claim: Temperatures in 1999 were nearly three-tenths of a degree lower than in 1998, and a similar change should occur this time around, though it might not fit so neatly into a calendar year.
evidence: Because 97 out of 400 years are leap years, the mean length of the Gregorian calendar year is 365.2425 days; with a relative error below one ppm ( 8·10−7 ) relative to the current length of the mean tropical year ( 365.24219 days ) and even closer to the current March equinox year of 365.242374 days that it aims to match.