Snow and climate change
Sebastian Balzer
Snow worldwide
When looking at earth from space, one thing is obvious. The snow-covered surface on the northern hemisphere
varies from 2 million to 45 million square km. Even the rotation of the earth is influenced by these snow masses. Not
the weight but the size of the snow-covered surface is important for the climate system.
Nearly half of the land surface on the northern hemisphere is covered by snow in winter. This means that large areas
which normally would be dark, turn white. Snow-covered areas reflect approximately 80 to 90 percent of the
incoming sunlight while dark areas only reflect about 10 to 20 percent. These areas act like a large mirror that can’t
be warmed by the sun which leads to colder temperatures. Because of these colder temperatures the snow melting
is slowed down. Simulations of global climate models show that the average annual temperature in polar latitudes
would be 5 to 10 degrees Celsius higher without snow.
In addition, the area of permafrost soil would increase by 70 percent despite the warmer temperatures because the
isolating snow cover is missing and the soil cools down. This can have a noticeable impact: The frozen soil can’t
absorb melting snow and rain as well as soil without permafrost. This will increase the danger of floods and slow
down the evolution of wildlife. The weather could also be affected because the atmospheric circulation changes with
the snow-covered surface.
Snow as a reservoir
Snow is nothing different from rain in solid state which is going to melt later. This delayed water delivery provides
balanced groundwater tables and soil moisture in a lot of areas even during warmer periods. A sufficient soil
moisture is very important for a balanced climate because evaporation as well as the white of snow-covered areas
prevent warmer soil. Thereby the soil doesn’t dry out as quickly and droughts cause less damage. The snow reserves
in higher locations do not only provide a reservoir for millions of people downstream but also act as a supplier for
groundwater and soil moisture.