il riscaldamento globale sta avvenendo ora

["Alessandro Gimona" <agimona at hotmail.com>]

Cari tutti,
se ce ne fosse bisogno, ecco due comunicati stampa 'scientifci' che 
confermano l'urgenza di politiche volte a ridurre le emissioni di gas serra.
Le ragioni per i governi non sono mai state cosi' chiare.


Saluti
Alessandro Gimona


-------------------------------------------------------------------
NEWS FROM THE WORLDWATCH INSTITUTE
 Worldwatch News Brief 00-02


 MELTING OF EARTH'S ICE COVER REACHES NEW HIGH
 by Lisa Mastny


 The Earth's ice cover is melting in more places and at higher rates than 
at any
 time since record keeping began.  Reports from around the world compiled 
by the
 Worldwatch Institute (see data table below) show that global ice melting
 accelerated during the 1990s-which was also the warmest decade on record.

 Scientists suspect that the enhanced melting is among the first observable 
signs
 of human-induced global warming, caused by the unprecedented release of 
carbon
 dioxide and other greenhouse gases over the past century. Glaciers and 
other ice
 features are particularly sensitive to temperature shifts.

 The Earth's ice cover acts as a protective mirror, reflecting a large 
share of
 the sun's heat back into space and keeping the planet cool. Loss of the 
ice
 would not only affect the global climate, but would also raise sea levels 
and
 spark regional flooding, damaging property and endangering lives. 
Large-scale
 melting would also threaten key water supplies as well as alter the 
habitats of
 many of the world's plant and animal species.

  Some of the most dramatic reports come from the polar regions, which are
 warming faster than the planet as a whole and have lost large amounts of 
ice in
 recent decades. The Arctic sea ice, covering an area roughly the size of 
the
 United States, shrunk by an estimated 6 percent between 1978 and 1996, 
losing an
 average of 34,300 square kilometers-an area larger than the 
Netherlands-each
 year.

 The Arctic sea ice has also thinned dramatically since the 1960s and 70s.
 Between this period and the mid-1990s, the average thickness dropped from 
3.1
 meters to 1.8 meters-a decline of nearly 40 percent in less than 30 years.

 The Arctic's Greenland Ice Sheet-the largest mass of land-based ice 
outside of
 Antarctica, with 8 percent of the world's ice-has thinned more than a 
meter per
 year on average since 1993 along parts of its southern and eastern edges.

 The massive Antarctic ice cover, which averages 2.3 kilometers in 
thickness and
 represents some 91 percent of Earth's ice, is also melting. So far, most 
of the
 loss has occurred along the edges of the Antarctic Peninsula, on the ice 
shelves
 that form when the land-based ice sheets flow into the ocean and begin to 
float.
 Within the past decade, three ice shelves have fully disintegrated: the 
Wordie,
 the Larsen A, and the Prince Gustav. Two more, the Larsen B and the 
Wilkins, are
 in full retreat and are expected to break up soon, having lost more than
 one-seventh of their combined 21,000 square kilometers since late 1998-a 
loss
 the size of Rhode Island. Icebergs as big as Delaware have also broken off
 Antarctica in recent years, posing threats to open-water shipping.

 Antarctica's vast land ice is also melting, although there is disagreement 
over
 how quickly. One study estimates that the Western Antarctic Ice Sheet 
(WAIS),
 the smaller of the continent's two ice sheets, has retreated at an average 
rate
 of 122 meters a year for the past 7,500 years-and is in no imminent danger 
of
 collapse. But other studies suggest that the sheet may break more abruptly 
if
 melting accelerates. They point to signs of past collapse, as well as to
 fast-moving ice streams within the sheet that could speed ice melt, as 
evidence
 of potential instability.

 Outside the poles, most ice melt has occurred in mountain and subpolar 
glaciers,
 which have responded much more rapidly to temperature changes. As a whole, 
the
 world's glaciers are now shrinking faster than they are growing, and 
losses in
 1997-98 were "extreme," according to the World Glacier Monitoring Service.
 Scientists predict that up to a quarter of global mountain glacier mass 
could
 disappear by 2050, and up to one-half by 2100-leaving large patches only 
in
 Alaska, Patagonia, and the Himalayas. Within the next 35 years, the 
Himalayan
 glacial area alone is expected to shrink by one-fifth, to 100,000 square
 kilometers.

