It is now universally recognised that human-induced climate change could have major adverse consequences for the world’s ecosystems and societies. Climate change is caused by the emission of greenhouse gases, which trap long-wave radiation in the upper atmosphere and consequently raise atmospheric temperatures. This also produces other changes in the climate system. Carbon dioxide is the most important of these gases and its atmospheric concentration has increased exponentially since the beginning of the industrial revolution as a result of fossil fuel combustion and land-use change. In 1800, the atmospheric concentration of carbon dioxide was about 280 parts per million; today it is about 350 ppm and rising. Similar increases have been observed for other greenhouse gases such as methane and nitrous oxide.