The document discusses three main causes of climate change: 1. Earth-sun geometry - variations in the Earth's orbit, axial tilt, and precession affect the amount of solar radiation reaching Earth, according to the Milankovitch Theory. 2. Volcanic eruptions - Large eruptions can inject huge amounts of volcanic material like ash and gases into the atmosphere, reflecting sunlight back into space and lowering global temperatures for years. Major eruptions have been linked to extinction events. 3. Solar output - Small variations in the amount of energy emitted by the Sun may also influence Earth's climate on long timescales.