Climate Science
A joint statement in June 2005 (Global response to climate change) by the science academies of the G8 nations and of China, India and Brazil, stresses that the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action. This followed an earlier joint statement in 2001 by 16 National Academies of Science (The science of climate change) that recognised the Intergovernmental Panel on Climate Change (IPCC), which represents a consensus of the international scientific community, as the global authority on climate change science and its causes.
An increase in the atmospheric concentration of greenhouse gases from human activities such as burning fossil fuels, leads to an enhanced greenhouse effect. Greenhouse gases present in the atmosphere absorb outgoing infrared radiation from the earth surface (terrestrial radiation) causing some heat to be retained. This greenhouse property of the atmosphere acts as a natural blanket over the earths surface making it warmer than it would otherwise be. Without this effect the earths surface would be 20 to 30°C colder and much less suitable for life. However, changing the greenhouse properties of the atmosphere will lead to changes in the earths radiative energy budget (the balance between incoming energy from the Sun and outgoing energy from the Earth), which leads to a global warming and as a consequence will affect other aspects of the Earths climate.
International agreements aim to address the human induced changes of a so-called basket of 6 greenhouse gases, carbon dioxide; methane; nitrous oxide; hydrofluorocarbons (HFCs); perfluorocarbons (PFCs); and sulphur hexafluoride. Water vapour and ozone are also potent greenhouse gases.