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people and climate change
climate change > newsfile > big melt threatens millions, says un
Location of this document: http://www.peopleandplanet.net/doc.php?id=3024§ion=8
Big melt threatens millions, says UN
Posted: 04 Jun 2007
The futures of hundreds of millions of people across the world will be affected by declines in snow cover, sea ice, glaciers, permafrost and lake ice according to a report marking World Environment Day, June 5, 2007. The report is also highly relevant to International Polar Year which began in March.
Impacts from the loss of snow and ice are likely to include significant changes in the availability of water supplies for drinking and agriculture, rising sea levels affecting low lying coasts and islands and an increase in hazards such as subsidence of currently frozen land.
An estimated 40 per cent of the world’s population could be affected by loss of snow and glaciers on the mountains of Asia says the UN Environment Programme (UNEP) in the Global Outlook for Ice and Snow.
Similar challenges are facing countries, communities, farmers and power generators from the Alps to the Andes and the Pyrenees, says the report.
Melting ice and snow are also likely to increase hazards including avalanches and floods from the build up of potentially unstable glacial lakes. These can burst their ice and soil dams sending walls of water down valleys at a damaging rate.
Rising temperatures and the thawing of frozen land or ‘permafrost’ is triggering the expansion of existing - and the emergence of new - water
bodies in places like Siberia.
These are bubbling methane into the atmosphere with emissions so forceful they can keep holes open on the lakes’ icy surfaces even during sub zero winter months.
Methane is a powerful global warming gas and new estimates indicate that the quantities emerging from these so called thermokast lakes is up to five times higher than had previously been supposed.
Meanwhile less snow and sea ice are leading to more of the sun’s heat being absorbed by the land and the polar oceans which in turn may speed up global climate change.
These are among the ‘feedbacks’ which some experts fear could trigger even faster or more abrupt climatic changes with even wider-ranging impacts on people, economies and wildlife.
Adaptating to change
Some communities are already adapting to climate change. For example hunters in parts of Greenland are abandoning traditional dog sleds in
favour of skiffs as a result of less predictable sea ice.
A key railway line in China, built on permafrost, has been designed with special cooling technology to reduce the risks of subsidence.
However the report acknowledges that many indigenous peoples lack the financial resources and technology needed to adapt. While, many parts of the world currently remain ill prepared for the likely pace of climate change.
Achim Steiner, UNEP Executive Director, said the report on the fate of the world’s snowy and icy places in a climatically challenged world should be "cause for concern in every ministry, boardroom and living room across the world."
“The report comes in 2007, a year in which climate change came in from the cold in terms of science, likely impacts and costs. Indeed the
Intergovernmental Panel on Climate Change has concluded that the bill may be less than 0.1 per cent of global GDP a year. So overcoming the climate change challenge is the bargain of the century,” he added.
“The missing link is universal political action. Today’s report should empower the public to take their leaders to task — should encourage them to ask how much hotter it has to get before we act on a fair and forward-looking emissions reduction deal in Bali this December,” said Mr Steiner.
Helen Bjoernoey, the Norwegian Minister of the Environment, said it was particularly alarming to realise that climate change can be reinforcing process.
“As documented in the report, melting of ice and snow will in itself have severe consequences on nature and society. But it will also reduce the
reflection of sun beams from the surface of the Earth and in this way contribute to further global warming. Recent scientific findings indicate that these changes may occur at a faster rate than reflected in the IPCC 4th Assessment Report. So, there is reason for deep concern,” she said.
Norway aims to limit the global temperature increase to a maximum of 2 degrees Celsius - and would work to have this limit adopted as a framework for negotiations at this year’s Bali meeting, she said.
The ice and snow report builds on and in some areas extends the work of the IPCC. It also flags up areas in need of further scientific clarity which the IPY aims to resolve. These include the likely fate of the Antarctica and Greenland ice sheets where 98 to 99 per cent of the world’s freshwater ice on the Earth’s surface is held.
A total meltdown of the Greenland ice sheet would trigger an estimated seven metre rise in sea levels. Even just a 20 per cent melting of
Greenland and a five per cent melting of Antarctica would result in a four to five metre sea level rise.
