Background
The authors note that "about 850,000 years ago, the period of the glacial cycles changed from 41,000 to 100,000 years," and that "this mid-Pleistocene climate transition has been attributed to global cooling, possibly caused by a decrease in atmospheric carbon dioxide concentrations (Berger et al., 1999; Raymo, 1997)."  However, they say that "evidence for such cooling is currently restricted to the cool upwelling regions in the eastern equatorial oceans (Marlow et al., 2000; Liu and Herbert, 2004)," even though it is the tropical warm pools on the western sides of the ocean basins that "are particularly sensitive to changes in radiative forcing (Lea, 2004; Broccoli, 2000)," such as that which is believed by many to be caused by changes in the air's CO2 concentration.

What was done
In further exploring this subject, de Garidel-Thoron et al. present what they describe as "high-resolution records of sea surface temperatures spanning the past 1.75 million years, obtained from oxygen isotopes and Mg/Ca ratios in planktonic foraminifera from the western Pacific warm pool."

What was learned
The four scientists report that "in contrast with the eastern equatorial regions, sea surface temperatures in the western Pacific warm pool [were] relatively stable throughout the Pleistocene epoch, implying little long-term change in the tropical net radiation budget."

What it means
de Garidel-Thoron et al. conclude that their data "challenge the hypothesis of a gradual decrease in atmospheric carbon dioxide concentrations as a dominant trigger of the longer glacial cycles since 850,000 years ago."  As for the implications of their findings for climate-alarmist claims of impending CO2-induced global warming, they can only detract from them.

References
Berger, A., Li, X.S. and Loutre, M.-F.  1999.  Modelling northern hemisphere ice volume over the last 3 Ma.  Quaternary Science Reviews 18: 1-11.

Broccoli, A.J.  2000.  Tropical cooling at the last glacial maximum: an atmosphere-mixed layer ocean model simulation.  Journal of Climate 13: 951-976.

Lea, D.W.  2004.  The 100,000 year cycle in tropical SST, greenhouse forcing, and climate sensitivity.  Journal of Climate 17: 2170-2179.

Liu, Z. and Herbert, T.D.  2004.  High-latitude influence on the eastern equatorial Pacific climate in the early Pleistocene epoch.  Nature 427: 720-723.

Marlow, J.R., Lange, C.B., Wefer, G. and Rosell-Mele, A.  2000.  Upwelling intensification as part of the Pliocene-Pleistocene climate transition.  Science 290: 2288-2291.

Raymo, M.E.  1997.  The timing of major climate terminations.  Paleoceanography 12: 577-585.