CC3 Average temperature

>> Background information

Development

Interpreted as a linear change, the average temperature of Finland has risen by approximately one degree during the past hundred years. However, if the past 100 years is analysed by looking at a ten year moving average then the average temperature has risen from slightly over one degree to almost three, that is nearly by two degrees in total.

The exceptionally warm period during the 1930s can be seen as a clear peak in the graphs. This sudden warming, which was probably due to shifting sea currents, was most pronounced in the northern parts of the northern hemisphere. However, the warm period quickly subsided and the average temperature mostly fell thereafter until the early 1990s. During the 90s the trend turned clearly upwards again. The first decade of the 21st century was already warmer than the 1930s on average.

Looking at the change in average temperatures along a south to north axis reveals no great differences. The warming seems to have been slightly greater in the observation stations of southern Finland. However, the time series of individual stations must be interpreted cautiously due to natural varialibility and the impact of urbanisation, for example.

Impact on biodiversity

Although being a very crude measure in relation to biodiversity, average temperature nevertheless shows the main direction and overall scale of change in climate clearly. When the average temperature rises winters become shorter and the period when plants are able to photosynthesize becomes longer, for example. This enables many southern species to spread into Finland. It may also drive northern species out of the country due to increasing competition, for instance.

The effects of the 1?2 degrees rise that has been observed in Finland can already be seen in several ways in the occurence of species. Numerous new butterfly and bird species have been recorded in Finland. As mobile species these are able to react to rising temperatures shiftly. In northern Finland, the treeline has started to move upwards along the sides of fells and the special northern mire habitats, palsa mires, have begun to melt.

Many other indicators represent more accurately the climatic factors affecting the lives and life histories of individual organisms. Examples of such indicators include the start and end as well as the lenght of growing season and the duration of snow and ice cover. In addition to phenomena that may be reduced to annual averages many random events such as heavy rains, dry periods and low temparatures have a great impact of individuals and even whole species.