The term "global environment" refers to Earth's environment in general. Many environmental issues primarily affect local and national areas. Others deal with problems that face the entire planet.
Many aspects of local ecosystems are self-contained. However, global environmental factors have broad effects on regions across the globe. If the planet's temperature rises considerably, ecosystems around the world are affected. The notion of a global environment deals with how connected even distant regions are and how events in one region affect everyone. While man-made factors receive the most attention, there are a number of natural factors as well. Volcanic eruptions, for example, can affect the entire planet.
Many environmental issues deal with local problems faced by nations and smaller communities. Particulate pollution, for example, tends to affect a metropolitan area but spread no further. Particulate matter in Chinese cities only affects people living near factories and power plants.
The carbon dioxide produced by these factories and plants, however, has a worldwide effect. Carbon dioxide spreads throughout the atmosphere, and the warming produced by carbon dioxide affects places around the world. Often, people neglect the impact that land-based actions have on the oceans. If the Gulf Stream or other streams of water in the ocean are disrupted, however, the effects are profound.