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→Slowing rotation of the Earth: Melting ice caps |
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It is a mistake, however, to consider leap seconds as indicators of a slowing of Earth's rotation rate; they are indicators of the accumulated difference between atomic time and time measured by Earth rotation.<ref>{{cite web |last1=Chester |first1=Geoff |title=Wait a second… 2015 will be a little longer |url=https://www.doncio.navy.mil/chips/ArticleDetails.aspx?ID=6471 |website=CHIPS Articles: The Department of the Navy's Information Technology Magazine |date=15 June 2015|access-date=4 March 2021}}</ref> The plot at the top of this section shows that in 1972 the average length of day was approximately {{val|86400.003}} seconds and in 2016 it was approximately {{val|86400.001}} seconds, indicating an overall increase in Earth's rotation rate over that time period. Positive leap seconds were inserted during that time because the annual average length of day remained greater than {{val|86400}} SI seconds, not because of any slowing of Earth's rotation rate.<ref>{{cite web |last1=Plait |first1=Phil |title=Followup: Leap Seconds |url=https://www.discovermagazine.com/the-sciences/followup-leap-seconds |website=Discover Magazine: Bad Astronomy |date=31 December 2008|access-date=5 March 2021}}</ref>
In 2021, it was reported that Earth was spinning faster in 2020 and experienced the 28 shortest days since 1960, each of which lasted less than {{val|86399.999}} seconds.<ref>{{cite web |last1=Jones |first1=Graham |last2=Bikos |first2=Konstantin |title=Earth is in a hurry in 2020 |url= https://www.timeanddate.com/time/earth-faster-rotation.html |website=timeanddate.com |date=6 January 2021 |orig-date=2020-12-23|access-date=6 March 2021}}</ref> This caused engineers worldwide to discuss a negative leap second and other possible timekeeping measures, some of which could eliminate leap seconds.<ref>{{cite news |last1=Knapton |first1=Sarah |title=The Earth is spinning faster now than at any time in the past half century |url=https://www.telegraph.co.uk/news/2021/01/04/earth-spinning-faster-now-time-past-half-century/ |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/2021/01/04/earth-spinning-faster-now-time-past-half-century/ |archive-date=12 January 2022 |url-access=subscription |url-status=live |access-date=11 February 2021 |work=[[The Daily Telegraph]] |date=4 January 2021}}{{cbignore}}</ref> The shortest day ever recorded was 29 June 2022, at 1.59 milliseconds less than 24 hours.<ref name="NHM 270324">{{cite news |url=https://www.nhm.ac.uk/discover/news/2024/march/climate-change-causing-days-get-longer-slowing-down-earth.html |title=Climate change is causing days to get longer by slowing down the Earth |first=James |last=Ashworth |date= 27 March 2024 |publisher=Natural History Museum |___location=London}}</ref> In a 2024 paper published in [[Nature (journal)|''Nature'']], Duncan Agnew of the [[Scripps Institution of Oceanography]] projects that the water from increasing [[ice cap]] melting will migrate to the equator and thus cause the rate of rotation to slow down again.<ref name="NHM 270324" />
==Future of leap seconds==
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