The document discusses Earth's hydrosphere and the water cycle. It explains that energy from the sun drives evaporation from surfaces like oceans, rivers, and soil. This water vapor then condenses to form clouds, which absorb infrared radiation in the atmosphere. Pumping groundwater increases the amount of water in the hydrosphere that is subject to evaporation and transpiration, adding to cloud cover and influencing the climate system, though the exact impacts are still being studied. The total mass of Earth's hydrosphere is about 1.4×1018 tonnes, with about 75% of the surface covered by oceans with an average salinity of 35 grams of salt per kilogram of seawater.