What is Climate Change?
The term climate change is generally applied to changes in our
climate which have been identified since the early 1900s. The
changes seen in recent years and predicted over the next 80 or so
years are thought to be mainly the result of human behaviour rather
than natural changes. Globally, nine of the ten hottest years on
record have been during 1990 - 2002, with 1998 being the warmest
year since global records began in 1860. Borehole measurements
worldwide suggest a global surface warming of around 1'C during the
last 500 years - with about half of this warming occurring in the
20th Century. In the UK, winters have become wetter and summers
drier, and recent decades have seen an increase in the proportion
of winter rainfall in intense storms. This global warming is also
leading to rising sea levels, due largely to the melting of ice
sheets and mountain glaciers.
The greenhouse effect is an important mechanism of climate change,
and refers to the increased release (from human activity) and
accumulation in the upper atmosphere of greenhouse gases which
restrict the loss of heat from the earth and cause it to warm
up.
The most important greenhouse gases are carbon dioxide, methane and
nitrous oxide.
Average global temperatures now stand at 0.6'C above pre-industrial
levels - and atmospheric concentrations of carbon dioxide have
reached 379ppm, well up on pre-industrial levels of 280ppm.