What is climate change?
The term climate refers to the general weather conditions of a place over many years. In the United States, for example, Maine’s climate is cold and snowy in winter while South Florida’s is tropical year-round. Climate change is a significant variation of average weather conditions—say, conditions becoming warmer, wetter, or drier—over several decades or more. It’s that longer-term trend that differentiates climate change from natural weather variability. And while “climate change” and “global warming” are often used interchangeably, global warming—the recent rise in the global average temperature near the earth’s surface—is just one aspect of climate change.
How is climate change measured over time?
Earth-orbiting satellites, remote meteorological stations, and ocean buoys are used to monitor present-day weather and climate, but it’s paleoclimatology data from natural sources like ice cores, tree rings, corals, and ocean and lake sediments that have enabled scientists to extend the earth’s climatic records back millions of years. These records provide a comprehensive look at the long-term changes in the earth’s atmosphere, oceans, land surface, and cryosphere (frozen water systems). Scientists then feed this data into sophisticated climate models that predict future climate trends—with impressive accuracy.
What causes climate change?
The mechanics of the earth’s climate system are simple. When energy from the sun is reflected off the earth and back into space (mostly by clouds and ice), or when the earth’s atmosphere releases energy, the planet cools. When the earth absorbs the sun’s energy, or when atmospheric gases prevent heat released by the earth from radiating into space (the greenhouse effect), the planet warms. A variety of factors, both natural and human, can influence the earth’s climate system.