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] 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.[5] Each
of the last three decades has been successively warmer at the Earth's surface
than any preceding decade since 1850.[6]
Scientific understanding of the cause of global warming has been increasing.
In its fourth assessment (AR4 2007) of the relevant scientific literature, the International Panel on Climate Change (IPCC)
reported that scientists were more than 90% certain that most of global warming
was being caused by increasing concentrations of greenhouse gases produced by human
activities.[7][8][9] In
2010 that finding was recognized by the national science academies of all major
industrialized nations.[10][A] Affirming these findings in
2013, the IPCC stated that the largest driver of global warming is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production, and land use changes such as deforestation.[11] Its
2013 report states
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] 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.[5] Each
of the last three decades has been successively warmer at the Earth's surface
than any preceding decade since 1850.[6]
Scientific understanding of the cause of global warming has been increasing.
In its fourth assessment (AR4 2007) of the relevant scientific literature, the International Panel on Climate Change (IPCC)
reported that scientists were more than 90% certain that most of global warming
was being caused by increasing concentrations of greenhouse gases produced by human
activities.[7][8][9] In
2010 that finding was recognized by the national science academies of all major
industrialized nations.[10][A] Affirming these findings in
2013, the IPCC stated that the largest driver of global warming is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production, and land use changes such as deforestation.[11] Its
2013 report states