Warmer winters will bring more wet weather to Europe and Western North America, Shindell said, with Western Europe the worst hit by storms coming off the Atlantic. Using a computer climate model to try and understand where the warming over the past three decades is coming from, Shindell and colleagues discovered that in the model, increasing greenhouse gases cause stronger spiraling winds over the North Pole, a phenomenon called the polar vortex, that change the normal Northern Hemisphere climate. It's a big concern to know why this happens. The normal Northern Hemisphere climate is run by a system similar and second in size to El Nino. The pressure system, called the Arctic Oscillation, and encompassing the more familiar North Atlantic Oscillation, is the reason why some winters are much colder or more severe than others.
Air picks up heat as the winds blow over the oceans.
The ocean retains heat much better than the land. Thus, warm air from the Pacific Ocean warms Western North America and Atlantic Ocean warmth is shared with the Eurasian continent. The stronger the wind, the warmer the winter. At other times, the winds become weak, and winters become much colder. The flip-flop from cold to warm happens every few years, according to Shindell.