A record warm May in northern Europe

It’s been an unusual spring in Europe – late in coming, then warm and thundery.

Even before the last day of May when figures were provided, many northern nations were able to announce new temperature records.

Sweden showed a spectacular departure from the norm: every part of the country seems to have been at least 2 degrees Celsius warmer than the 1961-1990 average. The 30-year period to determine an average is the usual standard and suggests significant warming in Sweden, compared with the latter half of the last century.

Maybe more surprising is the difference between May 2018 and any other May on record.

In a series of records producing an average, there will be a “warmest” and “coldest” month. Uppsala exceeded the standing record for warmest May by 1.4C in a series that started in 1739. Stockholm beat a 261-year record by nearly 2C. To see such a difference to a record in a long-lived line of statistics is significant.

If Sweden had been alone, there might have been a random local reason, but many other countries reported a similarly warm May.

Latvia lists an average May temperature of 11.3C and a record of 14.4C. May 2018 set down a new figure of 15.2C. Belgium beat the 2008 May average by 0.5C at a surprising 21.8C

Denmark is still finalising figures that already suggest the warmest and sunniest May on record. The long-term average for Denmark is 11.3C. The year 1889 was the warmest May on record at 13.8C, but 2018 looks to beat that figure by 1 degree C. Again, this is statistically significant.

Some weather scientists have suggested this warming trend is being caused by climate change. After another winter where ice failed to cover the Arctic Sea, the weather has been profoundly different from expectations for months.

For much of May, the weather pattern of Europe has stayed the same, enabling a continual feed of warm winds into eastern and northern Europe. This provided blue skies, allowing the strengthening sunshine to warm to its maximum capability.