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Question: We just got back from a vacation in Lund, Sweden. Why are Lund's winter temperatures similar to Binghamton's even though Lund is much farther north?
The answer to this deals with more than just latitude, such as north and south. If the earth was just a ball of solid matter this situation would not be as you describe it. However, more of the earth's surface is covered by water than by land. This and the fact that the earth spins while moving in its orbit around the sun, helps to answer this questions.
When sunlight hits the earth, soil, plants and water absorb some of its energy. A lot of this energy is re-radiated as microwaves, more or less quickly depending on the material involved. The re-radiated energy helps to warm the air at night. Water retains the absorbed energy longer than other materials, and so it becomes warmer from this energy than other materials during any given period of time. This allows it to release energy into the air all though the night. Furthermore, water evaporates as it is heated, and so water vapor accumulates in the air near large bodies of water, producing relatively humid air. Water vapor is the most potent greenhouse gas in the atmosphere, and this means that the re-radiated microwave energy gets trapped in the atmosphere to a greater degree the more humid the air is.
Now, onto facts regarding the locations of Lund and Binghamton. Lund is close to both the North and Baltic Seas. Prevailing winds everywhere are Westerlies -- flowing west to east. This is caused by the Earth's rotation, with the atmosphere slipping over it as it rotates from the east, creating a general tendency of air movement from west to east. At the same time the Gulf Steam ocean current carries warm water from the tropics across the Atlantic Ocean in the direction of Scandinavia. So, not only is Lund close to large bodies of water, but it lies east of the largest, so air movement generally moves from the North Sea toward Lund. In comparison, the general air movement across Binghamton comes from the dry inland of North America. So the geographical answer here is that Lund is warmer due to its proximity to large bodies of water over which the air flows, carrying humidity toward Lund.
This year in Binghamton, we have experienced an unusually warm winter. One explanation for this could be that global warming has pushed the jet stream that borders regions of warm and cold air further north, as well as increasing its turbulence. This means it is less streamlined and more snake-like, with more brief dips of extreme temperatures, causing unusually warm days in winter.
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