The climate is made up of many dynamic physical, chemical and biochemical systems which influence the conditions on earth. These systems influence the atmosphere, the ocean, land surfaces and the cryosphere (iced areas such as the poles and glaciers). The climate is not the same as the weather. The weather is what happens on a day-to-day basis and the climate is the average of the weather over a long period of time. The weather changes – and so does the climate. Human activities that emit greenhouse gases into the atmosphere, such as burning fossil fuels and deforestation, are having an impact on the climate system. Anthropogenic climate change (that is, caused by humans) has come to be widely regarded as a major threat to human welfare and the ecological systems which humans and the planet depend upon – Professor Andrew Dobson and Karen Dickinson