Earth's atmosphere consists mostly of nitrogen and oxygen. More solar energy is received by tropical regions than polar regions, and is redistributed by atmospheric and ocean circulation. Greenhouse gases also play an important role in regulating the surface temperature. A region's climate is not only determined by latitude, but also by elevation, and by proximity to moderating oceans, among other factors. Extreme weather, such as tropical cyclones and heat waves, occurs in most areas and has a large impact on life.