"Greenhouse gases" (such as water vapour, methane and carbon dioxide) in the earth's atmosphere are released by natural processes on earth and are essential for life. They form an insulating layer around the planet which traps warmth from the sun and so prevents the earth from being frozen and lifeless. They are known as greenhouse gases because of this warming effect.
Human activities (such as industry and agriculture) influence global climate by releasing more greenhouse gases into the atmosphere than would occur there naturally as part of the earth's carbon cycle. The extra concentrations of these gases trap more of the sun's warmth by preventing it from escaping into space, so increasing global temperatures.
Higher average temperatures can have both helpful and unhelpful effects in relation to the greenhouse effect. These complex effects of global warming are studied as part of the worldwide climate research undertaken on behalf of the United Nations Intergovernmental Panel on Climate Change (IPCC).
