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What is climate?
Ever since the human race began to walk the earth, we
have been dominated by the climate. Our tribal ancestors were
constantly
on the
move, following large mammals on their
migratory routes and trying to avoid the extremes of cold, rain,
and heat. But
in
due course
they settled, and learned to adapt
to the climatic surroundings that
ruled
them.
Today, whoever and wherever we are, the climate still
dictates the way we live. The cities we build, the clothes we
wear, the kind of homes we live in, the food we eat, even our
temperament... all are based on the weather.
Climate is the long-term characteristic weather
pattern
of any region in the world. And if climate controls us, it in
turn is regulated by
a myriad of factors - not least the
radiation and angle of the sun, the rotation of the earth, the
composition of air masses, the proximity and size of the oceans,
the
height of the mountains, and the
depth of the valleys.
What is climate
change?
Climate change is a
warming or a
cooling of the
weather.
Over the 4.5 billion years that the earth has existed, we have
swung between both. Ice ages have come and gone, and have
lasted
for up to 100,000 years.
They have been followed by shorter, warmer periods, one
of which we are in at the moment: the earth's average
temperature is around 4ºC hotter than it was during the last
ice age some 13,000 years ago.
But recently, things have accelerated so much that it is now
also half a degree warmer than it was during the 1860s. That may
not seem a very big increase at all, but it is
huge
for a
relatively short
timespan
of 130 years.
And there is one significant difference between
previous periods of warmth and the current one. In the past,
they have been due to natural phenomena and have taken thousands
of years
to
evolve, so species have had time to adapt. But this
time the cause is the 5.8 billion human beings in the world.
Data from ice
cores
suggest that we are living in the warmest
century for 600 years - and we certainly know that the final two
decades of the 20th century are the hottest on record. We are
turning up the planet's thermostat so fast that nature
can no
longer
cope.
What are
the causes?
Every time we turn on a
light switch, use a computer, watch TV, or cook a meal, the
chances are we are creating carbon dioxide (CO2), which is not
only the world's most abundant naturally occurring gas with the
potential to pollute, but also the principal contributor to
global warming.
The electricity we use is generated by power stations,
the vast majority of which burn "fossil fuels" - so
called because they have been created over millions of years by
the slow subterranean
decay
of vegetation and other living
matter. The three fossil fuels we burn are coal, oil, and
natural gas, each of which has hydrogen and carbon in its
make-up. When
they are
burned, these components mix with oxygen
in the atmosphere. The result is CO2.
We have been
pumping
CO2 into the air since the
Industrial Revolution 200 years ago, and now we are paying the
price. Carbon dioxide and other gases, including methane and
nitrous oxide (generated by activities such as rubbish disposal,
cattle farming, and the use of fertilizers), and highly damaging
chlorofluorocarbons (CFCs), have now formed a blanket around the
earth. As each year
goes
by, these gases
trap
more and more heat
that would otherwise escape into space. The heat
rebounds
onto
the earth's surface, and the planet's temperature rises -
creating what is commonly called the "greenhouse
effect".
At the speed our climate is changing, the world will
soon be warmer than at any time in the last 10,000 years.
Almost 5 billion tons of CO2 are produced each year
by people in the prosperous developed world. And we add to the
problem every time we drive a car, take a flight, or even burn
wood.
Trees are great natural
storehouses
of CO2, some
retaining it for a century or more. Over the years, billions of
tonnes of CO2 in the atmosphere are absorbed by the world's
forests which, in so doing, help stabilize the world's climate.
But when speculators and developers
set forests alight
- as they
do frequently when clearing land for agriculture or for town
expansion - the gas retained over a lifetime is released back
into the air. The ecological damage is compounded by the fact
that, because the forests are not replaced, there are fewer
trees to absorb CO2, when more are needed than ever before. |
