ABSTRACT

Climate has varied from times known loosely as 'ice ages' or 'glacial periods', when huge ice sheets covered large areas that are now ice-free, to periods like now when ice sheets are largely confined to Antarctica, Greenland and the floating Arctic sea ice. By studying many different proxy data records from places around the globe scientists have found evidence of global-scale climate changes. There are many contributory causes of past climate change, including continental drift, variations in the Earth's orbit around the Sun, changes in solar output, volcanic emissions, cosmic collisions and particulate matter in the atmosphere, commonly referred to as 'aerosols'. Climate change has occurred naturally in the past due to internal fluctuations in the climate system consisting of the atmosphere, the hydrosphere, and the cryosphere. Climate models have been run with various types of forcing including changes in greenhouse gases, volcanic particles, ozone, solar variations and the effects of air pollution particles.