HR: 14:15h
AN: A23A-03    [Abstracts]
TI: The NAO, the AO, and Global Warming: How Closely Related?
AU: * Cohen, J
EM: jcohen@aer.com
AF: AER, Inc., 131 Hartwell Avenue, Lexington, MA 02421 United States
AU: Barlow, M
EM: mbarlow@aer.com
AF: AER, Inc., 131 Hartwell Avenue, Lexington, MA 02421 United States
AB: The North Atlantic Oscillation (NAO) and closely related Arctic Oscillation (AO) strongly affect Northern Hemisphere (NH) surface temperatures with patterns reported similar to the global warming trend. The NAO and AO have been in a positive trend for much of the 1970s and 1980s with historic highs in the early 1990s, and it has been suggested that they contribute significantly to the global warming signal. We examine the trends in standard indices of the AO, NAO, and NH average surface temperature for Dec-Feb, 1950-2004, and the associated patterns in surface temperature anomalies. This analysis shows that the AO and NAO indices have been recently decreasing and the overall AO and NAO trends for the past thirty years are weak to non-existent, and strongly dependent on the choice of start and end date. In clear distinction, the wintertime hemispheric warming trend has been vigorous and consistent throughout the entire period. Also analyzed are factors previously identified as relating to the NAO, AO, and their positive trend: North Atlantic sea surface temperatures (SSTs), Indo-Pacific warm pool SSTs, stratospheric circulation, and Eurasian snow cover. While the NAO and AO may contribute to hemispheric and regional warming for multi-year periods, our analysis suggests that the large-scale features of the global warming trend over the last 30 years are unrelated to the AO and NAO. The other factors may also be clearly distinguished, with warm pool SSTs linked to the warming trend, while the others are linked to the NAO and AO. The results are insensitive to choice of index or dataset.
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
DE: 3322 Land/atmosphere interactions
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3362 Stratosphere/troposphere interactions
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly