The committee was tasked with developing a technical document proposing an illustrative suite of indicators, measurements (and the locations around the globe where the measurements can be applied), and metrics that are most important for understanding global climate change and provide insights into environmental sustainability issues (Box 1-1 for definitions). This information could be useful in the consideration of a coordinated climate observing strategy. The report is not a comprehensive analysis of all of the human-environment interactions that are stressed by climate change. Instead, it focuses on developing a representative set of measurable metrics that are likely to be affected by climate change over the next 20-25 years (rather than the longer term or highly uncertain stresses of the next century) and that, when taken together, can be used as indicators of environmental sustainability. Moreover, there is a wide array of social issues that are beyond the charge of the committee and therefore were not considered for extensive integration into the list of metrics: comprehensive measures of vulnerability, resilience, and adaptation; national security; and political and social contexts of decisions under conditions of uncertainty. The committee identifies potential metrics and draws lessons about their uses, but, following the guidance in the statement of task, it does not make recommendations.
Definitions of Key Terms
Ecosystem services: The many life-sustaining benefits we receive from nature—clean air and water, fertile soil for crop production, pollination, and flood control. They are important to our health and well-being, yet they are limited and often taken for granted as being without cost.
Environmental sustainability (in the context of a changing climate): The ability of an environmental system to maintain processes, functions, biodiversity, and productivity. This is particularly relevant in a changing climate and under additional influences resulting from the possible implementation of strategies to mitigate and/or adapt to climate change.
Indicator: A selected subset of metrics that is judged helpful for projecting future performance of a system.
Measurement: A quantitative, physical attribute.
Metric: A category that reflects a combination of individual measurements and that can be used to provide a large-scale view of a system and gauge system performance. It may be quantitative or qualitative (NRC, 2005).
Resilience: A capability to anticipate, prepare for, respond to, and recover from significant threats with minimum damage to social well-being, the economy, and the environment.
Vulnerability: The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes.
As a technical document, this report is intended to be used by analysts in the intelligence community, as well as researchers, as they delve more deeply into climate change and its ramifications worldwide (Box 1-2). The process of prioritizing the metrics (described in Chapter 3) was developed with this audience in mind. The types of measurements mostly focused upon are generally those obtained by remote sensing; however, there are some cases for which in situ measurements are particularly useful. The committee recognizes that the metrics suggested in the report are not perfect, but hopes they will serve as a catalyst for further thinking.
As an informational foundation for this study, eight groups (“topical panels”) were assigned the task of developing lists of measurements, metrics, and indicators of environmental sustainability in their respective areas of expertise. Two workshops were held, which included invited presentations and breakout sessions, from which preliminary lists and supporting information were generated. (See Appendix B for more information on the guidance provided to the panels. Note that the format of the tables and definitions evolved over time as the committee did its work.) Committee judgment formed the basis from which the tables in Chapter 3 were constructed.
Background for This Study: Science in Support of the Intelligence Community’s Work on Climate Change
During the 1990s, a program known as MEDEA brought together environmental scientists and members of the intelligence community to further understanding of environmental change. Prominent scientists were granted security clearances to participate in a review of national security systems, data, and archives with the objective of identifying scientifically relevant materials. Through analyses of classified data and systems, the scientists worked with the intelligence community and the White House on several emerging environmental issues, including global climate change. The MEDEA program helped justify the eventual declassification and release of scientifically important, high-resolution imagery from the archives, which were subsequently used by the scientific research community to complement publicly available, but less detailed, imagery of several environmental systems. These data have since been applied across a broad spectrum of the environmental sciences including oceanography, geologic
processes, ecology, forestry, desertification, land use and agriculture, natural disasters and, more recently, Arctic sea-ice processes (NRC, 2009a).
In the mid-1990s, MEDEA scientists and their colleagues in the intelligence community instituted a program to ensure continued collection of classified imagery at environmentally sensitive locations around the globe. The purpose of the program, known as the Global Fiducials Project, was to ensure the collection of classified imagery of areas vulnerable to environmental shifts and damage that, when monitored with detailed capability, provide early warning of environmental stresses. The understanding was that the images would be held in trust in classified archives, with the eventual goal of declassification and release to the broader scientific community for research purposes. Initially, data were collected at approximately 285 sites globally. The MEDEA program was disbanded in 2001 when the Administration changed and different priorities were instituted. By 2005, only a small number (about 75) of legacy observations continued, mostly in North America.
The utility of the fiducials project rested on the premise that certain locations around the world could serve as “pulse points” that, when monitored with detailed capability, could provide early warning of environmental stresses. The program was conceived as the nation’s intelligence community began to weigh the national security implications of climate change and to take steps to apply its unique monitoring capabilities to further the understanding of climate change. The data obtained have proven invaluable for a wide range of climate-related scientific studies.
CLIMATE CHANGE AS AN ENVIRONMENTAL STRESSOR
The human-environment system includes a complex set of nonlinear interactions between the natural world and human society (e.g., see reports such as Ecosystems and Human Well-being: General Synthesis [MEA, 2005], Ecological Impacts of Climate Change [NRC, 2008a], and Climate Change 2007: Working Group II: Impacts, Adaption and Vulnerability [IPCC, 2007a]. Of the many environmental stressors having impacts with human ramifications, climate change is perhaps the most significant. By the middle of this century, the human population is expected to grow to about 9 billion, resulting in increased demands for energy, food, water, health, and shelter just to maintain standards of living, much less to increase them (Figure 1-1). This growing demand for resources will lead to substantially less resilience in the Earth system. Any shortfalls or disruptions in the supply of critical ecosystem services will be magnified throughout various processes within the Earth system.
