In addition to the role it plays in driving the water cycle and affecting climate and weather, the energy received from the sun also makes possible the process of photosynthesis, which maintains the atmospheric levels of oxygen required for aerobic organisms to exist on Earth. The light energy captured by plants through photosynthesis is also the source of the energy stored in the organic compounds that provide the greater portion of the energy required for multicellular life to continue. The solar energy stored in fossil fuels and released through burning for human use represents another important role played by sunlight.
The water cycle, which makes possible the transfer of water from oceans to land, is powered by sunlight. The weather conditions that move water through the stages of evaporation, condensation and precipitation are all direct results of the heating action of the sun's rays.