Climate Change
Climate Change Indicators in the United States
The Earth’s surface contains many forms of snow and ice, including sea ice, lake and river ice, snow cover, glaciers, ice caps and sheets, and frozen ground. Together, these features are sometimes referred to as the “cryosphere,” a term for all parts of the Earth where water exists in solid form.
Snow and ice are an important part of the global climate system. Because snow and ice are highly reflective, much of the sunlight that hits these surfaces is reflected back into space instead of warming the Earth. The presence or absence of snow and ice affects heating and cooling over the Earth’s surface, influencing the planet’s energy balance.
Climate change can dramatically alter the Earth’s snow- and ice-covered areas. Unlike other substances found on the Earth, snow and ice exist relatively close to their melting point and can change from solid to liquid and back again. As a result, prolonged warming or cooling trends can result in observable changes across the landscape as snow and ice masses shrink or grow over time.
Changes in snow and ice cover, in turn, affect air temperatures, sea levels, ocean currents, and storm patterns. For example, melting polar ice caps add fresh water to the ocean, increasing sea level and possibly changing currents that are driven by differences in temperature and salinity.
Because of their light color, snow and ice reflect more sunlight than open water or bare ground, so a reduction in snow cover and ice causes the Earth’s surface to absorb more energy from the sun.
Changes in snow and ice could not only affect communities and natural systems in northern and polar regions, but also have worldwide implications. For example, thawing of frozen ground and reduced sea ice in the Arctic could affect biodiversity on local and global scales, leading to harmful effects not only on polar bears and seals, but also on migratory species that breed or feed in these areas. These same changes could affect human societies in several ways, such as by compromising food availability. For communities in Arctic regions, reduced sea ice could increase coastal erosion and exposure to storms, threatening homes and property, while thawing ground could damage roads and buildings. Reduced snow cover could diminish the beneficial insulating effects of snow for vegetation and wildlife, while also affecting water supplies, transportation, cultural practices, travel, and recreation for millions of people.