Page 93 - (DK) Ocean - The Definitive Visual Guide

Global Warming 91

and Sea-level Rise

The measurement of global sea-level change is
EFFECTS OF GLOBAL WARMING
complex and, until satellite-based techniques were
introduced in 1992, was somewhat imprecise. During
the 1980s, a consensus emerged that sea level had
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been rising at / 32– / 8 in (1–3 mm) per year since
1900, whereas the new satellite techniques indicate
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a current average rise of / 8 in (3 mm) per year. Since
1900, there has also been a rise in the temperature of
Earth’s atmosphere and oceans (global warming) of
about 1.44˚F (0.8˚C). There are two plausible
mechanisms by which the temperature rise might be
linked to the sea-level rise: first, through melting of
glaciers and ice sheets, which increases the amount of
water in the oceans; and second, through the GLACIER RETREAT PERUVIAN ANDES Global warming is having a marked impact
on the world’s glaciers. The majority have shrunk since 1975,
expansion of seawater as it warms. Since there are no as their ice has melted faster than new ice has formed. These
other convincing explanations of what might be photographs from the same viewpoint show the extent of a glacier
in the Cordillera Blanca, Peru, in 1980 (left) and 2002 (right).
causing the sea-level rise, the view of most scientists
is that global warming is the cause.
FUNAFUTI ATOLL This atoll is
Based on different models of the future course of part of Tuvalu, a group of small,
low-lying Pacific islands whose
global warming (which most scientists now believe is
future existence is threatened
linked to human activity), it is possible to make various by sea-level rise.
predictions of how sea level will change in the future.
For example, the Intergovernmental Panel on Climate
Change predicts that, by the end of the 21st century,
there will be a further sea-level rise of 11–38 / 2 in
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(0.28–0.98 mm). This rise will displace tens of millions SUBMERGING ISLANDS HIGH TIDE Homes on
of people living in low-lying coastal areas and have Funafuti Atoll are already
flooded by lagoon waters
a devastating effect on some small island nations. from time to time during
Continued global warming will eventually melt the exceptionally high tides.
Greenland Ice Sheet, raising sea levels by about 23 ft
(7 m), flooding most of the world’s coastal cities.

Sea-level Rise in Southeastern US
The maps below indicate the areas of the southeastern US that
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would be threatened by sea-level rises of 3/4 ft (1 m), 6/2 ft (2 m),
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and 20 ft (6 m). A 3/4-ft (1-m) rise is a little above the upper end
of estimates for what can be expected this century. With this rise,
parts of Florida and southern Louisiana would be inundated up
to 18 miles (30 km) from the present coastline. A rise of 20 ft
(6 m) — which would be exceeded if the Greenland Ice Sheet
were to melt completely — would submerge a large part of
Florida, while Louisiana would
be flooded as much as 50 miles
ATLANTIC OCEAN to be highly unlikely in this Greenland Ice Sheet. A rise of 2 ft (65 cm) would cause loss of 40
Jacksonville (80 km) in from the present POPULATIONS AT RISK CITY UNDER WATER Dhaka, the capital of Bangladesh, and about
three-quarters of the country’s land area, is less than 27 ft (8 m) above
Georgetown coastline. This would appear sea level. Much of the country would be flooded by melting of the
century but could happen
Galveston New Orleans within a few hundred years percent of productive land in southern Bangladesh. About 20 million
people in coastal areas are affected by salinity in drinking water now.
if global warming continues.
Miami
Gulf of Mexico
flooded area
STARVED TO DEATH
3 1 /4-ft (1-m) rise
Polar bears are one of OCEAN ENVIRONMENTS
the animal species most
ATLANTIC OCEAN ATLANTIC OCEAN use Arctic sea ice as their
Jacksonville Jacksonville severely threatened by
Georgetown Georgetown global warming. The bears
summer hunting ground,
Galveston New Orleans Galveston New Orleans ANIMALS IN DANGER and as the extent of sea ice
diminishes, so do their
Miami Miami
Gulf of Mexico Gulf of Mexico opportunities for hunting
6 1 /2-ft (2-m) rise 20-ft (6-m) rise and feeding.