Redigerer Global oppvarming (avsnitt)

=== Variasjoner i jordas bane ===
{{Hoved|Milanković-syklusene}}

Hellingen av jordaksen og formen på jordens bane rundt solen varierer noe over titusener av år. Dette endrer klimaet ved å endre årstider og fordelingen av innkommende [[Solinnstråling|solenergi]] etter breddegrad på jordoverflaten.<ref>{{Cite journal
|last1 = Kaufman | first1 = D. S.| last2 = Schneider | first2 = D. P.| last3 = McKay | first3 = N. P.| last4 = Ammann | first4 = C. M.| last5 = Bradley | first5 = R. S.| last6 = Briffa | first6 = K. R.| last7 = Miller | first7 = G. H.| last8 = Otto-Bliesner | first8 = B. L.| last9 = Overpeck | first9 = J. T.| last10 = Vinther | first10 = B. M.| author32 = Arctic Lakes 2k Project Members| last11 = Abbott | first11 = M.| last12 = Axford | first12 = M.| last13 = Bird | first13 = Y.| last14 = Birks | first14 = B.| last15 = Bjune | first15 = H. J. B.| last16 = Briner | first16 = A. E.| last17 = Cook | first17 = J.| last18 = Chipman | first18 = T.| last19 = Francus | first19 = M.| last20 = Gajewski | first20 = P.| last21 = Geirsdottir | first21 = K.| last22 = Hu | first22 = A.| last23 = Kutchko | first23 = F. S.| last24 = Lamoureux | first24 = B.| last25 = Loso | first25 = S.| last26 = MacDonald | first26 = M.| last27 = Peros | first27 = G.| last28 = Porinchu | first28 = M.| last29 = Schiff | first29 = D.| last30 = Seppa | first30 = C.| last31 = Seppa | first31 = H.| title = Recent Warming Reverses Long-Term Arctic Cooling| doi = 10.1126/science.1173983| journal = Science| volume = 325| issue = 5945| pages = 1236–1239| year = 2009| pmid =  19729653|bibcode = 2009Sci...325.1236K }}</ref><ref>{{cite web |title=Arctic Warming Overtakes 2,000 Years of Natural Cooling |url=http://www2.ucar.edu/news/846/arctic-warming-overtakes-2000-years-natural-cooling |publisher=UCAR |date=3. september 2009 |accessdate=8. juni 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20110427235538/http://www2.ucar.edu/news/846/arctic-warming-overtakes-2000-years-natural-cooling |archivedate=2011-04-27 }}</ref><ref>{{Cite news | last =Bello | first = David | title = Global Warming Reverses Long-Term Arctic Cooling | url = http://www.scientificamerican.com/article.cfm?id=global-warming-reverses-arctic-cooling | work=Scientific American | date = 4. september 2009 | accessdate =8. juni 2011}}</ref><ref>{{Cite journal | last1 = Mann | first1 = M. E. | last2 = Zhang | first2 = Z. | last3 = Hughes | first3 = M. K. | last4 = Bradley | first4 = R. S. | last5 = Miller | first5 = S. K. | last6 = Rutherford | first6 = S. | last7 = Ni | first7 = F. | doi = 10.1073/pnas.0805721105 | title = Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia | journal = Proceedings of the National Academy of Sciences | volume = 105 | issue = 36 | pages = 13252–7 | year = 2008 | pmid =  18765811| pmc = 2527990|bibcode = 2008PNAS..10513252M }}</ref> Banesykluser som er gunstig for å gi istid, er ikke ventet i løpet av de neste 50 000 årene.<ref>{{Cite journal | doi = 10.1126/science.1076120| title = CLIMATE: An Exceptionally Long Interglacial Ahead?| journal = Science| volume = 297| issue = 5585| pages = 1287–8| year = 2002| last1 = Berger | first1 = A.| pmid=12193773}}</ref><ref>{{Cite book
|isbn=978-1-107-66182-0|title=Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change
|year=2013|publisher=Cambridge University Press|editors=Stocker T.F. |display-editors=etal
|chapter=Information from paleoclimate archives|author=Masson-Delmotte V.M.|pages=383–464
|display-authors=etal}}</ref>