This is a possibility over the coming centuries if greenhouse gases are not reduced in the 21st century and this might happen sooner if warming air and warming seawater continue to destabilize parts of the ice sheets.
The melting of these sheets in conjunction with those on mountain glaciers and ice caps, along with the thermal expansion of the oceans, have so far led to a sea level rise of just under 20 cm between 1870 and 2001 — with sea levels rising by just over three millimetres annually between the early 1990s and 2006.
Resolving just how much of the ice may melt has direct consequences for people living in low lying areas and islands. Based on today’s population a one-metre sea level rise would, without adaptation measures, expose some 145 million people to flooding with Asia most affected.
Areas of concern include many small islands and populations living in the mega deltas of the Ganges-Brahmaputra, the Mekong and the Nile in Africa. Low lying Bangladesh is singled out as a country of particular concern.
The overall economic costs to communities, livelihoods, industry and infrastructure could be nearly $950 billion under a one-metre sea level rise scenario.
Joan Eamer of UNEP Grid-Arendal in southern Norway said the report was unique, because it brings together "all the different forms of ice and snow that occur in the world — collectively known as the crysphere - and links them to the climate, to nature and to people both now and in the future”.
Depending on snow
Seasonal snow cover is the main source of runoff in the dry season in many mountain regions — globally over a billion people depend on it for their water supplies for domestic, agricultural and industrial uses.
Snow is also economically important for winter sports, agriculture and animal husbandry such as reindeer herding and survival of caribou. Snow
that has melted and refrozen into ice can become too hard for these animals to graze for their key food source — lichens.
“There have been catastrophic declines in the Peary caribou on Arctic islands of North America and they are now considered endangered. The
formation of ice layers, following rain during the winter... has been identified as the chief cause of the declines,” says the report.
Satellite monitoring shows that, since the late 1960s, snow cover in the Northern Hemisphere has been decreasing by 1.3 per cent per decade.
The Western United States, particularly in the spring in the Pacific North West, is among the regions seeing the biggest decrease. Here the ‘depth’ or quantity of water from snow melt has fallen by between 50 per cent and 75 per cent over recent decades.
Melting of snow in the Rocky Mountains of British Columbia form the headwaters of the Columbia River. It supplies water for larges areas of western Canada and north-west United States including for important irrigation and hydroelectric schemes.
The report says unchecked climate change will aggravate the changes. For example a 2 degree C temperature rise in the Cascade Range of mountains of the Pacific North West of the United States could “reduce temperate snow cover by over 20 per cent”.
Similar impacts are likely in the Andes, the Alps and the Pyrenees which in turn will decrease summer water run off. For every one degree C rise in temperature, the snow line is predicted to move up the mountains — by 120 metres in Chile for example and by 150 metres in the Alps.
The report notes that the declines in snow will not be uniform with some climate models indicating reductions of snow of between 60 per cent and 80 per cent in middle latitudes like Europe by the end of the century — but increases in Siberia and the Canadian Arctic by the same time as a result of increased precipitation.
Changes in patterns of snow are likely to impact on tourism and recreation including skiing and snowmobiling.
Methane bubbling lakes
Permafrost or frozen ground is not only important for the stability of buildings, roads and railways. These soils also contain large quantities of ancient greenhouse gases which could be released into the atmosphere as a result of widespread thawing.
“The upper part of permafrost in boreal and arctic ecosystems is estimated to contain around 750 to 950 gigatonnes of organic carbon,” says the report. Currently there are around 750 gigatonnes of organic carbon in the atmosphere.
Some models predict that permafrost could, by the end of the century, be thawing in “practically all areas south of the Brooks Range in Alaska and in most of a sub artic Canada. In Russia the most severe permafrost degradation is projected for northwest Siberia and the European north. Almost all permafrost along the southern coasts of Greenland will be thawing by the end of the 21st century”.
The area of permafrost in China is expected to decline by 30 per cent to 50 per cent during this century.
Some countries are already adapting to cope with projected permafrost thawing. The design of the Qinghai-Tibet railway already factors in the likely impact of a 2.6 degree C temperature rise by incorporating cooling techniques.
“The impacts of climate changes on stability will also need to be considered in the design of the proposed China-Russia oil pipeline,” says the report.
