Climate is the weather of a place averaged over a length of time. Earth's climate varies from place to place, creating a variety of environments. Thus, in various parts of Earth, we find deserts; tropical rain forests; tundras (frozen, treeless plains); conifer forests, which consist of cone-bearing trees and bushes; prairies; and coverings of glacial ice.
Climate also changes with time. For example, a thousand years ago, northern latitudes were milder than they are today. The warmer climate enabled Vikings from Iceland to settle on the southern coast of Greenland. But the colder climate that developed over the following centuries wiped out the settlements.
One major environmental concern is that human activity may be changing the global climate. The burning of fossil fuels