 The disappearance of Earth's ice cover would significantly alter the 
global
 climate-though the net effects remain unknown. Ice, particularly polar 
ice,
 reflects large amounts of solar energy back into space, and helps keep the
 planet cool. When ice melts, however, this exposes land and water surfaces 
that
 retain heat-leading to even more melt and creating a feedback loop that
 accelerates the overall warming process. But excessive ice melt in the 
Arctic
 could also have a cooling effect in parts of Europe and the eastern United
 States, as the influx of fresh water into the North Atlantic may disrupt 
ocean
 circulation patterns that enable the warm Gulf Stream to flow north.

 As mountain glaciers shrink, large regions that rely on glacial runoff for 
water
 supply could experience severe shortages. The Quelccaya Ice Cap, the 
traditional
 water source for Lima, Peru, is now retreating by some 30 meters a year-up 
from
 only 3 meters a year before 1990-posing a threat to the city's 10 million
 residents. And in northern India, a region already facing severe water 
scarcity,
 an estimated 500 million people depend on the tributaries of the 
glacier-fed
 Indus and Ganges rivers for irrigation and drinking water. But as the 
Himalayas
 melt, these rivers are expected to initially swell and then fall to 
dangerously
 low levels, particularly in summer. (In 1999, the Indus reached record 
high
 levels because of glacial melt.)

 Rapid glacial melting can also cause serious flood damage, particularly in
 heavily populated regions such as the Himalayas. In Nepal, a glacial lake 
burst
 in 1985, sending a 15-meter wall of water rushing 90 kilometers down the
 mountains, drowning people and destroying houses. A second lake near the
 country's Imja Glacier has now grown to 50 hectares, and is predicted to 
burst
 within the next five years, with similar consequences.

 Large-scale ice melt would also raise sea levels and flood coastal areas,
 currently home to about half the world's people. Over the past century, 
melting
 in ice caps and mountain glaciers has contributed on average about 
one-fifth of
 the estimated 10-25 centimeter (4-10 inch) global sea level rise-with the 
rest
 caused by thermal expansion of the ocean as the Earth warmed. But ice 
melt's
 share in sea level rise is increasing, and will accelerate if the larger 
ice
 sheets crumble. Antarctica alone is home to 70 percent of the planet's 
fresh
 water, and collapse of the WAIS, an ice mass the size of Mexico, would 
raise sea
 levels by an estimated 6 meters-while melting of both Antarctic ice sheets 
would
 raise them nearly 70 meters. (Loss of the Arctic sea ice or of the 
floating
 Antarctic ice shelves would have no effect on sea level because these 
already
 displace water.)

 Wildlife is already suffering as a result of global ice melt-particularly 
at the
 poles, where marine mammals, seabirds, and other creatures depend on food 
found
 at the ice edge. In northern Canada, reports of hunger and weight loss 
among
 polar bears have been correlated with changes in the ice cover. And in
 Antarctica, loss of the sea ice, together with rising air temperatures and
 increased precipitation, is altering the habitats as well as feeding and
 breeding patterns of penguins and seals.


 TABLE 1:  SELECTED EXAMPLES OF ICE MELT AROUND THE WORLD



 Arctic Sea Ice
 Arctic Ocean
 Has shrunk by 6 percent since 1978, with a 14 percent loss of thicker,
 year-round ice. Has thinned by 40 percent in less than 30 years.

 Greenland Ice Sheet
 Greenland
 Has thinned by more than a meter a year on its southern and eastern edges 
since
 1993.

 Columbia Glacier
 Alaska, United States
 Has retreated nearly 13 kilometers since 1982. In 1999, retreat rate 
increased
 from 25 meters per day to 35 meters per day.

 Glacier National Park
 Rocky Mtns., United States
 Since 1850, the number of glaciers has dropped from 150 to fewer than 50.
 Remaining glaciers could disappear completely in 30 years.

 Antarctic Sea Ice
 Southern Ocean
 Ice to the west of the Antarctic Peninsula decreased by some 20 percent 
between
 1973 and 1993, and continues to decline.

 Pine Island Glacier
 West Antarctica
 Grounding line (where glacier hits ocean and floats) retreated 1.2 
kilometers a
 year between 1992 and 1996. Ice thinned at a rate of 3.5 meters per year.

