Climate frequently asked questions

While weather and climate are closely related, they’re not the same thing.
Information about past climate is obtained from piecing evidence together from various sources.
El Niño and La Niña refer to opposite extremes of the ENSO cycle, when major changes in the Pacific atmospheric and oceanic circulation occur.
The greenhouse effect is a warming of the earth's surface and lower atmosphere caused by substances which let the sun's energy through to the ground but impede the passage of energy from the earth back into space.
The Earth's climate has exhibited marked "natural" climate changes, with time scales varying from many millions of years down to a few years.
In the absence of rain, most of the flow in a river is water that drains slowly from the ground.