The polar vortex, which has brought severe disruption and record low temperatures to the US in recent weeks, has gone on to warm areas of Scandinavia, confusing the seasonal patterns of flora and fauna.
The vortex is a weather pattern made up of strong winds circulating around a low-pressure system. It broke away from its normal winter position over the Arctic because of a weakening of the jet stream – a belt of fast westerly winds that normally act as a boundary between cold northern air and warmer southern air.
The vortex caused plummeting temperatures during its visit to the US, where temperatures reached lows of -37C. However, in Nordic countries it has had a very different effect.
While cold air was allowed to spill into the US and Canada, more humid temperatures have come to much of Europe.
Following on from an already warmer than average winter, this has led to increased rainfall in countries including Norway and Finland.
This in turn has reportedly caused hibernating bears to wake up early in Finland, while plants such as daffodils have emerged as early as December 14 in Norway.
WWF Norway chief executive Nina Jensen said she was “cautious about drawing conclusions from one mild winter into specific changes in nature”, but observed that some changes were happening.
“We are definitely seeing plants like bluebells flowering that wouldn’t come out until spring, and birds singing that wouldn’t normally be at this time of year. There are quite obvious changes in the growth season, plant growth and migratory bird routes and timing”, she said.
“The flip side of this warmer winter is that we will also have an increasing threat of harmful introduced organisms, such as the wild boar or ticks that thrive in warmer temperatures.”
Scientists have suggested that the weakening in the jet stream that has made the polar vortex’s abnormal travels possible has been caused by climate change.
In the US, some commentators attempted to claim that the record-breaking cold disproved global warming.
Satirist Jon Stewart, host of the The Daily Show on Comedy Central, responded, “Global warming: just one more liberal conspiracy, because even though there is a great deal of scientific data establishing climate change and even though many of the models for global warming predict more extremes of weather – not just warming – apparently decades of peer-reviewed scientific study can be – like a ficus plant – destroyed in one cold weekend.”