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 Northern Hemisphere Snow and Ice Chart

One way of gathering information about climate change is to measure the areas of the earth covered by snow and ice, and then examine these measurements for long-term trends. But making accurate measurements of huge, irregular portions of the planet’s surface requires special methods. Satellite imagery is an ideal technique for difficult situations like this.

Satellites orbiting over the earth’s poles take numerous photographs of high-latitude areas; these photographs are then combined with maps of the area. Because snow and ice reflect light differently, areas covered by snow can be distinguished from ice-covered zones. These differences allow researchers to create precise maps of current snow and ice cover. Such maps can then be compared with maps made at other times to determine whether the extent of snow and ice cover in particular areas has been changing over the long term. Variations in snow and ice cover could reflect a number of effects of a shift in climate, including changes in both air temperatures and precipitation patterns.

Evidence indicates that polar regions are already showing the effects of climate change. Since the 1950s, Alaska has warmed by an average of 4 degrees Fahrenheit. Satellite data indicates the extent of Arctic sea ice has shown a net decrease of 2.9% per decade since 1978.

 glossary glossary terms  

Click for definitions of words used on this page:

ice core
remote sensing

View the full, printable version of the glossary.

Global Glacier Mass Balance

Northern Hemisphere Snow and Ice Chart - These daily satellite images show the earth’s northern hemisphere; areas covered by snow are white, and areas covered by ice are. Satellites fly overthe poles about twelve times each day to produce these images. Source: National Oceanic and Atmospheric Administration (NOAA), Satellite Services Division Snow and Ice Program

 questions about the data  

question Will continued global warming affect the Arctic and Antarctic regions in the same way?

email Email your own questions about this data set. 

 research connection  

To understand any long-term trend, researchers must accomplish two goals: accurate measurement at one point in time, and meaningful comparison between that measurement and others taken at different times. Real-time data—like these maps of snow and ice cover—reflect short-term measurements of today’s weather, but comparisons between images like these taken at similar times in different years can yield valuable long-term clues to climate.

 related sites  

National Oceanographic and Atmospheric Administration (NOAA), Ocean Modeling Branch - Graphs and information on the extent of sea ice.

NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS)- NASA images of snow and ice cover from space.

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