London scoping - ukcip

Final Report
5
2. What is Climate Change?
2.1 Climate Change – An Introduction
The earth’s climate has been changing throughout its history and, until now, this has been
mostly due to natural causes.
The atmosphere maintains the earth’s temperature range by trapping a certain amount of the
incoming energy from the Sun. The amount of energy that is trapped depends on the proportion
of different gases in the atmosphere, which in turn determines the earth’s temperature. A
particular mixture of gases maintains the temperature within the range that supports life.
Changes in the proportion of gases can alter the earth’s temperature and hence weather patterns
which are also influenced by the earth’s geography (oceans, mountains, land masses etc). Thus
the atmosphere needs a certain proportion of greenhouse gases (called the greenhouse gas
concentration) in order to maintain an acceptable temperature range and hence support life.
There are concerns that because human activities have led to an increase in the levels of
greenhouse gases in the atmosphere, the climate is changing beyond its natural variability.
Climate change studies try to understand these changes and how they could affect us. This is
done by looking at historical meteorological measurements, such as temperature and rainfall,
and looking for changes beyond what can be considered natural. Computer based models are
then run that try to describe the behaviour of global weather system due to increases in
greenhouse gas levels. This is a complex task, as no model can hope to fully describe what is
happening or could possibly happen with the weather. However the models are improving and
are beginning to be able to more accurately describe what has been recorded historically and
thus scientists are becoming more confident that such models are able to predict future changes.
These models produce a range of possible events or scenarios, as there is no exact answer to
what may happen with the climate. They produce estimates of future climate such as rainfall
and temperature. This information can then be used to estimate what the impacts of climate
change could be such as the effect on water resources and flooding. Less rainfall could reduce
water resources. This in turn could affect agriculture, industry and domestic supplies. More
rainfall could increase flooding, leading to damage to buildings and land. Changes in
temperature could lead to changes in agriculture with different types of crops being grown and
changes in the length of the growing and harvesting season. Many animal and plant species are
sensitive to climatic factors, so changes in temperature and rainfall could also affect flora and
fauna.
So, the scenarios can be used to help plan future programmes that may be affected by climate
change such as where people live, the need for flood defence and water storage. However,
climate change is not the only change that is happening. There are other changes brought about
by social and economic trends. In some cases climate change may have only a minor impact
and in others it may be more significant. In some cases climate changes may be beneficial and
in other it may be adverse. Therefore consideration of possible future climate changes should
be undertaken as part of the consideration of the wide range of issues that may affect
organisations and people in the future.