TITLE:
Multi-Decadal Trends of Global Surface Temperature: A Broken Line with Alternating ~30 yr Linear Segments?
AUTHORS:
Vincent Courtillot, Jean-Louis Le Mouël, Vladimir Kossobokov, Dominique Gibert, Fernando Lopes
KEYWORDS:
Global Surface Temperature; Multi-Decadal Evolution; Linear Segments; ~60-Year Oscillation
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.3 No.3,
July
8,
2013
ABSTRACT:
We investigate global temperature data produced by the Climate Research Unit at the University of East Anglia (CRU) and the Berkeley Earth Surface Temperature consortium (BEST). We first fit the 1850-2010 data with polynomials of degrees 1 to 9. A significant ~60-yr oscillation is accounted for as soon as degree 4 is reached. This oscillation is even better modeled as a broken line, more precisely a series of ~30-yr long linear segments, with slope breaks (singularities) in ~1904, ~1940, and ~1974 (±3 yr), and a possible recent occurrence at the turn of the 20th century. Oceanic indices PDO (Pacific Decadal Oscillation) and AMO (Atlantic Multidecadal Oscillation) have undergone major changes (respectively of sign and slope) roughly at the same times as the temperature slope breaks. This can be interpreted with a system of oceanic non-linear coupled oscillators with abrupt mode shifts. Thus, the Earth’s climate may have entered a new mode (a new ~30-yr episode) near the turn of the 20th century: no further temperature increase, a dominantly negative PDO index and a decreasing AMO index might be expected for the next decade or two.