Researchers from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts are studying the growth layers of Beremuda Brain Coral to to determine the long-term behavior of the North Atlantic Oscillation (NAO). The NAO is a very important driver of climate fluctuations in the North Atlantic and is certainly a major influence on the weather in North America and Western Europe, especially during the winter months. What they found is quite interesting.
Excerpts from the WHOI press release below..........
"Because they (coral) are slow growing and have long life-spans, corals can provide high resolution records that are well dated and centuries long", said Nathalie Goodkin, lead author of the study.
The team found the variability of the NAO decade-to-decade (multi-decadal scale) has been larger, swinging more wildly, during the late twentieth century than in the early 1800s, suggesting that variability is linked to the mean temperature of the Northern Hemisphere.
"When the Industrial Revolution begins and atmospheric temperature becomes warmer, the NAO takes on a much stronger pattern in longer-term behavior," said Goodkin. "That was suspected before in the instrumental records, but this is the first time it has been documented in records from both the ocean and the atmosphere."
"Anthropogenic (human-related) warming does not appear to be altering whether the NAO is in a positive or negative phase at multi-decadal time scales," said WHOI paleoclimatologist Konrad Hughen. "It does seem to be increasing variability. Clearly, this has implications for the future."
"As temperatures get warmer, there's potential for more violent swings of the NAO -- the phases becoming even more positive and even more negative," Hughen added. "If the NAO locks more into these patterns, intense storms will become more intense and droughts will become more severe."
The WHOI has an an interesting graph showing the longer term variability of the NAO and how it is related to the warming.
Also, here is the update plot of the NAO index going back to 1950, courtesy of NOAA.....