Climate frequently asked questions

What’s the difference between weather and climate?

While weather and climate are closely related, they’re not the same thing.

How do we determine past climate?

Information about past climate is obtained from piecing evidence together from various sources.

What are El Niño and La Niña?

El Niño and La Niña refer to opposite extremes of the ENSO cycle, when major changes in the Pacific atmospheric and oceanic circulation occur.

What is the greenhouse effect?

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.

Has the climate changed in the past?

The Earth's climate has exhibited marked "natural" climate changes, with time scales varying from many millions of years down to a few years.

Why is there water flowing in a river when it isn’t raining?

In the absence of rain, most of the flow in a river is water that drains slowly from the ground.