Many global warming experts say the phenomenon, if unchecked, is capable of altering the world's climate and geography. In the worst-case scenario, experts say oceans could rise to overwhelming and catastrophic levels, flooding cities and altering seashores.
Other scientists and observers, a minority compared to those who believe the warming trend is something ominous, say it is simply the latest shift in the cyclical patterns of a planet's life.
Most of the scientific community believes that some warming is occurring across the globe and through some layers of the atmosphere. But why it is occurring and what that means for the future is scientifically and politically contentious.