What is climate change?

Climate change is a long-term shift in the climate of a specific location, region or planet.

The shift is measured by changes in features associated with average weather, such as

temperature, wind patterns and precipitation. What most people don’t know is that a

change in the variability of climate is also considered climate change, even if average

weather conditions remain the same.

Climate change occurs when the climate of a specific area or planet is altered between

two different periods of time. This usually occurs when something changes the total

amount of the sun's energy absorbed by the earth's atmosphere and surface. It also

happens when something changes the amount of heat energy from the earth's surface

and atmosphere that escapes to space over an extended period of time.

Such changes can involve both changes in average weather conditions and changes in

how much the weather varies around these averages. The changes can be caused by

natural processes like volcanic eruptions, variations in the sun's intensity, or very slow

changes in ocean circulation or land surfaces which occur on time scales of decades,

centuries or longer.

But… humans also cause climates to change by releasing greenhouse gases and

aerosols into the atmosphere, by changing land surfaces, and by depleting the

stratospheric ozone layer. Both natural and human factors that can cause climate

change are called ‘climate forcings', since they push, or ‘force' the climate to shift to new

values.