The report also flags up the curious case of lakes forming in places like Siberia as a result of the thawing of ice rich permafrost. Bubbles of
methane, estimated to be up to 43,000 years-old, are being released to the atmosphere.
In Siberia, the amounts of methane being released maybe five times higher than was previously supposed.
“If significant permafrost warming and thawing occurs as projected, tens of thousands of teragrams of methane could be emitted from lakes — an amount that greatly exceeds the 4,850 teragrams of methane currently in the atmosphere,” says the report.
Shrinking sea ice
Sea ice is important in relation to ocean circulations such as the Gulf Stream and is also important for the food chain and also for wildlife such as polar bears and walruses as well as fisheries.
Overall the extent of sea ice in the north has decreased by 2.5 per cent per decade in March and close to nine per cent in September over the past quarter century. At just over 10.5 per cent, the biggest decline has been in the Greenland Sea.
In Antarctica the trend is less clear cut with a weak ‘non-significant’ overall increase in its extent, for example, in the Ross Sea of 4.8 per cent per decade but a decrease in, for example, the Bellingshausen Sea of 5.3 per cent per decade.
Sea ice extent in both polar regions is expected to decline by a quarter by 2100 with the Arctic largely ice-free in the summer by the same date. But the report also points to possible abrupt changes or ‘tipping points’ that could bring an ice-free Arctic in the summer months forward by 60 years.
The Northern Sea Route along the Siberian coast is currently navigable for 30 days but this could increase to 120 days during the century - a new economic opportunity for the region - but one that will require careful environmental management as access to oil and gas fields and fisheries increases.
More shrinking glaciers
Many glaciers are already receding in response to climate change. The report says that a three degree C rise in summer air temperatures could see the Alps lose about 80 per cent of their glacier cover.
Heavily glaciated areas like Argentina and Chile’s Patagonia region and the St Elias Mountains in Alaska could see the collapse of these ice bodies.
The formation of lakes as a result of melting glacier and the risks of glacial lake outburst floods (GLOFs) is also highlighted. Such lakes have potential to release up to 100 million cubic metres of water at flows approaching 10,000 cubic metres a second down vulnerable valleys.
Mountain regions at risk include the Himalayas, Tien Shan and the Pamirs of Tajikistan but also the Andes and the European Alps.
In July 1998 a GLOF in the Shahimardan valley of Kyrgyzstan and Uzbekistan killed over 100 people. Another in August 2002 in the Shakhdara valley of the Tajik Pamir mountains claimed 23 lives.
Meanwhile in Asia the lives of some 2.4 billion people — 40 per cent of the current global population — are influenced by the summer melt waters of glaciers in the Himalayas-Hindu Kush, Kunlun Shan, Pamir and Tien Shanan mountain regions.
These glaciers could shrink by between just over 40 per and up to around 80 per cent by 2100 under current climate models with some mountain ranges completely devoid of glacial coverage.
Rivers at risk include the Syr Darya, Amu Darya, Indus, Ganges, Brahmaputra, Yangtze and Huang He or Yellow river where some 1.3 billion people could be at increased risk of water shortages and many more at risk of losing irrigation water for crops as well as disruptions to industry and
African glaciers have lost over 80 per cent of their area indicating major changes in climate and other phenomena such as rainfall.
Rivers and lakes
Freshwater ice is an important component of many river and lakes in the Northern Hemisphere including North America’s Red River; Finland’s Lake Kallavesi and Tornionjoki river and the Angara river in south east Siberia.
Long term records indicate that rising air temperatures in the autumn and spring have produced a 10 to 15 day delay in ‘freeze up’ and a similar advance in break up.
Models indicate that continued climate change might change the timing and magnitude of spring melting affecting spring ‘ice jam’ flooding in
communities. Climate change might actually reduce these dramatic events in the far north — but this could lead to the extensive wetlands on Arctic river deltas drying out and turning to shrubland.
There is also concern over the impacts on fish and other biodiversity and links between transport and indigenous peoples. Currently many remote communities use frozen lakes and rivers as routes to traditional hunting, fishing and trapping areas or for accessing larger human settlements.
The Global Outlook for Ice and Snow is available at www.unep.org/geo/geo_ice
The book is available for purchase at www.earthprint.com priced US$40.