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The Arctic Oscillation (AO) and the Antarctic Oscillation (AAO) are the leading modes of high-latitude variability in each hemisphere as characterized by the first EOF of mean sea-level pressure. Observations suggest a recent positive trend in the AO and it is speculated that this may be related to global warming. The CCCma coupled general circulation model(More)
The ability of 15 atmospheric general circulation models (AGCM) to simulate the tropical intrasea-sonal oscillation has been studied as part of the Atmospheric Model Intercomparison Project (AMIP). Time series of the daily upper tropospheric velocity poential and zonal wind, averaged over the equatorial belt, were provided from each A G C M simulation.(More)
  • Co-Ordinating Lead, Authors F Giorgi, B Hewitson, J Christensen, M Hulme, H Von Storch +52 others
  • 2001
Executive Summary Introduction This chapter assesses regional climate information from Atmosphere-Ocean General Circulation Models (AOGCMs) and techniques used to enhance regional detail. These techniques have been substantially improved since the IPCC WGI Second Assessment Report (IPCC, 1996) (hereafter SAR) and have become more widely applied. They fall(More)
Over the past half-century, the ozone hole has caused a poleward shift of the extratropical westerly jet in the Southern Hemisphere. Here, we argue that these extratropical circulation changes, resulting from ozone depletion, have substantially contributed to subtropical precipitation changes. Specifically, we show that precipitation in the southern(More)
Recent observed global warming is significantly less than that simulated by climate models. This difference might be explained by some combination of errors in external forcing, model response and internal climate variability. G lobal mean surface temperature over the past 20 years (1993–2012) rose at a rate of 0.14 ± 0.06 °C per decade (95% confidence(More)
A nonlinear generalisation of Principal Component Analysis (PCA) is applied to the 500mb geopotential height field of the Northern Hemisphere extratropical atmosphere. It is found that the low-frequency variability of the mid-troposphere is characterised by three distinct quasi-stationary states. The states are described and compared to those obtained from(More)
A global, flux-corrected climate model is employed to predict the surface wind stress and associated wind-driven oceanic circulation for climate states corresponding to a doubling and quadrupling of the atmospheric CO 2 concentration in a simple 1% per year CO 2 increase scenario. The model indicates that in response to CO 2 increase, the position of zero(More)
[1] I show that the latest series of climate models reproduce the observed mid-depth Southern Ocean warming since the 1950s if they include time-varying changes in anthropogenic greenhouse gases, sulphate aerosols and volcanic aerosols in the Earth's atmosphere. The remarkable agreement between observations and state-of-the art climate models suggests(More)