Attributing global warming to extreme weather events
Ten years ago, looking at climate issues from a scientific perspective, trying to attribute global warming to a specific Category 3 hurricane in the North Atlantic [such as Hurricane Sandy, which affected New York City in 2012] would be considered risky.
Today, it is clear that in the last century, the Earth's oceans absorbed solar energy that had not returned to the atmosphere. As a result, the average temperature of the ocean is rising. Climate scientists are studying how global warming affects extreme weather events in certain geographic regions. Swanson  summarizes the concept of the relationship between the greenhouse effect, global warming and extreme weather events, pointing out that the possibility of these extreme weather events is closely related to anthropogenic global warming – too much carbon dioxide is emitted into the atmosphere. This is no longer an abstract concept. It can be felt at all levels. 
Global warming and melting of Arctic glaciers
The temperature in the Arctic Ocean has been rising due to global warming. This higher temperature extends the summer melt of the Arctic ice to the autumn and winter. The Arctic, previously covered by white reflections of snow, has now been replaced by dark land and seas that cannot reflect sunlight. Jay Zwall of NASA's Goddard Space Flight Center estimates the amount of glacier mass loss in Greenland, pointing out that "20% more ice" appears from the snowfall received each year. Biello   Given that the sun is no longer reflected, this energy is now absorbed by the ocean, causing the ocean to warm and strengthen the melting effect of the Arctic ice shelf.
This melting is causing significant changes in the rapids [small, fast-moving westerly flows from west to east in the United States, Canada, Europe, and northern Asia], which is the most important pressure [difference] gradient in the atmosphere affecting the mid-latitudes of the North. Regional winter weather.
The fundamental change in Jet Stream is caused by global warming
The jet may be seen as a wave moving in the middle of the northern hemisphere and a wave in the valley, curved smoothly in the north and south. The temperature gradient [difference] between the Arctic latitude and the North Atlantic latitude decreases during the fall, when the Arctic Ocean releases additional solar energy absorbed by incremental ice melting from global warming. Then, the difference in air pressure between the two pressure fields is also reduced, and the velocity of the jet west-east wind is also reduced.
There are two pressure fields in the northern hemisphere. Arctic Oscillation, or AO, from the 70° north latitude to the north parallel parallel positive or negative pressure field, the North Atlantic Oscillation, or NAO, from the positive or negative pressure field parallel to the 70° north latitude to the subtropical zone. Now, given that the NAO pressure field affected by global warming is more likely to be negative in the fall and winter, it is more likely to change Jet Stream in winter.
2011-2012 Extremely warm America and cold European winter
As mentioned earlier, global warming has an impact on the extent to which Arctic ice melts. The sun's energy is absorbed by the ocean during the summer, and then this heat is expelled by the Arctic Sea in the fall, reducing the pressure [difference] gradient between the Arctic Oscillation pressure field and the North Atlantic Oscillation. Pressure field, Jet Stream deceleration. The pressure gradient between AO and NAO becomes weak, making it easier for larger jets to bend north or south.
In the winter of 2011-2012, temperatures in the northeastern United States were abnormally warming. In the northeastern states of the United States, the jets bend northward farther than usual, allowing subtropical warm air to extend north to the US-Canada border and where it stays for a long time. In addition, LaNiña [which means pressure oscillations originating in the South Pacific] also exists. This climatic phenomenon tends to cause Jet Stream to deviate north from the northeastern United States.
At the same time, in Eastern Europe, the coldest winter in 25 years occurred between 2011 and 2012. The pressure gradient [difference] between NA and NAO is weak because the extra heat released by the ocean in the fall comes from the melting of the Arctic ice caused by global warming. The jet extends southward, causing the Arctic air to reach Eastern Europe and lock it there for a longer period of time, producing a large percentage of freezing. Fischetti  summarizes this and shows that as more Arctic ice melts in summer, this will result in longer Jet Stream corners and the longer they stay in place, making winter warmer than usual or It's colder. 
There is no normal winter anymore.
Scientists are investigating how Arctic ice masses are melting due to global warming. The question now is: Why does the Arctic ice melt faster than computer models can predict global warming?
As global warming continues, the process of melting Arctic ice and its impact on the northern hemisphere pressure field may continue to push the Arctic or Antarctic rapids. Normal, regular winter will no longer be the norm.
Author: Alfonso de Garay
 Swanson, Jeanene. 2013. “Cloudy, typhoon opportunities”, Storm Warning: Climate Change and Extreme Weather, Editor of Scientific American, 12/11/13 eBook
 Bielo, David. year 2006. "The glaciers in Greenland are leaving, go…"
Scientific American Online, October 19, 2006
 Fiskety, Mark. 2012. "The northern hemisphere may enter extreme winter"
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