Description: The current Holocene epoch is considered to be a time period of relatively stable climate compared to earlier geological periods. Still, some significant changes in temperature and sea level did occur. These climatic fluctuations include the Medieval Warm Period and the Little Ice Age, and more recently global warming. Temperature data for the 20th century shows a strong warming from about 1970 to the present day, typically associated with anthropogenic forcing including greenhouse gas and aerosol emissions. Volcanic eruptions also caused slight variations in the climate during the 20th century (e.g. Pinatubo in 1991). Aerosols released during a volcanic eruption are quickly distributed around the globe and act to increase the atmospheric albedo and block solar radiation. Therefore volcanic eruption signatures in climate data appear as short term decreases in temperature. General circulation models have been used to simulate the climate of the 20th century using both natural and anthropogenic climate forcings. These models indicate that anthropogenic forcings are likely responsible for the most recent rise in temperature.