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Mass balance of Maliy Aktru Glacier, Russian Altai 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
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Northern Hemisphere snow-cover extent anomalies 1966-2005 Northern Hemisphere snow-cover extent anomalies 1966-2005
Data from satellite monitoring from 1966 to 2005 show that mean monthly snow-cover extent in the Northern Hemisphere is decreasing at a rate of 1.3 per cent per decade. For the calendar year of 2006 average snow-cover extent was 24.9 million km2, which is 0.6 million km2 less than the 37-year average. In the Northern Hemisphere, spring and summer show the strongest decreases in snow-cover extent. Satellite observations of snow-cover extent show a...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Projected temperatures in the 21th century Projected temperatures in the 21th century
Projected Arctic annual land temperature increases for the first half of the 21st century relative to the average temperature for 1980–99. The average of the IPCC models (the blue line) shows an increase of 3ºC by 2050. The averages of the runs from each of the 12 models show increases from 2–4ºC, the range of uncertainty in these model projections.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Temperatures over previous centuries from various proxy records Temperatures over previous centuries from various proxy records
Evidence from tree rings and other temperature proxies suggests that during the previous 500 years global temperatures were 1.0ºC cooler than those of the 20th century during a period roughly from 1300 to 1870 – known as the Little Ice Age. While overall temperatures during the Little Ice Age were cooler than now, there was much year-to-year variability and some warm periods. The coldest part of the Little Ice Age, from 1645 to 1715, was also a t...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Antarctica, showing rates of surface-elevation change derived from satellite radar-altimeter measurements Antarctica, showing rates of surface-elevation change derived from satellite radar-altimeter measurements
The figure shows rates at which the ice-sheet mass was estimated to be changing based on radar-altimeter data (black), mass-budget calculations (red), and satellite gravity measurements (blue). Rectangles depict the time periods of observations (horizontal) and the upper and lower estimates of mass balance (vertical). Measurements by satellite techniques based on gravity indicate mass loss at a rate of 138 ± 73 billion tonnes per year during 200...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Trends in permafrost temperatures and active-layer thickness, Northern Tien Shan mountains Trends in permafrost temperatures and active-layer thickness, Northern Tien Shan mountains
Mountain permafrost in Central Asia occupies approximately 3.5 million square kilometers and makes up about 15 per cent of the total permafrost area in the Northern Hemisphere. The climatic variations during the 20th century and especially during the last two decades have impacted current permafrost temperatures. In the Tien Shan Mountains, Qinghai-Tibet Plateau, and western Mongolian sector of the Altai Mountains, observations over the last 30 ...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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The Cryosphere, components and world maps The Cryosphere, components and world maps
Snow and the various forms of ice - the cryosphere - play different roles within the climate system. The two continental ice sheets of Antarctica and Greenland actively influence the global climate over time scales of millennia to millions of years, but may also have more rapid effects on, for example, sea level. Snow and sea ice, with their large areas but relatively small volumes, are connected to key interactions and feedbacks at global scales...
01 Oct 2008 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Albedo of basic thick sea ice surface types Albedo of basic thick sea ice surface types
The albedo for different surface conditions on the sea ice range widely, from roughly 85 per cent of radiation reflected for snow-covered ice to 7 per cent for open water. These two surfaces cover the range from the largest to the smallest albedo on earth. Melting snow, bare ice and ponded ice lie within this range. There is a general decrease in the albedo of the ice cover during the melt season as the snow-covered ice is replaced by a mix of me...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Change in the age of ice on the Arctic Ocean, comparing September ice ages in 1988, 1990, 2001 and 2005 Change in the age of ice on the Arctic Ocean, comparing September ice ages in 1988, 1990, 2001 and 2005
The age of sea ice in the Arctic is changing, and not only the extent and concentrations. Studies show that in recent years there is a higher proportion of younger ice to older ice than was observed in the late 1980s. This analysis is based on results from a simulation using drifting buoy data and satellite-derived ice-concentration data. The darker the colour, the older the ice.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Melting ice on Mount Kilimanjaro, East Africa Melting ice on Mount Kilimanjaro, East Africa
