Snow Cover Extent, approx 5 x 8 x 30" 
Embroidery on silk.

The Snow Cover Extent Climate Data Record constitutes the longest running satellite-based record of any environmental variable.

The amount of snowfall is a major indicator of climate change. Because snow is highly reflective, a vast amount of sunlight that hits the snow is reflected back into space instead of warming the planet. Without snow cover, the ground absorbs about four to six times more of the sun's energy. The presence or absence of snow controls patterns of heating and cooling over Earth's land surface more than any other single land surface feature.

The National Snow and Ice Data Center has an interesting webpage on why snow matters.