Improved understanding of secular variation of Earth's magnetic field, and core structure and dynamics, including quantification of rapid field decrease that may signal a reversal of the Earth's field. (polenet.org)
On the basis of these observations we conclude that class I excursions, epitomized by the Laschamp Excursion, are more closely related to normal secular variation and are not necessarily a prelude to magnetic field reversal.» (realclimate.org)
The hockey stick attempted to wipeout secular variations prior to the 20th century, but even Mike's Nature trick spliced the early 20th century warming as an integral part of the blade. (judithcurry.com)