In an article called AMO, The Key Global Climate Indicator by Matt Vooro, he discusses:
GLOBAL WARMING EXPLAINED
IPCC said that “Eleven of the last twelve years [1995-2006] rank among the twelve warmest years in the instrumental record of global surface temperature [since 1850]”
However, 13 OF THE WARMEST GLOBAL AIR TEMPERATURES happened during the 14 year period JAN 1995- DEC 2008 when PDO and AMO were essentially both warm or positive * and accounts for the global warming and the temperature records . Five of the 10 highest ANNUAL AMO levels occurred during this recent global warming period.
The numbers below show how the 3 highest monthly global temperature records were accompanied by 3 of the 5 highest single AMO index readings ever .Only 1878 and 1937 had the higher monthly AMO levels. The single PDO readings were also high [around 2.0] during these peak periods.
1998 Highest Temperature anomaly [0.546C] AMO [0.562 3rd highest]
2005 Second Highest Temperature anomaly [0 .482C] AMO [0.503 5TH highest]
2003 Third Highest Temperature anomaly [0.473C] AMO [0.504 4th Highest]
(see the figure above) there was a similar warming period in 1926-1944. So global warming existed well before manmade green house gases started to rise after the 1940’s.
As one can see
So what is the AMO?
The AMO is an ongoing series of long-duration changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 20-40 years at a time and a difference of about 1F between extremes. These changes are natural and have been occurring for at least the last 1,000 years. [per NOAA].
The AMO index is calculated at NOAAPSD by using the Kaplan (Sea Surface Temperature) SST data set [5x5], determining the area weighted average over the North Atlantic over 0-70N and then detrending this data. The average AMO index or the Atlantic Multidecadal Oscillation index went negative or cool in January 2009 The average for the first 5 months this year is about [-0.06] . It has been cooling since 2003. In the past, the very cold seasons of North America and especially the East coast happened when the annual average AMO went cool [ as low as -0.405] in the 1970’s.
It seems that this level of cool AMO may be several years off as the AMO cooling rate appears to be still slow. Back in 1964 it took about 8 years before the AMO went to [-0.3] by 1971. Review of other periods for similar rates of decline of the AMO show a spread of about 2-8 years. However the solar activity was much higher during 1964-1972 and things may cool down faster currently with extended solar minimum and anticipated low future solar cycles. If AMO does drop faster, then the cold weather like 1964-1979 may be the norm here much sooner and the East Coast will cool down as well as will the globe. The most sustained number of low AMO levels was during the cold spell of 1902 -1925 and again the 1970’s.
The graph below shows how closely Annual Global Air Temperature Anomalies [Crutem3] follow the Atlantic Multidecadal Oscillation Index [AMO] below.
The graph below shows the decline of the AMO index from warm to cool between 2005 and 2009 below.
This latest period of cooler weather is not the start of some modern ice age or new grand cold minimum but just another cool cycle of the planet that happens about after every 20-30 years more recently when AMO and PDO are both in the cool mode simultaneously. The coldest last such cycle 1902-1925 when AMO hit a single month low of -0.563 and PDO went down to -1.72 and global air temperature anomalies plummeted to -0.581C [crutem3] in 1911. Other such cool periods occurred 1964-1976 and also much earlier during the Dalton and Maunder Minimums.
A lot more information on the AMO, PDO, ENSO and NAO can be found at this link and is worth reading if you desire a deeper understanding of these major climate drivers.