What is climate change?

Climate change is a large-scale, long-term shift in the planet's weather patterns or average temperatures. Earth has had tropical climates and ice ages many times in its 4.5 billion years. So what's happening now?

Since the last ice age, which ended about 11,000 years ago, Earth's climate has been relatively stable at about 14 °C. However, in recent years, the average temperature has been increasing.

The information below details the seven main sources of evidence for climate change. You can find out more about the difference between weather and climate, what drives our climate and how our climate is changing in our climate infographic or scroll to the foot of this page for our video - What is climate change?

Higher temperatures

Scientific research shows that the climate - that is, the average temperature of the planet's surface - has risen by 0.89 °C from 1901 to 2012. Compared with climate change patterns throughout Earth's history, the rate of temperature rise since the Industrial Revolution is extremely high.

Changing rainfall

There have been observed changes in precipitation, but not all areas have data over long periods. Rainfall has increased in the mid-latitudes of the northern hemisphere since the beginning of the 20th century. There are also changes between seasons in different regions. For example, the UK's summer rainfall is decreasing on average, while winter rainfall is increasing. There is also evidence that heavy rainfall events have become more intensive, especially over North America.

Changes in nature

Changes in the seasons (such as the UK spring starting earlier, autumn starting later) are bringing changes in the behaviour of species, for example, butterflies appearing earlier in the year and birds shifting their migration patterns.

Sea level rises

Since 1900, sea levels have risen by about 10 cm around the UK and about 19 cm globally, on average. The rate of sea-level rise has increased in recent decades.

Retreating glaciers

Glaciers all over the world - in the Alps, Rockies, Andes, Himalayas, Africa and Alaska - are melting and the rate of shrinkage has increased in recent decades.

Sea ice

Arctic sea-ice has been declining since the late 1970s, reducing by about 4%, or 0.6 million square kilometres (an area about the size of Madagascar) per decade. At the same time Antarctic sea-ice has increased, but at a slower rate of about 1.5% per decade.

Ice sheets

The Greenland and Antarctic ice sheets, which between them store the majority of the world's fresh water, are both shrinking at an accelerating rate.

Last updated: 3 February 2014

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What is climate change? - Met Office climate change guide
Earth's climate has changed many times in response to natural factors but over the course of the last century we have seen an unusual rise in the average global temperature that cannot be explained by natural causes alone

What is climate change? transcript What is climate change? transcript (PDF, 89 kB)