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Snow
Mean monthly snow-cover extent in the Northern Projected changes in amount of snow cover will affect
Hemisphere has declined at a rate of 1.3 per cent per the structure of ecosystems.
decade over the last 40 years with greatest losses in the Snow cover is a major influence on climate due to its
spring and summer. high reflectivity of sunlight and its insulating proper-
Major reductions in snow cover are projected for mid- ties. Decreases in snow-cover extent will act as a posi-
latitudes by the end of this century. Parts of the Ca- tive feedback to global warming by changing the re-
nadian Arctic and Siberia are projected to receive in- flectivity of the land surface.
creased snow fall. Changes in snow cover have a dramatic impact on wa-
Air temperatures are projected to continue increasing ter resources. Snow in mountain regions contributes
in many mountainous regions, which will raise snow to water supplies for almost one-sixth of the world’s
lines and cause other changes in mountain snow cover. population.
Snow is an important ecological factor. Increased fre- Changes in snow cover affect human well-being
quency of snow thaw due to rise in air temperatures through influences on water resources, agriculture,
changes the properties of snow cover, with implica- infrastructure, livelihoods of Arctic indigenous people,
tions for plants and animals that interact with snow. environmental hazards and winter recreation.
10 GLOBAL OUTLOOK FOR ICE AND SNOW