Climate change

What is climate change?

Climate refers to the average weather experienced over a long period. This includes temperature, wind and rainfall patterns. The climate of the Earth is not static, and has changed many times in response to a variety of natural causes.

The Earth has warmed by nearly 1°C over the last hundred years and around half of this warming has occurred since the 1970s. The 20th century was probably the warmest century in the last 1,000 years. The 1990s were the warmest decade in the last 100 years.

The changes in global climate are due to a combination of both natural and human causes.

The main human influence on global climate is emissions of the key greenhouse gases, these are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The accumulation of these gases in the atmosphere strengthens the greenhouse effect.

Billions of tonnes of CO2 are emitted globally each year through fossil fuel use and further emissions caused by land use change, largely by deforestation. The concentrations of these gases in the atmosphere have now reached levels unprecedented for tens of thousands of years.

Climate experts predict that average global temperatures are likely to rise between 1 and 6°C above 1990 levels by the end of this century, depending upon the rate of emissions.

This increase will result in a further rise in global sea levels of between 20 and 60cm by the end of this century, from continued melting of ice caps, glaciers and sea ice, changes in rainfall patterns and intensification of tropical cyclones.

For the UK, climate change means hotter, drier summers, milder wetter winters, higher sea levels and an increased flood risk to coastal areas. Also heavy rainfall events will become more frequent with increased likelihood of storms.

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The climate of the Earth is not static, and has changed many times in response to a variety of natural causes.