Anomalies in Northern Hemisphere Snow Cover
Snow cover extent has continued to decline and is projected to decline further, despite the projected increase in winter snowfall in some areas.
27 Oct 2009 - by Riccardo Pravettoni, UNEP/GRID-Arendal
Trends in permafrost temperatures in the central and northern Mackenzie Valley, 1984-2006
Temperature monitoring in Canada indicates a warming of shallow permafrost over the last two to three decades. Since the mid-1980s, shallow permafrost (upper 20-30 m) has generally warmed in the Mackenzie Valley. The greatest increases in temperature were 0.3 to 1°C per decade in the cold and thick permafrost of the central and northern valley. In the southern Mackenzie Valley, where permafrost is thin and close to 0°C, no significant trend in pe...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Arctic sea ice minimum extent in September 1982, 2005 and 2007
The red line indicates the median minimum extent of the ice cover for the period 1979–2000. This figure compares the Arctic sea ice extent in September for the years 1982 (the record maximum since 1979), 2005 and 2007 (the record minimum). The ice extent was 7.5 million km2 in 1982 and only 5.6 million km2 in 2005 and down to 4.3 million km2 in 2007. As has been observed in other recent years, the retreat of the ice cover was particularly pronoun...
18 Apr 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Annual cycle of light in the Northern Arctic
The Arctic is often described as a place of utter darkness or white snow in winter and of midnight sun during the summertime. In fact, there are few places on Earth where the sun displays so much variation in colour due to the low angle of the sun reflected on the mountains, snow and sky over long periods of time. North of the Arctic Circle the sun disappears during winter for days to months, depending upon latitude, leaving the sky in a palette ...
17 May 2005 - by Beatrice Collignon, Sorbonne University
Melting snow on Kilimanjaro
At the February 2001 meeting of the American Association for the Advancement of Science (AAAS), researchers reported dramatic changes in the volume of ice capping the Kibo summit of Kilimanjaro.This graphic shows the estimated extent of the glacier on Mount Kilimanjaro in 1912, and the extent of the glaciers there in 2002. The graphic also shows the decline in the total area of the ice from 1900 to 2000, with projected data to the year 2020.
17 May 2005 - by Delphine Digout, UNEP/GRID-Arendal
Rapid retreat of glaciers in the Cordillera Blanca, Peru
There is now ample evidence of a major retreat of most mountain glaciers during the last 100 years in response to widespread increases in temperature. In recent decades, the rate of glacial recession has increased tremendously.
Mountain glaciers supply moisture to mountain forests during thedry and warm seasons. With retreating mountain glaciers, the risk of forest fires increases, with a subsequent reduction of forested areas.
Smaller glaciers...
17 May 2005 - by UNEP/GRID-Arendal
Quick retreat of the Santa Rosa glacier, Peru
Several mountain glaciers now disappear at a frightening rate as in the Santa Rosa glacier of Peru.
A warmer climate often leads to increased precipitation. Much of the increased precipitation comes as rain instead of snow, mostly in the winter and to a lesser extent during the autumn and the spring. The winter rains fall over existing snow, causing increased melting.
As the ice and snow cover is reduced, the albedo of the area is reduced as we...
17 May 2005 - by UNEP/GRID-Arendal
Cooling factors
The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature. Water vapour is a greenhouse gas, but at the same time the upper white surface of clouds reflects solar radiation back into space. Albedo - reflections of solar radiation from surfaces on the Earth - creates difficulties in exact calculations. If e.g. the polar ice...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
Total global saltwater and freshwater estimates
Estimates of global water resources based on several different calculation methods have produced varied estimates. This graphic illustrates the proportions of saltwater and freshwater that make up the earth's water resources. It also shows what percentage of the world's freshwater is located in lakes and river storage; in groundwater, including soil moisture, swamp water and permafrost, and in glaciers and permanent snow cover.
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
Arctic, topography and bathymetry (topographic map)
The Arctic represents the northermost area of the World, the Arctic Ocean and the land areas that surrounds it. The region is characterized but cold temperatures, and ice and snow. The summers are short, but with long periods of daylight (midnight sun). The winters are long and cold and with periods with no sun (polar night). The Arctic Ocean is one basin that is mostly covered by sea ice, and is connected to the Pacific and Atlantic Oceans. The ...
01 Oct 2010 - by Hugo Ahlenius, UNEP/GRID-Arendal
Water towers of Asia - glaciers, water and population in the greater Himalayas-Hindu Kush-Tien Shan-Tibet region
The Himalayas–Hindu Kush, Kunlun Shan, Pamir and Tien Shan mountain ranges function as water towers, providing water to people through much of Asia. The glacier-fed rivers originating from the Himalaya mountain ranges surrounding the Tibetan Plateau comprise the largest river run-off from any single location in the world. While the mountains are homes to some 170 million people, the rivers that drain these mountains influence the lives of about 4...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
Climate change impact on mountain vegetation zones
The figure shows a comparison of current vegetation zones at a hypothetical dry temperate mountain site with simulated vegetation zones under a climate-warming scenario. Mountains cover about 20% of the Earth's continents and serve as an important water source for most major rivers. Paleologic records indicate that climate warming in the past has caused vegetation zones to shift to higher elevations, resulting in the loss of some species and ecos...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
Cooling factors
The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature. Water vapour is a greenhouse gas, but at the same time the upper white surface of clouds reflects solar radiation back into space. Albedo - reflections of solar radiation from surfaces on the Earth - creates difficulties in exact calculations. If e.g. the polar ice...
17 May 2005 - by Philippe Rekacewicz, UNEP/GRID-Arendal
Arctic, topography and bathymetry (topographic map)
The Arctic represents the northermost area of the World, the Arctic Ocean and the land areas that surrounds it. The region is characterized but cold temperatures, and ice and snow. The summers are short, but with long periods of daylight (midnight sun). The winters are long and cold and with periods with no sun (polar night). The Arctic Ocean is one basin that is mostly covered by sea ice, and is connected to the Pacific and Atlantic Oceans. The ...
01 Oct 2010 - by Hugo Ahlenius, UNEP/GRID-Arendal
Rising water levels in the Spitamen district (Tajikistan)
Sudden releases of water into the Spitamen district from Kyrgyzstan are regularly endangering the neighboring Tajik arable land downstream and villages along the river. The Tajik communities are convinced upstream Kyrgyz communities are responsible for the flooding. However, local experts suggest that increased water levels in spring the later years may also be due to increased and rapid ice and snow melt down caused by a warmer climate in the hi...
16 Mar 2006 - by Viktor Novikov, UNEP/GRID-Arendal
Mass balance of Maliy Aktru Glacier, Russian Altai
Measurements on this valley-type glacier in the North Chuyskiy Range show a slightly negative annual mass balance trend culminating in an ice loss of about 4 m water equivalent over the period 1964–2005.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal