Global warming refers to the increase in the Earth's temperature caused by greenhouse gases trapping heat in the atmosphere, leading to changes in climate such as shifts in rainfall patterns and rising sea levels with major impacts on plants, animals, and humans. Carbon dioxide from sources like power plants, vehicles, buildings, and deforestation contribute to the problem, with cities like New York and Los Angeles alone emitting over 7 million tons annually from traffic congestion. Individual actions like using more efficient transportation, recycling, and choosing energy efficient appliances can help reduce greenhouse gas emissions.