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The threat of catastrophic climate
change resulting from greenhouse gas emissions is no
longer in doubt at either a scientific or a political
level. Against pre-industrial carbon dioxide levels of
280ppm, current levels are 389ppm and rising faster than
ever, with a tipping point expected at 450ppm, after
which climate may be irreversible.
The atmosphere of the earth is made
up of a number of gases: roughly 78% nitrogen, 21% oxygen,
and 1% argon, along with water vapour which varies according
to the weather conditions. Carbon dioxide makes up only
about 0.039% of the atmosphere but it and other greenhouse
gases including methane and nitrous oxide and ozone have
the power to alter the climate because they can trap
the heat that comes from the sun within the atmosphere.
The amount of greenhouse gases in the
atmosphere is determined by the balance between what
is emitted and what is absorbed in carbon sinks. When
living plants grow they photosynthesis and absorb carbon
dioxide and give off oxygen. The carbon is held above
ground in the living vegetation and below ground in the
soil in the roots and humus. Animals that eat the plants
absorb carbon into their bodies and release carbon dioxide
into the air when they breathe. Finally, when plants
and animals die and decompose, they release more carbon
dioxide back into the air. The oceans also act as sinks;
they can both absorb and release carbon dioxide.
CO₂ levels increasing
As a result of human activities, carbon dioxide concentrations
in the atmosphere have increased by 25% over the past
200 years. Before the industrial revolution they were
at 280 parts per million. The rate of increase is rising.
From 1970 to 2000, the concentration rose by about
1.5ppm each year, but since 2000 it has risen to an
average 2.1ppm.
The effects everywhere are apparent.
Glaciers are melting at an unprecedented rate; there
has been a thinning of the icecaps in the Arctic and
recently the Antarctic. According to the Intergovernmental
Panel on Climate Change, the rise in global temperature
is expected to reach 3-4 degrees by the end of this century.
While this rise may seem small, it can have dramatic
and devastating impacts. Rising sea levels have already
engulfed two uninhabited Pacific islands and now threaten
inhabited islands in the same area. Coastal cities, including
major capitals around the world could be engulfed.
Rising temperatures are also expected
to bring an increase in severe weather occurrences, drought,
devastating storms and flooding which can hit agriculture,
potentially leading to famine and wars for scarce resources.
Rising temperatures could mean that tropical diseases
start appearing in areas which so far have been unaffected.
Need to act now
Lord Stern, the World Bank’s former chief economist warned
back in 2006 that countries needed to spend 1% of their
GDP to stop greenhouse gases rising to dangerous levels.
Failure to do this, the report warned would lead to
damage costing much more - at least 5% and perhaps
more than 20% of global GDP.
Now in a new book, he has concluded
that the science he based his predictions on is out of
date. He forecast that temperatures are likely to rise
by at least two degrees Celsius by the end of the century.
He warned that if nothing is done to keep emissions low
temperatures might rise by up to six degrees with catastrophic
consequences.
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