Editing Climate variability and change (section)

==== Sea ice ====
[[Sea ice]] plays an important role in Earth's climate as it affects the total amount of sunlight that is reflected away from the Earth.<ref>{{Cite journal|last1=Belt|first1=Simon T.|last2=Cabedo-Sanz|first2=Patricia|last3=Smik|first3=Lukas|last4=Navarro-Rodriguez|first4=Alba|last5=Berben|first5=Sarah M. P.|last6=Knies|first6=Jochen|last7=Husum|first7=Katrine|display-authors=3|date=2015|title=Identification of paleo Arctic winter sea ice limits and the marginal ice zone: Optimised biomarker-based reconstructions of late Quaternary Arctic sea ice|journal=Earth and Planetary Science Letters|volume=431|pages=127–39|doi=10.1016/j.epsl.2015.09.020|bibcode=2015E&PSL.431..127B|issn=0012-821X|hdl=10026.1/4335|hdl-access=free}}</ref> In the past, the Earth's oceans have been almost entirely covered by sea ice on a number of occasions, when the Earth was in a so-called [[Snowball Earth]] state,<ref>{{Cite journal|last1=Warren|first1=Stephen G.|last2=Voigt|first2=Aiko|last3=Tziperman|first3=Eli|last4=Sadler|first4=Peter M.|last5=Rose|first5=Catherine V.|last6=Rose|first6=Brian E. J.|last7=Ramstein|first7=Gilles|last8=Partin|first8=Camille A.|last9=Maloof|first9=Adam C.|display-authors=3|date=1 November 2017|title=Snowball Earth climate dynamics and Cryogenian geology-geobiology|journal=Science Advances|volume=3|issue=11|pages=e1600983|doi=10.1126/sciadv.1600983|pmid=29134193|issn=2375-2548|pmc=5677351|bibcode=2017SciA....3E0983H}}</ref> and completely ice-free in periods of warm climate.<ref>{{Cite journal|last1=Caballero|first1=R.|last2=Huber|first2=M.|date=2013|title=State-dependent climate sensitivity in past warm climates and its implications for future climate projections|journal=Proceedings of the National Academy of Sciences|volume=110|issue=35|pages=14162–67|doi=10.1073/pnas.1303365110|pmid=23918397|pmc=3761583|bibcode=2013PNAS..11014162C|issn=0027-8424|doi-access=free}}</ref> When there is a lot of sea ice present globally, especially in the tropics and subtropics, the climate is [[Climate sensitivity|more sensitive to forcings]] as the [[ice–albedo feedback]] is very strong.<ref>{{Cite journal|last1=Hansen James|last2=Sato Makiko|last3=Russell Gary|last4=Kharecha Pushker|date=2013|title=Climate sensitivity, sea level and atmospheric carbon dioxide|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=371|issue=2001|pages=20120294|doi=10.1098/rsta.2012.0294|pmc=3785813|pmid=24043864|arxiv=1211.4846|bibcode=2013RSPTA.37120294H}}</ref>