I know it's a risk making trend lines, but those of us who work with clocks, oscillators and frequency standards find it irresistible to peek ahead sometimes and guess what's coming. This applies to my favorite clock, the earth.
See attached inverse length of day plots (that is, frequency error rather than excess LOD, or period error). This started with Stable32 (the standard tool we all use for time & frequency metrology) but I reformatted them with Excel to make them clearer. This plot is for 1 July 1972 to the present. Those of you who follow DUT1 like the stock market recognize the characteristic periodicity, bumps, and trends. Note especially the stable period starting 1999, with many days of the year longer than 86400 seconds, and consequently no leap second for 7 years (roughly MJD 51000 to 54000). Any betting person would say the plot shows an upward trend over the past 40 years. A simple linear fit suggests the earth will be back to an honest 86400 second day within a few years, around MJD ~59000 (year ~2020). The URL for the plot is: http://leapsecond.com/pages/lod/earth-lod-10.gif See also the zoomed version, where the predicted zero-crossing is clearer: http://leapsecond.com/pages/lod/earth-lod-11.gif The raw DUT1 and LOD data comes from IERS. It's a work in progress; other plots are under http://leapsecond.com/pages/lod/ as I pursue this. I realize this is just for fun, and the serious geology, astronomy, and climate professionals on the list will raise valid concerns. But there's no doubt that since the 1970's the earth is generally speeding back up. If this trend continues, within a decade, we will have another long stretch of no leap seconds and this time it will be followed by our first negative leap second. /tvb
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