Close to 50 per cent of the glaciers in Africa, on the Rwenzori Mountains, Mount Kenya and Kilimanjaro have disappeared, while larger glaciers – particularly on Kilimanjaro – have been fragmented. Changes in glacier area and volume are being used as indicators for global warming and climate change.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Projected reduction in snow 2080-2100 Projected reduction in snow 2080-2100
Using one specific climate change model (ECHAM5) and the SRES A2 emission scenario (run 2) the projected loss of snow amounts to decreases of 60–80 per cent in monthly maximum snow water equivalent over most middle latitudes by the end of this century. The largest decreases are projected over Europe, while the model projects increases are in the Canadian Arctic and Siberia. Snow presents an important factor for ecosystems, water and human activit...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Ice-albedo feedback process Ice-albedo feedback process
In spring, the ice is snow-covered and there is very little open water. Most sunlight is reflected, but some is absorbed. This absorbed sunlight leads to melting, which in turn reduces the ice albedo and increases the amount of open water. This causes the albedo to further decrease, increasing the rate of heating and further accelerating melting.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Shrinking of Fedchenko Glacier in the Pamirs of Tajikistan Shrinking of Fedchenko Glacier in the Pamirs of Tajikistan
Significant loss of glaciers in Central Asia began around the 1930s, and become more dramatic in the second half of the 20th century and continue into the 21st century. Glacier area was reduced in the Tien Shan and in the Pamirs, including its largest Fedchenko Glacier. The debris-covered glacier tongue retreated by more than 1 km since 1933 and lowered by about 50 m since 1980.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Trends in spring snow cover duration for the Northern Hemisphere, 1970-2004 Trends in spring snow cover duration for the Northern Hemisphere, 1970-2004
Examination of regional trends in spring snow-cover duration from 1969–2003 using NOAA snow-cover data shows the western United States to be among the regions with the strongest decreases. This supports results from studies based on measurements on the ground. Springtime snow cover shows a decline particularly in the Pacific Northwest region of the western United States, where snow water equivalent, a common snow cover measurement equivalent to t...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Glacier shrinking on Cumberland Peninsula, Baffin Island, Canadian Arctic Glacier shrinking on Cumberland Peninsula, Baffin Island, Canadian Arctic
A new glacier inventory based on satellite data shows that the glacier cover reduced by about 22 per cent between the Little Ice Age (LIA) maximum extent and 2000. Changes in glacier area and volume are being used as indicators for climate change and global warming.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Trends in Arctic temperature, 1880-2006 Trends in Arctic temperature, 1880-2006
A history of Arctic land temperature anomalies from 1880 through 2006 is shown in this figure. The zero line represents the average temperature for 1961–1990. In the late 1800s the Arctic was relatively cold, although there is some uncertainty around these early temperature estimates. The Arctic warmed by about 0.7ºC over the 20th century. There was a warm period in the 1920s to 1940s and cold periods in the early 1900s and in the 1960s. Over th...
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Water towers of Asia - glaciers, water and population in the greater Himalayas-Hindu Kush-Tien Shan-Tibet region 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
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Glacier front variations in the European Alps Glacier front variations in the European Alps
Large Alpine glaciers have retreated continuously since the mid- 19th century, whereas steep mid-sized glaciers reacted with readvances in the 1890s, 1920s and between the 1970s and 1980s due to the somewhat cooler and wetter periods. Small glaciers feature a high annual variability with a clear shrinking trend.
01 Jun 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Trends in Antarctic tourism Trends in Antarctic tourism
Antarctic annual sea-ice extent is projected to decrease by 25 per cent by 2100, and this will bring easier access to the Antarctic continent by ship. This is likely to affect not only research, which is a main activity in a continent designated as a “natural reserve devoted to peace and science”, but also commercial activities, such as tourism. Tourism activities are expanding tremendously with the number of shipborne tourists increasing by 430 ...
01 Nov 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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Northern Sea Route and the Northwest Passage compared with currently used shipping routes Northern Sea Route and the Northwest Passage compared with currently used shipping routes
Climate models project that summer sea ice in the Arctic Basin will retreat further and further away from most Arctic landmasses, opening new shipping routes and extending the navigation season in the Northern Sea Route by between two and four months. Previously frozen areas in the Arctic may therefore become seasonally or permanently navigable, increasing the prospects for marine transport through the Arctic and providing greater access to Arcti...
01 Oct 2007 - by Hugo Ahlenius, UNEP/GRID-Arendal
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