
KARL K. TUREKIAN, Yale University, New Haven, Connecticut
Liaison from the Board on Earth Sciences and Resources
KATHERINE H. FREEMAN, The Pennsylvania State University, University Park
National Research Council Staff
DAVID A. FEARY, Study Director
NICHOLAS D. ROGERS, Research Associate
JENNIFER T. ESTEP, Financial and Administrative Associate
COURTNEY R. GIBBS, Program Associate
ERIC J. EDKIN, Senior Program Assistant
BOARD ON EARTH SCIENCES AND RESOURCES
CORALE L. BRIERLEY, Chair, Brierley Consultancy LLC, Denver, Colorado
KEITH C. CLARKE, University of California, Santa Barbara
DAVID J. COWEN, University of South Carolina, Columbia
WILLIAM E. DIETRICH, University of California, Berkeley
ROGER M. DOWNS, The Pennsylvania State University, University Park
JEFF DOZIER, University of California, Santa Barbara
WILLIAM. L. GRAF, University of South Carolina, Columbia
RUSSELL J. HEMLEY, Carnegie Institution of Washington, Washington, D.C.
MURRAY W. HITZMAN, Colorado School of Mines, Golden
EDWARD KAVAZANJIAN, Jr., Arizona State University, Tempe
ROBERT B. McMASTER, University of Minnesota, Minneapolis
M. MEGHAN MILLER, UNAVCO, Inc., Boulder, Colorado
ISABEL P. MONTAÑEZ, University of California, Davis
CLAUDIA INÉS MORA, Los Alamos National Laboratory, New Mexico
BRIJ M. MOUDGIL, University of Florida, Gainesville
CLAYTON R. NICHOLS, Idaho National Engineering and Environmental Laboratory (retired), Ocean Park, Washington
HENRY N. POLLACK, University of Michigan, Ann Arbor
JOAQUIN RUIZ, University of Arizona, Tucson
PETER M. SHEARER, University of California, San Diego, La Jolla
REGINAL SPILLER, Allied Energy, Texas
RUSSELL E. STANDS-OVER-BULL, Anadarko Petroleum Corporation, Billings, Montana
TERRY C. WALLACE, Jr., Los Alamos National Laboratory, New Mexico
National Research Council Staff
ANTHONY R. De SOUZA, Director
ELIZABETH A. EIDE, Senior Program Officer
DAVID A. FEARY, Senior Program Officer
ANNE M. LINN, Senior Program Officer
MARK D. LANGE, Program Officer
SAMMANTHA L. MAGSINO, Program Officer
JENNIFER T. ESTEP, Financial and Administrative Associate
NICHOLAS D. ROGERS, Financial and Research Associate
COURTNEY R. GIBBS, Program Associate
JASON R. ORTEGO, Research Associate
ERIC J. EDKIN, Senior Program Assistant
CHANDA IJAMES, Program Assistant
The drive to better understand how Earth’s climate has responded to natural and anthropogenic forcing over the geologically recent past has resulted in a plethora of observational and modeling paleoclimate studies seeking to understand climate dynamics associated with glacial and interglacial cyclicity. From these near-time paleoclimate studies the scientific community has developed a refined understanding of the complex—and often nonlinear—dynamics of the Earth’s climate system and has delineated an array of environmental and ecological impacts that have accompanied climate change over the past few thousands to hundreds of thousands of years. The knowledge gleaned from this near-time archive has been of great importance for predicting Earth’s immediate future climate. There is, however, a growing appreciation by the scientific community that the changes observed over the past few decades may lead to a degree of warming and associated climate, resource, and ecological changes well beyond those of the “icehouse” climate state in which humans evolved and currently live. Critical insights to understanding such changes are contained in the deep-time geological record that captures the response of the climate system to the full spectrum of internal and external forcings, and their feedbacks, experienced over Earth history.
There is little dispute within the scientific community that humans are changing Earth’s climate on a decadal to century timescale. This change, however, is happening within the context of geological time and geological magnitude, and thus must be evaluated and understood at a comparable scale. The fossil fuel CO2 released to the atmosphere by humans will impact the climate system for tens to hundreds of thousands of years,
because of the timescales over which the natural feedbacks in the climate system sweep CO2 from the atmosphere. Consequently, the changes to the hydrosphere, cryosphere, chemosphere, and biosphere that are occurring now and projected within this century could pale in comparison to those that are possible over the next few centuries. Furthermore, it is studies of deep-time climates that have revealed the nature of the complex network of short- and long-term processes and feedbacks that govern the global climate system. Perhaps more importantly, these studies have also revealed the potential for positive feedbacks that typically operate on century to millennial timescales but may become operative on much shorter, human timescales with continued warming. There are important lessons to be learned from the repeated inability of existing climate models to recreate the large changes in global temperature distributions and climates that can be deciphered from deep-time records of past climates that were much different than Earth’s current glacial state. Despite its potential, the deep-time geological record is undertapped scientifically, particularly because it hosts the only records of major, and at times rapid, transitions across climate states as well as records of past warming far greater than witnessed by Earth over the past few tens of millions of years but within the scope of that projected for our future.
