Editing Climate variability and change (section)

==== Ocean current changes ====
{{See also|Thermohaline circulation}}
[[File:Ocean circulation conveyor belt.jpg|thumb|right|upright=1.35|A schematic of modern [[thermohaline circulation]]. Tens of millions of years ago, continental-plate movement formed a land-free gap around Antarctica, allowing the formation of the [[Antarctic Circumpolar Current|ACC]], which keeps warm waters away from Antarctica.]]
The oceanic aspects of climate variability can generate variability on centennial timescales due to the ocean having hundreds of times more mass than in the [[Atmosphere of Earth|atmosphere]], and thus very high [[thermal inertia]]. For example, alterations to ocean processes such as thermohaline circulation play a key role in redistributing heat in the world's oceans.

Ocean currents transport a lot of energy from the warm tropical regions to the colder polar regions. Changes occurring around the last ice age (in technical terms, the last [[glacial period]]) show that the circulation in the [[North Atlantic]] can change suddenly and substantially, leading to global climate changes, even though the total amount of energy coming into the climate system did not change much. These large changes may have come from so called [[Heinrich events]] where internal instability of ice sheets caused huge ice bergs to be released into the ocean. When the ice sheet melts, the resulting water is very low in salt and cold, driving changes in circulation.{{sfn|Burroughs|2001|pp=207–08}}