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Impacts
of Global Warming
The
rate of global warming and sea level rise during the this century could be devastating. Estimated land losses range from 0.05%
for Uruguay to about 80% for the Majuro Atoll in the Marshall Islands.
Map
from Worldatlas.com
A 1M
(3 feet) sea-level rise would affect 6 million people in Egypt, with 12% to
15% of agricultural land lost, 13 million in Bangladesh, with 16% of
national rice production lost, and 72 million in China and "tens of
thousands" of hectares(1 hectare =2.47 acres) of agricultural land.
Small, low-lying island states
and countries with big coastal populations such as the Marshall Islands and
Bangladesh could see catastrophic damage from the rise.
Global
warming is at the root of the increase as the Earth’s
climbing temperatures melt the Arctic sea ice and Antarctica.
Bangladesh
Population 129,000,000
CIA
Map
Map
from Worldatlas.com
Ice sheets and Glaciers Melting
Around
the world, ice sheets and glaciers are melting at a rate unprecedented
since record-keeping began. Changes in the area and volume of the two
polar ice sheets in Antarctica and Greenland are intricately linked
to changes in global climate and could result in sea-level changes that
would severely affect the densely populated coastal regions on Earth.
In
Antarctica the West Antarctic ice sheet is currently shrinking
substantially, and has been for the last decade.
In
Greenland the ice sheet that is shrinking dramatically at the edges and
growing at its higher interior elevations, such that there is a net loss
of ice that is far greater than it was in the last decade.Greenland's
massive ice sheet has lost nearly 100 gigatons of ice annually recently,
much of it in low-elevation regions along the continent's southeastern
coast.
Greenland
Credit:NASA
These
losses are a result of increased melting, and faster flow at the edges, as
the floating ice that surrounds parts of Greenland and buttresses some of
the outlet glaciers melts.
Greenland's
low coastal regions lost 155 gigatons (41 cubic miles) of ice per year
between 2003 and 2005 from excess melting and icebergs, while the
high-elevation interior gained 54 gigatons (14 cubic miles) annually from
excess snowfall.
NASA
satellite data has revealed regional changes in the weight of the
Greenland ice sheet between 2003 and 2005. Low coastal regions (blue) lost
three times as much ice per year from excess melting and icebergs than the
high-elevation interior (orange/red) gained from excess snowfall.
NASA data shows that Arctic perennial sea ice, which normally
survives the summer melt season and remains year-round, shrunk abruptly by 14
percent between 2004 and 2005. According to researchers, the loss of perennial
ice in the East Arctic Ocean neared 50 percent during that time as some of the
ice moved from the East Arctic to the West. The overall decrease in winter Arctic perennial sea ice totals 280,000 square
miles--an area the size of Texas. Perennial ice can be 10 or more feet thick. It
was replaced by new, seasonal ice only about one to seven feet thick that is
more vulnerable to summer melt.
According
to the National Snow and Ice Data Center, the Northern Hemisphere sea ice
extent, which is measured from passive microwave instruments onboard NOAA
satellites, was 5.9 million square kilometers as of September 14, 2006, the
second lowest on record (image to the left). This is the fifth consecutive year
September sea ice extent has been below the long-term (1978-2000) mean. The
September rate of sea ice decline is now almost 9 percent per decade (60,421
square kilometers per year).
Greenland
contains about 9 percent of all ice on Earth—also enough water to raise
sea level by 5 meters. Should either West Antarctica or Greenland
surrender its ice sheet to the ocean, much of the southern half of Florida
would be under water.
Woods
Hole Oceanographic
Change
in coastlines due to a 6-m rise in sea level. Red denotes present land
areas that will be under water. Eastern US (top) and South Asia (bottom).
Credit
Images courtesy of Tad Pfeffer, Institute of Arctic and Alpine Research,
University of Colorado
The
total surface area of glaciers worldwide has decreased by 50% since the end of
the 19th century . Currently glacier retreat rates and mass balance losses have
been increasing in the Andes, Alps, Himalaya's, Rocky Mountains and North
Cascades. The snow cap that has covered the top of Mount Kilimanjaro for the
past 11,000 years since the last ice age has almost disappeared.
