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Natural/ physical causes for climate change LO: to explain the natural cause of long term climate fluctuations Industrialisation Homo Sapiens Orbital geometry Milankovitch cycles https://www.youtube.com/watch?v=TWJyeyV92W4 • Earth's climate undergoes 120,000 year cycles of ice ages broken by short warm periods called interglacials. • The cycle is driven by Milankovitch cycles. Long term changes in the Earth's orbit trigger an initial warming which warms the oceans and melts ice sheets - this releases CO2. • The extra CO2 in the atmosphere causes further warming leading to interglacials ending the ice ages. • For the past 12,000 years, we've been in an interglacial. • The current trend of the Milankovitch cycle is a gradual cooling down towards an ice age. Changes in solar output • Caption for Image Four: The Sun shows signs of variability, such as its eleven-year sunspot cycle. In that time, it goes from a minimum (seen here in 1996) to a maximum (2000) period of activity that affects us everyday. When particularly active, solar storms can spew tons of radiation to Earth in the form of Coronal Mass Ejections (CMEs) that can affect power grids, spacecraft, and communication systems. SUPER: NASA / ESA Catastrophic events-e.g. volcanic eruptions https://www.y outube.com/ watch?v=Pd EWUoSOJ7 M Volcanoes • • • • • • Volcanic eruptions spew sulphate aerosols into the atmosphere which has a cooling effect on global temperatures. These aerosols reflect incoming sunlight, causing a 'global dimming' effect. Usually, the cooling effect lasts several years until the aerosols are washed out of the atmosphere. In the case of large eruptions or a succession of eruptions such as in the early 1800's, the cooling effect can last several decades. Strong volcanic activity exacerbated the Little Ice Age in the 1800's. Observational and modelling studies (e.g. Kelly & Sear, 1984; Sear et al., 1987) of the likely effect of recent volcanic eruptions suggest that an individual eruption may cause a global cooling of up to 0.3°C, with the effects lasting 1 to 2 years. Such a cooling event has been observed in the global temperature record in the aftermath of the eruption of Mount Pinatubo in June 1991. The climate forcing associated with individual eruptions is, however, relatively short-lived compared to the time needed to influence the heat storage of the oceans (Henderson-Sellers & Robinson, 1986). The temperature anomaly due to a single volcanic event is thus unlikely to persist or lead, through feedback effects, to significant long-term climatic changes. How do each of these factors cause climate change? Sample question Mark scheme