By Keppenne, Christian L.; Dettinger, Michael D. et al. | Journal of the American Statistical Association, June 1994 | Go to article overview


Keppenne, Christian L., Dettinger, Michael D., Ghil, Michael, Journal of the American Statistical Association

Like many recent studies of instrumental climatological records (see, for example, Ghil and Vautard 1991; Jones et al. 1986; Karl 1985; and Karl, Heim, and Quayle 1991), Handcock and Wallis's work aims to identify possible variations of the earth's climate over the last century. Their use of a rigorous Gaussian random field (GRF) approach to model surface air temperatures over part of the northwestern United States is new. The stochastic structure of time series of winter average temperatures at 88 sites belonging to the U.S. Historical Climatology Network (HCN) is characterized by this approach, and a temporally stable spatial structure--with little evidence of temporal dependence--is found. As a corollary, they derive posterior distributions of the areal mean temperature over time. This application of their random model indicates that, given a scenario of a gradual increase of 5[degrees]F over 50 years, it would take 30-40 more winters of data over this region, for the change to become discernible from natural temperature variations.

The limited geographical area and short time span (50 years) considered are dictated by the nature of the HCN data and GRF model. They restrict somewhat the scope of Handcock and Wallis's conclusions, without invalidating the approach chosen. The analysis is confined to a region extending longitudinally from eastern Montana through the Dakotas and meridianally from northern Nebraska to the Canadian border. This area was chosen because experiments with atmospheric general circulation models (GCM's; see, for example, Schlesinger and Mitchell 1987) agree in unanimously predicting future warming in the corresponding latitude belt, on the one hand, and because the data are relatively homogeneous over it, on the other. But temperature variations observed in this region are not representative of global variability or even of changes over the entire North American region. Attempting to draw general conclusions, applicable to the assessment of global warming, may not have been Handcock and Wallis's prime objective, and their approach seems appropriate for studying the time evolution of the areal-mean temperature over the region in question.

In the remainder of this discussion, we present an alternative approach that is well suited for the study of inhomogeneous temperature data over regions larger than the correlation length scale of interannual and interdecadal climatology, which is of the order of several thousands of kilometers. Analysis of larger spatial scales would presumably permit inferences as to what part of the long-term signal is regional and what part characterizes larger areas (Peixoto and Oort 1984). Moreover, most temperature changes over the last century have been confined to a relatively short period between 1910 and 1940 (Ghil and Vautard 1991), which predates the time interval studied by Handcock and Wallis.

Over the past half century, the characterization of the earth's climate has shifted from climatology to climate dynamics, from a description of the climatological mean--with random fluctuations about it--to a treatment of the climate system as a forced nonlinear oscillator responding dynamically to various deterministic and random forces, active over a wide range of time scales (Ghil and Childress 1987). When deviations from the time or space mean of some arbitrarily long interval are the focus of a climatological characterization, longer-period phenomena can be perceived as trends even though they may be purely periodic. A more realistic approach could be to shift attention to shorter-period phenomena of which several cycles are present within a given record. To a reasonable approximation, the theory of nonlinear dynamical systems allows us to linearize the system about its time mean over some long interval, to study variability over the shorter time scales, as forcing mechanisms at very different time scales are uncoupled. Results for the shorter time scales provide insights to eventually model the dynamics on the longer time scales. …

The rest of this article is only available to active members of Questia

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Cite this article

Cited article

Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25,

Note: primary sources have slightly different requirements for citation. Please see these guidelines for more information.

Cited article



Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25,

    New feature

    It is estimated that 1 in 10 people have dyslexia, and in an effort to make Questia easier to use for those people, we have added a new choice of font to the Reader. That font is called OpenDyslexic, and has been designed to help with some of the symptoms of dyslexia. For more information on this font, please visit

    To use OpenDyslexic, choose it from the Typeface list in Font settings.

    OK, got it!

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Author Advanced search


    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.