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Preponderance of Evidence

Lesson Plan 6 – Day 1

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Temperature (1880- 2005)

http://data.giss.nasa.gov/gistemp/graphs/

Year

Temperature Difference From Normal (°C)

5-year Running Average

Annual Average

Preponderance of Evidence Resource Card 2

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Muir Glacier, Alaska

NSIDC/WDC for Glaciology, Boulder, compiler. 2002, updated 2006. Online glacier photograph database. Boulder, CO: National Snow and Ice Data Center.

August 1941

August 2004

Shrinking Glaciers

Preponderance of Evidence Resource Card 3

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Source: Westerling et al. 2006

Western US area burned

Increasing Wildfire Risk

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Average Surface Temperature Changes

Average Surface Temp in 2001-2005 vs 1951-1980

Preponderance of Evidence Resource Card 5

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Keeling Curve - CO₂ Concentration

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Increasing CO₂ Concentration

IPCC, 2007

Preponderance of Evidence Resource Card 7

The Greenhouse Effect and Global Warming

Life on earth is possible because the sun’s energy warms the earth and its atmosphere. As this warmth radiates back into space, a portion is absorbed by a delicate balance of heat trapping gases in the atmosphere. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. These gases retain heat somewhat like the glass panels of a greenhouse, and act to elevate temperatures on earth. This “greenhouse effect” is a necessary natural global mechanism. Without it, the earth’s climate would be much colder and more hostile to human life.

What has changed in the last few hundred years is the additional release of carbon dioxide by human activities. Since the beginning of the Industrial Revolution, atmospheric concentrations of carbon dioxide have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. Why are greenhouse gas concentrations increasing? Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide.

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Ice Core Records

Source: Hansen, Clim.

Change, 68, 269, 2005.

Time (years)

CH4 (ppb) CO2 (ppm)

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Projected Changes in CA Summer Temperature

UCS

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2004

>9,500 ft

1900

>7,800 ft

Pika

Species Shifting

Species that are sensitive to temperature conditions can only move up the mountainside as conditions get too warm for them lower down.

In the Sierras, Pika were seen at 7,800 feet and above in 1900. By 2004, they were not seen below 9,500 feet. This trend is expected to continue.

The mountains rise as high as 12,000 feet, but the rocky hillsides where Pika live do not reach that high.

Preponderance of Evidence Resource Card 10

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Diminishing Sierra Snowpack

Percentage Remaining, Relative to 1961-1990

UCS

Preponderance of Evidence Resource Card 11