Climate change

Climate change means the variation in the earth global climate or in regional climates over time.

It describes changes in the state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the  earth  forces from outside (e.g. variations in sunlight intensity) or, more recently, human activities.

The climate of the Earth is always changing. In the past it has
altered as a result of natural causes. Nowadays, however, the term
climate change is generally used when referring to changes in our
climate which have been identified since the early part of the 1900's.
The changes we've seen over recent years and those which are predicted
over the next 80 years are thought to be mainly as a result of human
behaviour rather than due to natural changes in the atmosphere.

The greenhouse effect
is very important when we talk about climate change as it relates to
the gases which keep the Earth warm. It is the extra greenhouse gases
which humans have released which are thought to pose the strongest
threat.

There has been debate over the cause of rising global temperatures.
Some argued it was a natural fluctuation, whilst others that it was
caused by human activity. This debate is now over.

In February 2007, an international panel of experts (the Inter-Governmental Panel on Climate Change) concluded:

• Global warming is occurring.
• Increase in global temperature is a result of human activities.
• Given
  current trends, temperature extremes, heat waves, and heavy rains will
  continue to escalate in frequency. The earth’s temperature and seas
  will continue to rise into the next millennium.

These
climate change effects are due to an increase in greenhouse gases in
the atmosphere. The main gases are carbon dioxide, methane, nitrous
oxide and fluorocarbons, principally from the burning of fossil fuels,
forest destruction and agriculture (rice field cultivation and the
keeping of livestock). Water vapour in the atmosphere also plays a
role.

The scientific community often talk about global
warming potential. This relates to the warming effect of a greenhouse
gas in relation to the measured effect for carbon dioxide.

This
web site, and most other sources of information on global warming,
looks only at carbon dioxide. It is the major greenhouse gas produced
by humans, which is having the single greatest effect on climate
change.

The graph below shows the link between increasing levels of carbon dioxide in the atmosphere and global temperature change.

The increase in carbon dioxide is largely due to the burning of fossil fuels (coal, oil and gas) over the last two centuries.