Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global temperatures is well outside of the Earth’s cyclic norms, and evidence for human-caused global climate change is compelling. Paleoclimatology, the study of ancient climate conditions, provides ample evidence for human-caused global climate change by comparing recent conditions with those in the past.

Climate refers to the prevailing weather conditions in a specific area over an extended period. As the saying goes, “Climate is what you expect. Weather is what you get.” Climate is influenced by geographic factors, such as latitude, terrain, and proximity to bodies of water.

Water Cycle The water cycle describes how water continuously moves through the Earth's atmosphere, surface, and underground layers. This process includes evaporation, condensation, precipitation, infiltration, and runoff. The sun drives the cycle by providing energy for evaporation, while gravity moves water through systems and returns it to bodies of water. The water cycle is essential for replenishing freshwater sources, supporting ecosystems, and regulating climate. Scientists can better...

Change of State: Condensation, Sublimation, and DepositionMatter changes from one state to another when heat is added or removed. Condensation, sublimation, and deposition are three phase changes that occur due to variations in temperature and pressure.Condensation happens when a gas turns into a liquid, such as water vapor, forming dew.Sublimation occurs when a solid changes directly into a gas without becoming a liquid, like dry ice, which turns into carbon dioxide gas.Deposition is the...

Overview

Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.