Background
The authors write that "mid- and high-latitude crustose coralline algae are an emerging extra-tropical marine climate archive," as was demonstrated during a field calibration study (Halfar et al., 2008), since "they are amongst the longest-lived shallow marine organisms (Frantz et al., 2005)," and since "they show constant growth over their lifespan and are not subject to an ontogenetic growth trend with skeletal age."

What was done
"Using a regional network of specimens of the coralline alga Clathromorphum compactum spanning portions of the Labrador Current inshore branch from the Gulf of St. Lawrence to both latitudinal extremes of the eastern Newfoundland shelf," as Halfar et al. (2011) describe it, they generated "a 115-year-long growth-increment-width based record of subarctic northwest Atlantic surface temperatures."

What was learned
The new temperature reconstruction revealed "the well-documented regime shift and warming in the northwestern Atlantic during the 1990s." But in addition, the eight researchers report that "large positive changes in algal growth anomalies were also present in the 1920s and 1930s, indicating that the impact of a concurrent large-scale regime shift throughout the North Atlantic was more strongly felt in the subarctic Northwestern Atlantic than previously thought." And they specifically state that this regime shift "may have even exceeded the 1990s event with respect to the magnitude of the warming," as "has recently been suggested for the central and eastern North Atlantic," citing the study of Drinkwater (2006).

What it means
This study adds one more piece of evidence to the mountain of evidence, much of it coming from the Arctic, that shows warmer temperatures in the 1920s and 30s than in the late 1990s/early 2000s, as may be seen by perusing the materials we have archived in our Subject Index under the heading of Temperature Trends (Regional -- Arctic: Late Holocene), which observation is wildly at odds with the claim of the world's climate alarmists that the warming of the past two decades is unprecedented over the past millennium or more. And the fact that the air's CO2 concentration in the 1920s and 30s was on the order of 300-305 ppm does not help their cause much either, seeing that the atmosphere's CO2 concentration today is about 390 ppm, or nearly 30% greater that it was back in the 1920s and 30s.

References
Drinkwater, K. 2006. The regime shift of the 1920s and 1930s in the North Atlantic. Progress in Oceanography 68: 134-151.

Frantz, B.R., Foster, M.S. and Riosmena-Rodriguez, R. 2005. Clathromorphum nereostratum (Corallinales, Rhodophyta): the oldest alga? Journal of Phycology 41: 770-773.

Halfar, J., Steneck, R.S., Joachimski, M., Kronz, A. and Wanamaker Jr., A.D. 2008. Coralline red algae as high-resolution climate recorders. Geology 36: 463-466.