There is a new paradigm about the global climate, namely that warm climates are associated with stronger, poleward-shifted westerly jets aloft and at the surface (Russell et al. 2006a in J. Climate, Russell et al. 2006b in J. Climate, Toggweiler and Russell 2008, in Nature; Toggweiler et al. 2006, in Paleoceanography). These papers finally explained the longstanding question of where and how the atmospheric carbon dioxide concentration has changed between glacial and interglacial periods. Our proposed mechanism – the positive feedback linking the position of the southern hemisphere westerlies, the ventilation of the deep Southern Ocean and the corresponding increase or decrease in atmospheric temperature and CO2 content (Toggweiler et al. 2006).
Shifts in the austral westerlies have global climatic consequences, especially through resulting changes in the greenhouse gas content of the atmosphere and altered heat flux from the tropical Pacific into the Northern and Southern Hemispheres. We suggest that the last glacial termination was a global warming episode that led to extreme seasonality in northern latitudes by stimulating a flush of meltwater and icebergs into the North Atlantic from adjoining ice sheets. This fresh-water influx resulted in widespread North Atlantic sea ice that caused very cold boreal winters, thus amplifying the annual southward shift of the Intertropical Convergence Zone and the monsoonal rain belts (Denton et al. 2021).
