Global warming refers to an unequivocal and continuing rise in the average temperature of Earth's climate system.[2] Since 1971, 90% of the warming has occurred in the oceans.[3] Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface.[4][5] Since the early 20th century, the global air and sea surface temperature has increased about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980.[6] Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.[7]