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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D12108, doi:10.1029/2004JD005686, 2005

AO/NAO response to climate change: 2. Relative importance of low- and high-latitude temperature changes

D. Rind

NASA Goddard Institute for Space Studies at Columbia University, New York, New York, USA


J. Perlwitz

NASA Goddard Institute for Space Studies at Columbia University, New York, New York, USA


P. Lonergan

NASA Goddard Institute for Space Studies at Columbia University, New York, New York, USA


J. Lerner

NASA Goddard Institute for Space Studies at Columbia University, New York, New York, USA


Abstract

We address the issue of why different models may be getting different responses of the AO/NAO in climate change experiments. The results from part 1 (Rind et al., 2005) suggest that for substantive climate changes, the differences are likely to be found in the patterns of tropospheric climate change, rather than from the stratosphere. We assess the various tropospheric forcings through a variety of experiments. We first use extreme paleoclimate experiments (Ice Age, Paleocene) which feature large variations in the low level latitudinal temperature gradient; the results show that under these circumstances, changes in the eddy transport of sensible heat, and in situ high latitude forcing, dominate the AO response. We next test the effect of more modest SST temperature gradient changes in the current climate, and find a similar result with a model configuration that does not easily transport the low level temperature changes into the upper troposphere. We then reanalyze the results from different 2 × CO2 experiments with the GISS model and find that they can be understood by assessing: (1) the magnitude of tropical SST warming; (2) the translations of that warming into the upper troposphere; (3) the change in the extratropical low altitude temperature gradient; and (4) the change in the high latitude SST/sea ice response. We suggest that these features might explain the varying results among modeling groups, and that forecasts will not converge until these features do.

Received 10 December 2004; accepted 14 April 2005; published 21 June 2005.

Keywords: Arctic Oscillation; climate change; temperature gradient.

Index Terms: 1620 Global Change: Climate dynamics (0429, 3309); 3319 Atmospheric Processes: General circulation (1223); 3349 Atmospheric Processes: Polar meteorology; 3344 Atmospheric Processes: Paleoclimatology (0473, 4900); 3362 Atmospheric Processes: Stratosphere/troposphere interactions.

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Citation: Rind, D., J. Perlwitz, P. Lonergan, and J. Lerner (2005), AO/NAO response to climate change: 2. Relative importance of low- and high-latitude temperature changes, J. Geophys. Res., 110, D12108, doi:10.1029/2004JD005686.