This report is the committee’s collective assessment of both the demonstrated and the underdeveloped potential of the deep-time geological record to inform us about the dynamics of the global climate system in response to the spectrum of forcings and conditions under which it has operated. A large part of our effort was directed toward describing past climate changes and their impacts on regional climates, water resources, marine and terrestrial ecosystems, and the cycling of life-sustaining elements, emphasizing the lessons that have been learned uniquely from deep-time worlds. While revealing gaps in scientific knowledge of past climate states, we highlight a range of high-priority scientific issues with potential for major advances in the scientific understanding of climate processes. Understanding how the complex network of processes and feedbacks that make up the global climate system operates at various timescales—and over the full range of climate variability experienced through Earth’s history—is a high priority for improving projections of future climatic conditions and the impacts on the surface systems that can be anticipated with such change. To that end, we propose a research agenda—and an implementation strategy to address this agenda—that builds on the evolving cross- and interdisciplinary nature of deep-time paleoclimate science.
As the question is increasingly raised as to whether Earth could return—on a human timescale—to a greenhouse climate analogous to that of more than 35 million years ago, it is essential that science thoroughly
understands the mechanisms, triggers, and thresholds of climate change in past warmer worlds and the associated magnitudes, rates, and impacts of such change. We hope that the readers of this report share our collective enthusiasm for the richness and societal relevance of the geological record and for the exciting opportunities for enhanced knowledge provided by deep-time paleoclimatology.
The committee would like to thank the National Science Foundation, the U.S. Geological Survey, and Chevron Corporation for enabling this report through their financial support and participation in the study process. As chair, I would also like to acknowledge the committee members for the insights they brought to the table and their efforts in translating a plentitude of knowledge into lucid statements and informative figures. The process was not always linear and involved crossing multiple thresholds; but analogous to climate change, we anticipate that the outcome of the process, this report, will “impact” scientific understanding of the potential of Earth’s global climate system for change. Study Director David Feary deserves a special acknowledgment for his tireless effort and patience, aptitude for skillful persuasion, and wonderful wit—it was a privilege to work with him. The committee is also grateful for the support of National Research Council staff members Nicholas Rogers, Courtney Gibbs, and Eric Edkin.
Isabel Patricia Montañez, Chair
Committee on the Importance of Deep-Time Geologic
Records for Understanding Climate Change Impacts
This report was greatly enhanced by those who made presentations to the committee at public committee meetings and by the participants at the open workshop sponsored by the committee to gain community input—David Beerling, Ray Bernor, Karen Bice, Scott Borg, Gabriel Bowen, Robert DeConto, Harry Dowsett, Alexey Federov, Chris Fielding, Margaret Frasier, Linda Gundersen, Bill Hay, Patricia Jellison, H. Richard Lane, Tim Lyons, Thomas Moore, Paul Olsen, Mark Pagani, Judy Parrish, Martin Perlmutter, Chris Poulsen, Greg Ravizza, Dana Royer, Nathan Sheldon, Walt Snyder, Linda Sohl, Lynn Soreghan, Christopher Swezey, Robert Thompson, Thomas Wagner, Debra Willard, Scott Wing, James Zachos, and Richard Zeebe. The presentations and discussions at these meetings provided invaluable input and context for the committee’s deliberations. The provision of additional text and figures by Ron Blakey, Paul Olsen, Shanan Peters, Brad Sageman, Lynn Soreghan, Jim Zachos, and Richard Zeebe is also gratefully acknowledged.
This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their participation in the review of this report:
Ken Caldeira, Carnegie Institution of Washington, Stanford, California
Christopher R. Fielding, University of Nebraska, Lincoln
Paul E. Olsen, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York
Heiko Pälike, National Oceanography Centre, University of Southampton, United Kingdom
Christopher J. Poulsen, University of Michigan, Ann Arbor
Bradley B. Sageman, Northwestern University, Evanston, Illinois
Linda E. Sohl, NASA Goddard Institute for Space Studies, Columbia University, New York
Thomas N. Taylor, University of Kansas, Lawrence
Ellen Thomas, Yale University, New Haven, Connecticut
James C. Zachos, University of California, Santa Cruz
Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by William W. Hay, University of Colorado Museum, and Peter M. Banks, Executive Office, National Academy of Sciences, Washington, D.C. Appointed by the National Research Council, they were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.