What is Climate Change?

Climate Change is the change in climate over a time period that ranges from decades to centuries. The term refers to both natural and human-induced changes. The term “climate variability” refers to shorter term (years to decades) fluctuations in climate such as those caused by El Niño/Southern Oscillation.

The United Nations Framework Convention on Climate Change defines climate change as: “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”. In other words, the FCCC uses the term Climate Change to mean only those changes that are brought about by human activities.

Factors Affecting Global Climate There are many factors, both natural and of human origin, that determine the climate of the Earth.

Greenhouse Gases A number of minor gases in the atmosphere, although relatively transparent to sunlight, absorb most of the infrared heat energy transmitted by the Earth towards space. This phenomenon has been called the “greenhouse effect” and the absorbing gases that cause it “greenhouse gases”. Important greenhouse gases include: water vapour, carbon dioxide, methane, nitrous oxide, ozone, and halocarbons.

Climate Trends An analysis of temperature records shows that the Earth has warmed an average of 0.5°C over the past 100 years. The warming is real and significant though its intensity has varied from decade to decade, from region to region and from season to season.

Modelling the Global Climate One of the most effective ways of estimating our future climate is to use powerful computer simulations of past and present climates.

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