Warm Arctic Cold Europe
Recent cold winters in both Europe and North America have led to some claiming that global warming is a ‘hoax’. The argument is logical, with a warmer world we would expect to see warmer temperatures, however the relationship isn’t so simple. There is natural climate variability to consider, whilst we may be lessening the chance of cold winters, they are still possible. One hypothesis being hotly debated at the moment is that warmer temperatures in the Arctic could be a factor in colder Eurasian winters. The current warming trend has been far more pronounced in the Arctic, melting large swathes of sea ice which in turn accelerate warming. Several studies including Tang et al (2014) and Liu et al (2014) have linked these Arctic temperature ‘amplification’ to cold surface temperatures in the mid-latitudes.
Recent modeling by Mori et al (2014) has suggested that as the Arctic warms, the warmer waters of the Atlantic Jet stream are able to push further north. This can be caused by sea-level pressure variation known as the Arctic oscillation, however the authors argue that it’s lack of persistence since 2004/5 cannot explain the temperature trend. Instead they argue for a new pattern they imaginatively call Warm Arctic Cold Eurasia (WACE) since 2004. This causes a difference in pressure between the Arctic and Mid-latitudes drawing polar winds southward and amplifying cold winter temperatures.
The jury is still out, with other authors, such as Peings & Magnusdottir (2014), suggesting that a resurgence in cold weather is part of the Atlantic Multidecadal Oscillation, which is heavily influenced by the Arctic sea. Whilst Screen (2014) argues that winter temperatures have actually seen a greater warming trend than summer.
Much like the debate over recent Antarctic sea ice extent many hypothesis are currently being examined over the relationship between Arctic and mid-latitude weather. Ocean and atmospheric circulation are highly variable and that is likely to complicate further as the world continues to warm.