the effects be of a massive rise in sea level? The vast majority of the world's great cities are on the coast,
including virtually every city with a population of above 10 million. They
were built there to utilise the sea by fishing and trading abroad. Many grew
because of the size of their harbours.
However, there are disadvantages to being located on the coast. It leaves
these cities extremely vulnerable to a rise in sea levels. A rise of just
a metre could mean that the ocean flowed into city streets at high tide.
A rise of several metres would make holding this water back near impossible
without hugely expensive flood defences. A rise of much more than that could
mean that low lying area of cities would have to be evacuated. Imagine the
consequences of what would happen if sea levels were to rise by more than
New York, Los Angeles, Rio de Janeiro, Sau Paulo, Bombay, Tokyo, Kobe, London
and Shanghai, to name but a few, would all be swamped by this rise. Not only
cities would suffer: thousands of islands would disappear, which would be
especially difficult to evacuate in poor countries. Much of the world's best
farmland is below this height and the loss of it could mean massive food
shortages around the world. Our already overcrowded world would then have
even less space and less food to go around.
What might cause sea levels to rise? Global warming could potentially cause this massive increase. Global
warming is a proven fact, no scientist debates that temperatures are rising.
The debate is whether this is caused by greenhouse gasses (like carbon dioxide,
methane and CFCs), but this is irrelevant to the ice caps.
Global warming is having a dual effect on sea levels. Rising global temperatures
make the sea warmer. As liquids warm they expand. This means that without
any more water entering the sea, it is getting deeper. Scientists are already
beginning to observe this effect as sea levels start to rise, watched in
horror by inhabitants of small islands as the coastline recedes.
The second effect is that the increased temperature will make Antarctica
start to melt. As the ice warms, it melts, putting more water into the sea.
If all of Antarctica melts sea levels would rise by 55 metres, although it
would take a very large temperature rise for this to happen.
Is there evidence that the ice caps are melting? Clearly it is vital to research if the ice caps are melting. A
large amount of separate research suggests that it is already happening,
and the rate of this can only increase if the predicted rise in the rate
of global warming occurs. Here is only a small part of the evidence:
· Since the 1950s the Arctic ice sheet has become 40% thinner during
the summer and covers 15% less area.
· Arctic temperatures are the warmest for 400 years
· Since the 1960s snow cover has declined by 10%
· In just seven years, Pine Island Glacier, part of the Antarctic
ice sheet, has thinned by more than 5 feet.
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