Earth's temperature depends on the balance between energy entering and leaving the planet’s system. When incoming energy from the sun is absorbed by the Earth system, Earth warms. When absorbed energy is released back into space, Earth cools. Many factors, both natural and human, can cause changes in Earth’s energy balance and as a result, Earth's climate. Scientists have pieced together a record of Earth’s climate, dating back hundreds of millions of years by analyzing a number of indirect measures of climate such as ice cores, tree rings, glacier lengths, pollen remains, and ocean sediments. ITEM BANK: Move to Bottom Amount of ice/snow present on EarthChanges in Earth's orbitSolar activityVolcanic particles that reach the upper atmosphere Variations in the sun's energy reaching Earth Variations in reflectivity Both