Shrinking Snow and Ice Cover

The Science Teacher, March 2011 | Go to article overview

Shrinking Snow and Ice Cover


The decreases in Earth's snow and ice cover over the last 30 years have, on average, exacerbated global warming more than models predict they should have, new research from the University of Michigan (U-M) shows.

To conduct this study, Mark Flanner, assistant professor in the Department of Atmospheric, Oceanic, and Space Sciences at U-M , analyzed satellite data showing snow and ice during the last three decades in the Northern Hemisphere-which holds the majority of the planet's frozen surface area. The research is published online in Nature Geoscience.

Snow and ice reflect light and heat from the Sun back into space, causing an atmospheric cooling effect. But as the planet warms, more ice melts and, in some cases, less snow falls, exposing additional ground and water that absorb more heat, which amplifies the effects of warmer temperatures. This change in reflectance contributes to what is called albedo feedback,, one of the main positive feedback mechanisms that adds fuel to the planet's warming trend.

"If the Earth were just a static rock, we could calculate precisely what the level of warming would be, given a perturbation to the system," Flanner says. "But because of these feedback mechanisms, we don't know exactly how the climate will respond to increases in atmospheric carbon dioxide."

"Our analysis of snow and sea ice changes over the last 30 years indicates that this cryospheric feedback is almost twice as strong as what models have simulated," Flanner says. "The implication is that Earth's climate may be more sensitive to increases in atmospheric carbon dioxide and other perturbations than models predict."

[ILLUSTRATION OMITTED]

The cryosphere is the planet's layer of snow, sea ice, and permanent ice sheets. Since 1979, the average temperature in the Northern Hemisphere has risen by about 0.7[degrees]C, whereas the global average temperature has risen by about 0.45[degrees]C, Flanner says.

For every 1[]C rise in the Northern Hemisphere, Flanner and his colleagues found that an average of 0.6 fewer watts of solar radiation are reflected to space per square meter because of reduced snow and sea ice cover. In the 18 models taken into consideration by the International Panel on Climate Change, the average was 0.25 watts per square meter per degree Celsius over the same time period.

Flanner points out that the models typically calculate this feedback over 100 years-significantly longer than this study, which might account for some of the discrepancy. Satellite data only goes back 30 years.

To further put the results in context, each square meter of Earth absorbs an average of 240 watts of solar radiation. These new calculations show that the Northern Hemisphere's cryosphere is reflecting 0.45 watts less per square meter now than it did in 1979, due mostly to reduced spring snow cover and summer sea ice.

"The cryospheric albedo feedback is a relatively small player globally, but it's been a surprisingly strong feedback mechanism over the past 30 years," Flanner says. "A feedback of this magnitude would translate into roughly 15% more warming, given current understanding of other feedback mechanisms."

To avoid the worst effects of climate change, the scientific consensus is that the global average temperature should stay within 2[degrees]C of preindustrial levels. Scientists are still trying to quantify the extent to which the planet will warm as greenhouse gases accumulate in the atmosphere.

"People sometimes criticize models for being too sensitive to climate perturbations," Flanner says. "With respect to cryospheric changes, however, observations suggest the models are a bit sluggish." (University of Michigan) http://ns.umich.edu/htdocs/releases/story. php?id=8199

Wheat Resistance Genes

Many of the genes that allow wheat to ward off Hessian flies are no longer effective in the southeastern United States, according to the U. …

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

Sign up now for a free, 1-day trial and receive full access to:

  • Questia's entire collection
  • Automatic bibliography creation
  • More helpful research tools like notes, citations, and highlights
  • A full archive of books and articles related to this one
  • Ad-free environment

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
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

Shrinking Snow and Ice Cover
Settings

Settings

Typeface
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?

Help
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

    Style
    Citations are available only to our active members.
    Sign up now 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, http://www.questia.com/read/27419298.

    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.

    For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

    Already a member? Log in now.