by Niina Heikkinen and ClimateWire, Scientific American, January 5, 2015
In Finland, the rate of warming increased to 0.2 to 0.4 C per decade after the 1960s, providing further proof of the human influence on global warming, according to the Finnish researchers. The increase in average monthly temperature was most noticeable over the months of November, December and January. Temperatures were also warmer than the annual average from March through May.
A temperature series study recently published in the International Journal of Climatology found that over 175 years (1838 to 2012), the annual average temperature in Oslo, Norway, has gone up 1.5 C. The most noticeable changes occurred in the last 50 years and in the early 20th century until the 1930s.
During the summer months, the newly ice-free parts of the ocean take in much more heat than they used to. That heat is then released in the autumn and winter as air temperatures fall. The higher atmospheric temperatures lead to even more ice melt and prevent new ice from forming, creating a feedback loop. Changes in cloud cover and ocean currents also contribute to temperature changes. The Atlantic Multidecadal Oscillation, which causes natural variability in the north Atlantic Ocean, may also be preventing ice from forming in parts of the Arctic, according to Serreze.