Finnish climate is expected to change more during winter than during summer months

Global warming caused by an intensifying greenhouse effect will not affect Finland in the same way all year round. The impacts felt in Finland are also expected to be different than in such areas as Southern Europe.

Winters will become significantly warmer and there will be more rain during the winter months, while the changes in the summer will be less marked.

When compared with the summers of the past few decades, this summer has been fairly chilly in Finland but a century ago such temperatures would have been quite common. Warm weather has not, however, disappeared from the earth this year: Warm air currents have travelled to such areas as southern parts of Europe where temperatures of more than 40 degrees have been recorded this summer.

Global warming is expected to make Finnish summers warmer. On average, summers are expected to become about 0.3 degrees warmer each decade during the first half of this century. The rate of change during the later decades depends on the growth of greenhouse gas emissions. Even a slight increase in temperatures will have an impact on the occurrence of very high temperatures. As global warming is progressing, high extreme temperatures are becoming increasingly likely, while at the same time low extremes are become less common. For example, the year 2015 was the warmest ever recorded in Southern Finland. Few people would believe this because, as in this summer, there were few spells of hot weather two years ago. In fact, the record-high average for 2015 was caused by an extremely mild autumn and winter. "This is one of the unpleasant scenarios of global warming: Mild winters with little snow and a lot of darkness are becoming increasingly common in southern and central parts of Finland", explains Juhani Damski, Director-General of the Finnish Meteorological Institute. Summers will also become warmer but more slowly than winters.

Since the mid-19th century, the average temperature in Finland has already risen by more than two degrees. The average rate of increase during the period has been 0.14 degrees each decade, which is almost twice the global average. The rise in average temperatures is already having an impact on Finnish weather and nature. It should be remembered, however, that even though the climate is changing, the annual variation will remain. This means that there will still be years that are colder than average and years that are warmer than average.

Based on the results of the climate change models, there is a more than 95 per cent likelihood that in the next decade, the average temperatures in Finland will be higher than during the reference period 1971 - 2000. If the efforts to limit greenhouse gas emissions are reasonably successful (RCP4.5 scenario), the annual average temperatures in Finland are expected to rise by 2-5 degrees by the end of the century, from the levels of the late 20th century. In this scenario, winters would be 2-7 degrees and summers 1-4 degrees warmer. If the actual rise in temperatures is halfway between these two uncertainty figures, the areas around the Arctic Circle will, by the end of century, have the same climate as Southern Finland has now.

Cold winters are becoming less common

In the short run, winter temperatures are likely to rise more rapidly than summer temperatures even though there is also a great deal of variation in winter temperatures in particular. As climate change progresses, cold winters are becoming less common. As average temperatures are increasing, there will be fewer days with sub-zero temperatures and the thermal growing season will become longer. There will be less fluctuation in winter temperatures and as a result, the lowest extremes will rise more than the average temperatures. Winters will become cloudier and the average snow cover will decline.

Heavy rainfall will become more common during the summer months in Finland

As the greenhouse effect is intensifying, it will impact precipitation in addition to what takes place as a result of natural climatic variation much more slowly than changes in temperatures. Both the rise in temperatures and the increase in precipitation are more marked in winter than in summer. The results indicate that there will be an increasing number of rainy days and more rainfall in winter, while the longest dry periods will become shorter. Heavy rainfall will also become more common during the summer months.

Summers in Europe, especially in the Mediterranean countries, will become warmer and drier. The results of modelling indicate that the heat waves resembling those experienced this summer will also become more common in Central Europe. Climate change is thus expected to make extremely high temperatures more intense and more widespread.

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Published: 23.8.2017
Categories: Research

Original press release