New paper confirms Little Ice Age was a global phenomenon, related to solar activity

A paper published today in Geophysical Research Letters confirms that "the Little Ice Age was a global event, probably caused by a change in solar [activity] and volcanic forcing [activity]." The paper finds that Greenland and Antarctica cooled synchronously, although to different magnitudes, suggesting to the authors that climate feedbacks operate differently in the Northern and Southern Hemispheres. The Little Ice Age was associated with the Maunder Minimum, a lull in solar activity that may be similar to the present. This paper corroborates other recent research showing that the Little Ice Age was a global, not local, phenomenon. According to the paper, the temperature from 1400-1800 AD in Antarctica was on average ~ 0.52C colder and Greenland ~ 1C colder than than the last 100 year average. This would imply that the 0.7C global warming since 1850 simply represents a recovery from the Little Ice Age.

GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L09710, 7 PP., 2012
doi:10.1029/2012GL051260

Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide

Key Points

• Cold interval from 1300 to 1800 C.E. at WAIS Divide
• The 1400-1800 C.E. was 0.52+/-0.28 deg C colder than the last 100 years
• Cooling broadly synchronous to Greenland cooling, with lesser amplitude

Anais J. Orsi

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

Bruce D. Cornuelle

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

Jeffrey P. Severinghaus

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

The largest climate anomaly of the last 1000 years in the Northern Hemisphere was the Little Ice Age (LIA) from 1400–1850 C.E., but little is known about the signature of this event in the Southern Hemisphere, especially in Antarctica. We present temperature data from a 300 m borehole at the West Antarctic Ice Sheet (WAIS) Divide. Results show that WAIS Divide was colder than the last 1000-year average from 1300 to 1800 C.E. The temperature in the time period 1400–1800 C.E. was on average 0.52 ± 0.28°C colder than the last 100-year average. This amplitude is about half of that seen at Greenland Summit (GRIP). This result is consistent with the idea that the LIA was a global event, probably caused by a change in solar and volcanic forcing, and was not simply a seesaw-type redistribution of heat between the hemispheres as would be predicted by some ocean-circulation hypotheses. The difference in the magnitude of the LIA between Greenland and West Antarctica suggests that the feedbacks amplifying the radiative forcing may not operate in the same way in both regions.