What is the evidence for climate change?

There is now consensus among the international community that the world is warming and that this is mainly the result of human activities.

The UN Intergovernmental Panel on Climate Change (IPCC), a body that was set up by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), has been reviewing worldwide research on climate change since 1988. In its latest AR4 Synthesis Report for the IPCC meeting in Valencia in November 2007, it concluded that:-

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.

According to the IPCC:-

• Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850).
• Global average sea level has risen since 1961 at an average rate of 1.8 mm/year and since 1993 at 3.1 mm/year.
• Satellite data since 1978 show that annual average Arctic sea ice extent has shrunk by 2.7% per decade. Mountain glaciers and snow cover on average have declined in both hemispheres.
• From 1900 to 2005, precipitation increased significantly in eastern parts of North and South America, northern Europe and northern and central Asia but declined in the Sahel, the Mediterranean, southern Africa and parts of southern Asia.

Resources

1. Powerpoint presentation on the evidence, reasons and implications of climate change

2. IPCC presentations are available for download on the IPCC website

3. Resources for understanding and communicating climate change to the general public are available on the Climate Challenge website.

4. DEFRA's Climate Change and Energy web pages have lots more useful information and links.