The
loss of glaciers not only directly causes landslides, flash floods and glacial
lake overflow, but also increases annual variation in water flows in rivers.
Glacier runoff declines in the summer as glaciers decrease in size, this decline
is already observable in several regions . Glaciers retain water on mountains in
high precipitation years, since the snow cover accumulating on glaciers protects
the ice from melting. In warmer and drier years, glaciers offset the lower
precipitation amounts with a higher meltwater input .
In
1978, the Qori Kalis Glacier looked like this, flowing out from the
Quelccaya Ice Cap in the Peruvian Andes Mountains
In
2000, the view of Qori Kalis has changed dramatically with a massive
10-acre lake forming at the ice margin
Mt.
Kilimanjaro’s Receding Glaciers
Space
Shuttle Photograph
Permafrost
Global
warming may accelerate as rising temperatures in the Arctic
melt the permafrost causing it to release greenhouse gases into the
atmosphere . An estimated 14 per cent of the
world's carbon is stored in Arctic lands. This could accelerate the
"greenhouse effect".
Global
Warming And The Gulf Stream
Wind
and the rotation of the Earth are important in determining the flow of
surface currents and local areas of upwelling and downwelling, but the
true driving force of deep water movement is thermohaline circulation.
Sometimes called the ocean conveyer belt, this mechanism is responsible
for bringing the oxygen that sustains life to the deepest reaches of the
sea, and in moving warmer waters from the tropics towards the poles.
Movement of this conveyer belt depends on sinking of cold water in
certain polar regions, thereby triggering the global thermohaline
circulation.
THE
ARCTIC HALOCLIINE—When sea ice forms, it releases salt into surface waters.
These waters become denser and sink to form the Arctic halocline—a layer of
cold water that acts as barrier between sea ice and deeper warmer water that
could melt the ice. (Illustration by Jayne Doucette, WHOI)
The
Gulf Stream merges into the North Atlantic Current. This warm water then
flows up the Norwegian coast, with a westward branch warming Greenland's
tip, at 60°NIt keeps northern Europe about nine to eighteen degrees
warmer in the winter than comparable latitudes elsewhere.
Global warming
could alter this. Because freshwater is less dense than seawater,
increased precipitation, melting of polar glaciers and ice caps could
block the system by reducing the amount of cold water that sinks
downwards.
As
water travels through the water cycle, some water will become part of
The Global Conveyer Belt and can take up to 1,000 years to complete this
global circuit. It represents in a simple way how ocean currents carry
warm surface waters from the equator toward the poles and moderate
global climate. NASA Graphic
In
the Atlantic, warm, high-salinity water flows northward in the Gulf
Stream along the east coast of North America. Some of this water
continues northeastward in the North Atlantic Current toward Iceland and
Norway. Off the coast of Greenland, a portion of the surface water
cools, becomes dense, and sinks. A further portion of surface water
continues into the Arctic Ocean before also cooling and sinking.
Together these sinking plumes off Greenland and in the Arctic form
"deep water" that plays an important role in global oceanic
circulation.
Climate and
Health
Climate can have a profound
influence on human health both directly and indirectly. Some direct
effects include deaths and illnesses related to excessive heat or cold exposure.
Indirect effects of climate on health may involve respiratory disorders due to
air pollution, including spores and pollens. Incidences of waterborne
diseases, such as cholera, as well as food productivity and its relation to
nutrition are other indirect effects of climate on health.
Human health is also indirectly
affected by climate due to its influence on the abundance and geographic
distribution of disease vectors, such as mosquitoes and rodents. Several
studies suggest projected climate changes may result in expanded geographic
ranges for many mosquito-borne diseases.
Mosquitoes
can transmit many viruses, over 100 of which are known to infect humans.
These include malaria, dengue fever, yellow fever, and severe and sometimes
fatal encephalitis and haemorrhagic fever.
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