National Academies Press: OpenBook

Advancing the Science of Climate Change (2010)

Chapter: Appendix D: Uncertainty Terminology

« Previous: Appendix C: Panel on Advancing the Science of Climate Change: Biographical Sketches
Suggested Citation:"Appendix D: Uncertainty Terminology." National Research Council. 2010. Advancing the Science of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12782.
×

APPENDIX D
Uncertainty Terminology

In assessing the state of knowledge about climate change, scientists have developed a careful terminology for expressing uncertainties around both statements of fact about a current situation (for example, “most observed warming can be attributed to human action”) and statements about the likelihoods of various future outcomes (for example, “sea level could rise by several feet by 2100”). The IPCC, in particular, has devoted serious debate and discussion to appropriate ways of expressing and dealing with uncertainty around such statements (Moss and Schneider, 2000), and all recent IPCC assessments have adopted a set of terminology to describe the degree of confidence in conclusions (see, e.g., Manning et al., 2004). In estimating confidence, scientific assessment teams draw on information about “the strength and consistency of the observed evidence, the range and consistency of model projections, the reliability of particular models as tested by various methods, and, most importantly, the body of work addressed in earlier synthesis and assessment reports” (USGCRP, 2009). It is easier to employ precise uncertainty language in situations where conclusions are based on extensive quantitative data or models than in areas where data are less extensive, important research is qualitative, or models are in an earlier stage of development. Statements about the future are also generally more uncertain than statements of fact about observed changes or current trends.


Table D.1 shows the language adopted by the IPCC to describe confidence about facts or the likelihood that a statement is accurate. The U.S. Global Change Research Program’s recent assessment report on Global Climate Change Impacts on the United States(USGCRP, 2009) uses similar language. In this report, Advancing the Science of Climate Change, when we draw directly on the statements of the formal national and international assessments, we adopt their terminology to describe uncertainty. However, because of the more concise nature and intent of this report, we do not attempt to quantify confidence and certainty about every statement of the science.

Suggested Citation:"Appendix D: Uncertainty Terminology." National Research Council. 2010. Advancing the Science of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12782.
×

TABLE D.1 Language Adopted by the IPCC to Describe Confidence About Facts or the Likelihood of an Outcome

Terminology for Describing Confidence About Facts

Very high confidence

At least 9 out of 10 chance of being correct

High confidence

About 8 out of 10 chance

Medium confidence

About 5 out of 10 chance

Low confidence

About 2 out of 10 chance

Very low confidence

Less than 1 out of 10 chance

Terminology for Describing Likelihood of an Outcome

Virtually certain

More than 99 chances out of 100

Extremely likely

More than 95 chances out of 100

Very likely

More than 90 chances out of 100

Likely

More than 65 chances out of 100

More likely than not

More than 50 chances out of 100

About as likely as not

Between 33 and 66 chances out of 100

Unlikely

Less than 33 chances out of 100

Very unlikely

Less than 10 chances out of 100

Extremely unlikely

Less than 5 chances out of 100

Exceptionally unlikely

Less than 1 chance out of 100

SOURCE: IPCC (2007a).

Suggested Citation:"Appendix D: Uncertainty Terminology." National Research Council. 2010. Advancing the Science of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12782.
×
Page 491
Suggested Citation:"Appendix D: Uncertainty Terminology." National Research Council. 2010. Advancing the Science of Climate Change. Washington, DC: The National Academies Press. doi: 10.17226/12782.
×
Page 492
Next: Appendix E: The United States Global Change Research Program »
Advancing the Science of Climate Change Get This Book
×
Buy Paperback | $49.95 Buy Ebook | $39.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Climate change is occurring, is caused largely by human activities, and poses significant risks for--and in many cases is already affecting--a broad range of human and natural systems. The compelling case for these conclusions is provided in Advancing the Science of Climate Change, part of a congressionally requested suite of studies known as America's Climate Choices. While noting that there is always more to learn and that the scientific process is never closed, the book shows that hypotheses about climate change are supported by multiple lines of evidence and have stood firm in the face of serious debate and careful evaluation of alternative explanations.

As decision makers respond to these risks, the nation's scientific enterprise can contribute through research that improves understanding of the causes and consequences of climate change and also is useful to decision makers at the local, regional, national, and international levels. The book identifies decisions being made in 12 sectors, ranging from agriculture to transportation, to identify decisions being made in response to climate change.

Advancing the Science of Climate Change calls for a single federal entity or program to coordinate a national, multidisciplinary research effort aimed at improving both understanding and responses to climate change. Seven cross-cutting research themes are identified to support this scientific enterprise. In addition, leaders of federal climate research should redouble efforts to deploy a comprehensive climate observing system, improve climate models and other analytical tools, invest in human capital, and improve linkages between research and decisions by forming partnerships with action-oriented programs.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!