On Sat 2024-03-30T16:03:30-0700 Paul Hirose hath writ: > "Even a few years ago, the expectation was that leap seconds would always be > positive, and happen more and more often," Duncan Agnew, a geophysicist at
The paper in Nature takes a very narrow view of history. Agnew looks only at data in IERS C04. That started in 1962 because 1) There were no available atomic time scales until the middle of year 1961, so earlier earth rotation data were less precise https://www.ucolick.org/~sla/leapsecs/taiepoch.html 2) The IAU had resolved that 1962-01-01 would be the date to change from using the FK3 star catalog to using the FK4 star catalog, and as noted in my TAI web page above that caused a discontinuity in the value of time. 3) Although coordinated time existed before, it was 1962-01-01 when BIH Paris was put in charge of what they would later name UTC. 4) The early atomic time scales from BIH were computed entirely by hand. The published values show arithmetic errors which were never corrected. With BIH perennially understaffed going back farther in time would incorporate more such errors into C04. With C04 there is only one point at which the core of the earth made one of its huge shifts in angular momentum, and that was coincidentally right around 1972. Agnew further restricts his analysis to only the earth rotation after 1972. Agnew is certainly correct that melting ice caps are slowing the rotation of the surface of the earth. With the acceleration being caused by whatever the core has been doing for the past 50 year Agnew is also correct that the meltwater is delaying the need for a negative leap second. But the analysis by Agnew is blind to the long history of big changes in the core. I think that is why Matsakis is quoted in one of the news articles about not betting on predictions of earth rotation. Also do not forget McCarthy and Matsakis previously looking at the trend https://insidegnss.com/will-we-have-a-negative-leap-second/ -- Steve Allen <[email protected]> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m _______________________________________________ LEAPSECS mailing list [email protected] https://pairlist6.pair.net/mailman/listinfo/leapsecs
