 The electromagnetic radiation emitted by the sun is known as solar radiation. It provides the heat, light and energy necessary to the survival of living organisms on Earth and is the reason we need to protect our skin on sunny days like today. When the amount of solar radiation reaching the Earth changes, so does the Earth's climate. For example, with no solar radiation, the Earth would be around 30 degrees Celsius cooler than it is today. One factor that affects the amount of solar radiation reaching the Earth is the Earth's position relative to the sun. This is responsible for the long-term glacial interglacial cycles. Right now we're living in an interglacial period called the Holocene. Glacial periods are colder, dustier and generally drier than interglacial periods and large parts of the Earth are covered by ice sheets. These glacial interglacial cycles are evident in many marine and terrestrial paleoclimate records from around the world and they have waxed and waned over the past 2.6 million years. In the 1920s, Serbian scientist Milusian Milankovic examined how variations in Earth's orbital movements affect the amount of solar radiation reaching the Earth's atmosphere. The three types of movement he examined are called eccentricity, obliquity and procession.