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Glaciers
provide some of the most visible evidence of climate change. They respond
to the combination of winter snow and spring and summer temperatures.
Over the twentieth century, with few exceptions, alpine glaciers throughout
the world have retreated in response to a warming climate. The surface
area of seven Sierra Nevada glaciers has decreased dramatically since
the beginning of the twentieth century. The graph shows the fraction of
the area of these glaciers relative to the year 1903. These glaciers are
among the largest at higher elevations for which data are available. Historical
photographs and field measurements were used to estimate the surface area
of each glacier. |
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