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Monthly AMO Drops Negative, Will It Persist, What Will It Mean?

By Joe D'Aleo
Monday, March 16, 2009

The AMO has been in decline since peaking in late 2003-2005.



Normally the warm and cold phases of the AMO each last roughly three decades. It appeared the last warm phase tried to get going in 1988 but Pinatubo put a damper on the warming delaying it till 1995. If 1988 is the real starting point, then it should last until 2018.


But a quiet sun amplified the decline near the turn of the prior century (late 1800s) and again after quiet cycle 20 in the 1960s to mid 1970s. Could this super quiet sun (see last week’s post) be causing a premature drop in AMO or is it just a normal variability.



Last may, we posted a story on the importance of the AMO to hurricanes, the NAO and US and arctic temperatures.


A warm AMO leads to above normal hurricane activity in the Atlantic, and except dring El Nino summers, more major hurricanes and more landfalls.



The AMO leads to warmer temperatures not only in the Atlantic but most continental areas in the Northern Hemisphere.



We noted in the prior story that the PDO favors more El Ninos and more global warmth. A positive PDO and positive AM) produce the most warmth and the negative AMO and negative PDO, cooling.



Given that the sun also correlates with temperatures, we see a very good matching of annual solar, AMO+PDO with U.S. temperatures.




The AMO has dipped into negative territory. The PDO has been strongly negative the last few years..The combination of the two correlate well with U.S.temperatures. A solar temperature relationship also exists. The three together suggests cooling ahead. A recent paper
in Discovery supports this trend towards cooling which the authors suggest could last 30 years.


As for the hurricane season, if AMO were stay negative, it would counter the enhancement from antecedent La Nina conditions. I would guess the AMO will return slightly positive and the season will have again normal to above normal activity 12-14 named storms, 7 hurricanes and 2 major systems. With the cold PDO, east coast and Gulf Coast are both vulnerable to landfall. Read this relationship of oceans with hurricanes story here. More later.