In the years 1998-2013, Eurasia experienced very cold winters, despite the ongoing global warming trend. Scientists are debating their origin, but we have come closer to finding out.

A study led by Lingling Suo (researcher at the Nansen Center) has an answer. An ocean phenomenon might be contributing to the cold winters. The investigated phenomenon in the Pacific Ocean is the “Interdecadal Pacific Oscillation”. It can occur as two different types, and each of them can last up to 15-30 years at a time.

The first type has warmer water temperatures in the tropical regions and colder ones in the northern regions. The second type is the exact opposite: cooler water temperatures in the tropics and warmer ones in the North. The water temperatures can also be close to average, in transition between the types.

They show that the phenomenon impacts the winter air temperatures in western Eurasia. When being expressed as cooler water temperatures in the South and warmer ones in the North, extremely cold winters are likely. In the period between 1998-2013, they showed that it causes much of the western Eurasian winter cooling. They also conclude that the phenomenon’s other type likely reduces cold winter temperatures. We are currently seeing the second type of the phenomenon at work again, making severely cold winters in western Eurasia more likely than warmer winters. With the water temperatures in the Pacific Ocean varying in the future, the intensity of the coming winters in western Eurasia will likely depend on those changes.