The interconnections among systems and the linkages between global- and local-scale processes, and between short and long timescales, greatly complicate both research and observing systems. Moreover, it is difficult for governments, businesses, and individuals to develop climate-adaptive strategies for an uncertain future. For example, consider wind energy systems, which involve the fundamental engineering challenge of matching wind energy supply patterns with transmission capabilities and electrical demand patterns. All of these factors are complicated by climate, political, and economic issues. How will the economics of wind energy systems evolve as wind patterns are altered by climate change, or if there are changes in government-mandated renewable energy portfolios or in county land-use and zoning restrictions in rural areas? Society needs information and tools to assess vulnerabilities to environmental stressors, and in particular climate change, both in the short term and the long term to increase resilience in human and Earth systems.
THE COMMITTEE’S CHALLENGE
Many organizations have proposed potential climate change indicators. Examples include the Global Climate Observing System’s Essential Climate Variables,2 the
National Aeronautics and Space Administration’s Key Indicators of Climate Change,3 the National Oceanic and Atmospheric Administration’s Arctic Indicators,4 the National Climatic Data Center’s Global Climate Change Indicators,5 Indicators of Climate Change in California,6 the Environmental Protection Agency’s Climate Change Indicators in the United States,7 and the International Geosphere-Biosphere Programme’s Climate Change Index.8
These published sets of climate change indicators generally highlight the fundamental physical science of climate processes and their associated impacts on the natural world. Observations such as these will continue to be important. But traditional climate change indicators are typically selected to tell us how the climate is changing and provide relatively little insight into the human dimensions of climate change. However, in this report, the committee identifies climate change metrics, that, when taken together, might provide advance warning of climate-related changes and their impacts on environmental sustainability. Furthermore, they can aid the scientific community in testing and developing models and hypotheses about how Earth and human systems are changing.
This perspective is especially relevant for political and economic planning and decision making rather than for specific climate forecasting. Understanding the range of possibilities and probable disruptive events will lead to an improved process of risk assessment with regard to the impacts of climate change. The linkage between risk and impact is another essential component of the indicators: Unlikely, high-impact events can be as important as likely, moderate-impact events.
The intellectual foundation for the committee’s charge is the Millennium Ecosystem Assessment (MEA), which documents the rationale for why the committee looked beyond simply identifying indicators that emphasize the fundamental physical science of climate change (Box 1-3). The MEA describes the dependence of human well-being on healthy ecosystems as well as the global loss of ecosystem services. Ecosystem services are the benefits that ecosystems provide, and they result from interactions of plants, animals, and microbes with one another and with the environment. The delivery of ecosystem services is affected by changes in biodiversity, habitat fragmentation and conversion, alterations to biogeochemical cycles, and climate change. The inextricable linkage between human civilization and the ecosystem services upon which it relies is at the core of environmental sustainability.
The Millennium Ecosystem Assessment
The Millennium Ecosystem Assessment (MEA) reports evaluate the condition of and trends in the world’s ecosystems, the services they provide, and the options to restore, conserve, or enhance their sustainable use. The four main findings are as follows:
This committee’s fundamental challenge was incorporating consideration of environmental sustainability into the indicators concept. Sustainability is an often-used term with multiple, relatively subjective definitions, and its use in a report such as this one can be confusing. At its core, the term “environmental sustainability” involves a union among environment, society, and economics. The sustainability of human and Earth systems is in large part a function of the vulnerability and resilience to system threats. Moreover, just as with natural ecosystems, human systems have the capacity to adapt and evolve in response to unforeseen changes in the environment, but this capacity is limited in terms of time and space as well as by the intensity of the change. For example, a severe hurricane may disrupt a local region of the U.S. Gulf Coast for a year or two, but a repeated series of severe hurricanes in the region would likely lead to a permanent redistribution of people and infrastructure. Thus, it is the nature of the disruptive events (e.g., their intensity, frequency, extent) that can overstress society’s
resilience. We focused on those environmental processes that would likely be in this “disruptive” scale.
The committee sorted through the many possible indicators of climate change and identified metrics within key sectors that may give advance warning of climate-related changes and their impacts. The overarching aim was to provide a conceptual foundation for the selected observations that integrate across a wide range of both local- and global-scale observing systems in order to deliver useful information. The committee would like to emphasize that the discussion, findings, and conclusions found in this report should be considered exploratory rather than definitive.
The premise behind the committee’s charge is that climate change is a threat to the sustainability of various components within the Earth system (cryosphere, land-surface, hydrology, atmosphere, and oceans), and, consequently, to human systems. In response to the charge, the committee viewed climate change metrics through a “sustainability filter”—that is, the committee decided that for a metric to be deemed an indicator of environmental sustainability it must inform how climate change affects the five domains of human vulnerability: water, food, energy, health, and shelter. Chapter 2 explores examples of these concepts in more depth and draws on examples of the metrics in Chapter 3. Tables (divided by topical area) of these metrics and others are found in Chapter 3. These tables also include measurements, locations, and statements as to how the proposed metrics can be used as indicators of environmental sustainability. The report concludes in Chapter 4 with final thoughts.