Why is climate change happening?

There is consensus among the international community that human (anthropogenic) activities are the main cause of the recent global warming.

In its latest AR4 Synthesis Report, the UN Intergovernmental Panel on Climate Change (IPCC) concludes that:-

Most of the observed increase in globally-averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (man-made) global greenhouse gas (GHG) concentrations.

According to the IPCC:-

• GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004.
• Global atmospheric concentrations of CO2, methane (CH4) and nitrous oxide (N2O) have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years.
• Atmospheric concentrations of CO2 (379ppm) and methane (1774 ppb) in 2005 exceed by far the natural range over the last 650,000 years.
• Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution.
• There is high agreement and much evidence that with current climate change mitigation policies and related sustainable development practices, global GHG emissions will continue to grow over the next few decades.

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.