 Larsen B Ice Shelf
 Antarctic Peninsula
 Calved a 200 km2 iceberg in early 1998. Lost an additional 1,714 km2 
during the
 1998-1999 season, and 300 km2 so far during the 1999-2000 season.

 Tasman Glacier
 New Zealand
 Terminus has retreated 3 kilometers since 1971, and main front has 
retreated 1.5
 kilometers since 1982. Has thinned by up to 200 meters on average since 
the
 1971-82 period. Icebergs began to break off in 1991, accelerating the 
collapse.

 Meren, Carstenz, and Northwall Firn Glaciers
 Irian Jaya, Indonesia
 Rate of retreat increased to 45 meters a year in 1995, up from only 30 
meters a
 year in 1936. Glacial area shrank by some 84 percent between 1936 and 
1995.
 Meren Glacier is now close to disappearing altogether.

 Dokriani Bamak Glacier
 Himalayas, India
 Retreated by 20 meters in 1998, compared with an average retreat of 16.5 
meters
 over the previous 5 years. Has retreated a total of 805 meters since 1990.

 Duosuogang Peak
 Ulan Ula Mtns., China
 Glaciers have shrunk by some 60 percent since the early 1970s.

 Tien Shan Mountains
 Central Asia
 Twenty-two percent of glacial ice volume has disappeared in the past 40 
years.

 Caucasus Mountains
 Russia
 Glacial volume has declined by 50 percent in the past century.

 Alps
 Western Europe
 Glacial area has shrunk by 35 to 40 percent and volume has declined by 
more than
 50 percent since 1850. Glaciers could be reduced to only a small fraction 
of
 their present mass within decades.

 Mt. Kenya
 Kenya
 Largest glacier has lost 92 percent of its mass since the late 1800s.

 Speka Glacier
 Uganda
 Retreated by more than 150 meters between 1977 and 1990, compared with 
only
 35-45 meters between 1958 and 1977.

 Upsala Glacier
 Argentina
 Has retreated 60 meters a year on average over the last 60 years, and rate 
is
 accelerating.

 Quelccaya Glacier
 Andes, Peru
 Rate of retreat increased to 30 meters a year in the 1990s, up from only 3
 meters a year between the 1970s and 1990.

 Sources available upon request. For additional examples go to
 http://www.worldwatch.org/alerts/000306t.html

 END


----------------------------------------------------------------------
Ocean Temperature Rise May Mean Warmer Times Ahead
By Curt Suplee
Washington Post Staff Writer
Friday, March 24, 2000; Page A07
The temperature of the world's oceans has increased dramatically over
the past four decades, according to a major study that adds new
credibility
to projections of increased global warming.
http://washingtonpost.com/wp-dyn/articles/A4512-2000Mar23.html

March 24, 2000


Researchers Find Ocean Temperature Rising, Even in the Depths
The New York Times
by WILLIAM K. STEVENS
An important piece of the global-warming picture has come into clearer
focus with a confirmation by scientists that the world's oceans have
soaked
up much of the warming of the last four decades, delaying its full effect
on
the atmosphere and thus on climate

http://www.nytimes.com/library/national/science/032400sci-environ-climate.ht
ml

Oceans have been getting warmer in last 50 years

http://sg.dailynews.yahoo.com/headlines/technology/afp/article.html?s=singap

ore/headlines/000324/technology/afp/Oceans_have_been_getting_warmer_in_last_
50_years.html



Sea Temperatures On The Rise
Oceans Of New Evidence Mount On Global Warming
http://cbsnews.cbs.com/now/story/0,1597,175578-412,00.shtml

WORLD OCEAN HAS WARMED SIGNIFICANTLY OVER PAST 40 YEARS
NOAA
March 23, 2000 - Scientists at NOAA have discovered that the world ocean
has
warmed significantly during the past 40 years. The largest warming has
occurred in the upper 300 meters of the world ocean on average by 0.56
degrees Fahrenheit. The water in the upper 3000 meters of the world ocean
warmed on average by 0.11 degrees Fahrenheit. These findings represent the
first time scientists have quantified temperature changes in all of the
world's oceans from the surface to 3000 meters depth
http://www.noaanews.noaa.gov/stories/s399.htm



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