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'Tipping Points' Multimedia for the 2007 AGU Press Event
Presenter materials from Richard Alley
Evan Pugh professor of geosciences and associate of the Earth and Environmental Systems Institute, Pennsylvania State University

Item No. 1 Credit: IPCC, 2001

Three charts showing possible causes of temperature changes
Click image for all three charts.

Presenter materials from Josefino Comiso
senior research scientist for polar oceanography, NASA's Goddard Space Flight Center

Item No. 1: The Big Sea-Ice Anomaly in 2007 -- At the end of each summer, the sea ice cover reaches its minimum extent. In 2007 that minimum extent was 27 percent less than in 2005, and 38 percent less than average.

Map of Arctic superimposed with extent of sea ice cover
Click image for enlargement.

Item No. 2: Variations in the Ice Cover -- The extent of ice that lasts year round is on the decline, now being lost at a rate of 11.4 percent per decade. Credit: NASA SVS

Line graph showing decline in sea ice cover
Click image for enlargement.
> View associated animation

Item No. 3: Trends in the Arctic Surface Temperature -- Trends in the Arctic surface temperature between 1981 and 2007 show surface temperature increases in Greenland, Eurasia and North America. The change can bee seen on this Arctic view. White indicates no temperature change and purple indicates an increase of about 3.6 degrees Fahrenheit (2 degrees Celsius) per decade.

Map showing trends in Arctic surface temperature between 1981 and 2007
Click image for enlargement.

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