National Academies Press: OpenBook
« Previous: Overview
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×

Introduction

Studies of historic and paleoclimate data (e. g., NRC, 1998), as well as climate model simulations (e. g., Easterling and Wehner, 2009), demonstrate that Earth’s climate system exhibits natural variability at a wide range of timescales because of both internal and external factors (see Box 2). Decadal climate variability refers to variability of regional and global climate on timescales of 10 to 30 years. 1 Longer trends (50 years or more) in observed global mean surface temperature (GMST) in the recent century largely reflect increases in anthropogenic greenhouse gases (GHGs; e. g., Bindoff et al., 2013). Decadal variability can be described as the ups and downs of the climate, which are superimposed on that trend (see Figure 1). In this way, decadal variability can accelerate or decelerate the rate of warming on shorter timescales, whereas climate change is dominated by the steady warming from increasing GHGs over the long term.

The slowdown in the GMST warming trend during the early 2000s spurred a lot of research aimed at identifying variability in observations and models, as well as attributing its mechanisms. What physical mechanisms can explain recent as well as past decadal variability? How much of the variability in recent trends in surface warming is due to internal, natural variability versus external forcing, and how does this attribution vary as a function of timescale? Given what is known today about the controls on decadal variability, what can be said about the future? Are such accelerations and slowdowns predictable? What observations, data synthesis, and improvements in climate models might be needed to provide comprehensive answers to such questions? Finally, what is the best way to measure the influence of human-emitted GHGs on the global climate? Is GMST the best

___________________

1 Participants noted that while the timescale of decadal climate variability is approximately 10-30 years, the mechanisms and drivers of this variability occur at a variety of timescales, for example, ENSO (see Box 3).

Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×

Image

FIGURE 1 This schematic illustrates natural decadal climate variability in GMST (blue), which is superimposed on the long-term forcing from GHGs (change in dotted baseline indicated with red arrows). NOTE: The normal ups and downs of natural variability are then accelerated or decelerated by the long-term warming, producing a new curve that represents the combination of natural variability and human-caused warming (maroon). SOURCE: Adapted from Gerald Meehl presentation, September 3, 2015.

metric? Regardless of the measure, what methods can best evaluate inflections in the rate of climate change?

The importance of answering these and related questions extends beyond explaining the recent slowdown in surface warming: The ability to anticipate, and eventually predict, such changes is important to decision-making. Planners and policy makers want information about decadal variability to make decisions in a range of sectors, including for infrastructure, water resources, agriculture, and energy. Furthermore, like the well-studied El Niño and La Niña interannual variations, decadal climate variability is associated with specific regional patterns of temperature and precipitation, such as heat waves, cold spells, and droughts. For example, some of the same mechanisms responsible for the recent warming slowdown may have played a role in the extended drought in the U. S. western states (e. g., Delworth et al., 2015). Clarifying the processes behind the recent slowdown in GMST rise can improve understanding and prediction of regional climate, which in turn can inform decisions that affect our society (e. g., Murphy et al., 2010).

In September 2015, the Board on Atmospheric Sciences and Climate and the Ocean Studies Board of the National Academies of Sciences, Engineering, and Medicine convened

Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×

a workshop to examine these questions (see Statement of Task in Appendix A). The workshop included a number of panels followed by open discussions, as well as breakout groups focused on specific modeling and observational challenges, and concluded with reflections on the workshop’s key messages and lessons on communicating these messages (see workshop agenda in Appendix B).

Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×

This page intentionally left blank.

Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×
Page 5
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×
Page 6
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×
Page 7
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2016. Frontiers in Decadal Climate Variability: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/23552.
×
Page 8
Next: Challenges in Examining Climate Trends »
Frontiers in Decadal Climate Variability: Proceedings of a Workshop Get This Book
×
Buy Paperback | $46.00 Buy Ebook | $36.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Many factors contribute to variability in Earth’s climate on a range of timescales, from seasons to decades. Natural climate variability arises from two different sources: (1) internal variability from interactions among components of the climate system, for example, between the ocean and the atmosphere, and (2) natural external forcings, such as variations in the amount of radiation from the Sun. External forcings on the climate system also arise from some human activities, such as the emission of greenhouse gases (GHGs) and aerosols. The climate that we experience is a combination of all of these factors.

Understanding climate variability on the decadal timescale is important to decision-making. Planners and policy makers want information about decadal variability in order to make decisions in a range of sectors, including for infrastructure, water resources, agriculture, and energy.

In September 2015, the National Academies of Sciences, Engineering, and Medicine convened a workshop to examine variability in Earth’s climate on decadal timescales, defined as 10 to 30 years. During the workshop, ocean and climate scientists reviewed the state of the science of decadal climate variability and its relationship to rates of human-caused global warming, and they explored opportunities for improvement in modeling and observations and assessing knowledge gaps. Frontiers in Decadal Climate Variability summarizes the presentations and discussions from the workshop.

  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!