The document discusses several natural causes of past climate change: 1) Solar activity, with periods of lower sunspot activity corresponding to "Little Ice Ages" and higher activity to warm periods like the Medieval Warm Period. However, solar activity does not correlate with warming since 1975. 2) Orbital cycles known as Milankovitch cycles, which cause ice ages and warm interglacial periods over 100,000 year cycles. 3) Large volcanic eruptions, which eject aerosols that reflect sunlight and cause short-term global cooling lasting several years. 4) Ocean circulation patterns, with changes potentially causing Europe to be 6-8°C cooler during glacial periods due to reductions in the