Temperatures are rising faster than ever. According to climate models the temperature rise may be between three and six degrees by the end of this century. The warming effect in northern areas will be 50 percent greater than the global average.

”The global average temperature has risen approximately 0.7 degrees in a hundred years, while the corresponding value in Finland is more than one degree,” says Professor Ari Laaksonen from the Finnish Meteorological Institute.

According to Laaksonen, from the point of view of predictions, the development of emissions will not make much difference until the year 2040. Different scenarios still provide fairly similar results about the rising global temperature. The rise is expected to be roughly one degree. ”This is mostly due to the large ocean heat capacity. Oceans work as a slowing buffer both ways,” Laaksonen explains.

Predictions that have been created for the period beyond 2040 depend on how well we succeed in limiting greenhouse gas emissions. In the most optimistic assessment the global warming will remain at three degrees by the end of the century, but in the most pessimistic prediction the rise is almost six degrees.

The optimistic alternative sets a precondition that the greenhouse emissions will be promptly reduced, and the pessimistic value represents the situation of doing nothing, a scenario, with the emissions continuing to rise as they do today.

When the plans change – welcome to Central Europe

If the last-mentioned alternative is realized, the climate in Finland will resemble the climate in the Central Europe of today. Along with the rising temperature, precipitation will increase by approximately 20 percent. Since both temperatures and rainfall are estimated to increase the most during winters, the winter temperature in Finland might rise 7–8 degrees and rainfall could increase as much as 30 percent.

Such rapid changes will be hard for nature to cope with. Laaksonen also points out that even if  temperature-wise Finland were close to Central Europe, with regard to the amount of light the situation will remain as it is today.

With rises in temperature and rainfall increases, forest nature would go through radical changes throughout Finland. The northern conifer zone would transfer hundreds of kilometers towards the north, and in the most southern Finland the growth of spruce, for example, would decline to less than one fifth of today's figures. In contrast, broadleaved trees would become common throughout Finland. When dry periods become more common, it increases the risk of forest fires. When the frostless period becomes longer, it may mean heavier damage due to storms.

Along with increasing winter temperatures pathogens and pests may become serious problems in Finland. Most plant pathogens and viruses are spread by insects and warmer weather improves the overwintering capabilities of many insects. Furthermore, the communication of pathogens from animal to human hosts may become more common.

According to the most recent studies the sea level may rise as much as one meter by the end of the century. If this scenario will be realized, we should be prepared for a corresponding rise also at the Baltic Sea. This would particularly affect the coastal areas of the Finnish Gulf in the form of more severe coastal floods.

However, it is likely that Finland will cope with the changes better than many other areas, and locally effects may even be positive. At the global scale, however, damages will be much worse than benefits.For instance, the living conditions in the developing countries may deteriorate so much that vast areas will become unfit for living. This will inevitably affect also the neighboring areas. But how? The climate models cannot answer this question.

History into perspective

The basis for all climate research is to understand the laws of nature. The variation and changes that have already taken place help to test this understanding. Temperatures have been consistently measured only since the 1850s, so data before that is based on indirect observations. Against this information we can test how well the current climate models work.

”Temperatures that prevailed in the past can be determined, for example, from annual rings of trees and sediment layers in lakes. However, there is always uncertainty involved with observations. Hence, it is interesting to investigate what climate models tell us about the corresponding time,” Ari Laaksonen reflects.

The development of climate modeling has been dynamic in Finland, but longer simulations have become possible only quite recently. Currently the Finnish Meteorological Institute participates in a climate simulation project directed by the Max Planck Institute.

The simulation covers a thousand years and the aim is to study the effects of human activities on the climate of the past. The thousand years contains many scientifically interesting – and controversial – periods, such as the warm Middle Ages and the Little Ice Age.

”Although the increase of greenhouse gas concentrations due to human activities started only with
industrialization, humans have made their mark on the climate even before that. For example, forests were cut
down in Europe to make room for cultivation. After fellings, solar radiation has been more intensive, and this in turn has had a direct impact on the climate,” says Laaksonen.

Volcanos ’ telling

Simulations of a thousand years can also help to explain how nature’s own climate forcing agents, such as variation in solar radiation brightness and volcanic eruptions, have impacted climate. The most recent eruption that produced particles into the stratosphere was the one of Mount Pinatubo in the Philippines in 1991.

Large eruptions are known to have a cooling effect on climate, so the results received from the simulation increased our trust on the model’s reliability. According to Laaksonen, the climate model runs performed after the Pinatubo eruption enabled accurate description of the cooling effect of a half degree over two years.

Interesting results are expected also from the synergy studies of volcanic eruptions and the El Niño and La Niña ocean currents in the Pacific. If, for example, the cooling effect of La Niña is combined with a large eruption, then how strong is the cooling effect in total?

Steps of progress are continuously being taken in climate modeling. This year the Finnish Meteorological Institute has started a modeling run on CSC's supercomputer to analyze a thousand years of especially volcanic eruptions. This is the first study with such a long time span conducted by the Institute on its own.

”A single model run does not necessarily allow very reliable conclusions, but based on several parallel runs it is possible to find out statistically significant issues,” Laaksonen elucidates the meaning of the thousand year simulation.

An important leap in the development has also been the implementation of a regional climate model, which
facilitates making more accurate regional scenarios. At best, a regional model allows us to investigate climate at a grid scale of ten kilometers, while in the global model the scale is at least hundreds of kilometers.

Laaksonen explains that one of the goals for the near future is to use a regional model to determine how
much forest draining, i.e. drying of mires into forests, during the last 100 years has affected the climate in Finland. Supercomputers are essential also in this project.

”Currently CSC is the only body that can provide sufficient capacity for all climate simulations of the Finnish Meteorological Institute, both for regional and global climate modeling,” says Laaksonen.

Adaptation or emergency assistance?

The importance of climate change predictions has increased around the world and they are seen as an increasingly important source of information. Computers can be an essential tool also for the development of adaptation mechanisms and fighting measures against climate change.

Laaksonen finds adaptation to changes to be possible, at least to some extent. One possibility might be ‘geoengineering’ solutions, of which Laaksonen picks as an example coal-fuelled power plants, from which carbon dioxide is returned to the Earth’s crust.

”The function of a volcano can be mimicked, for example, by shooting sulfur dioxide into the stratosphere where it reforms into particles and cools the climate,” he explains.

However, such solutions require great resources. This type of tampering with nature’s cycles inevitably increases the risks involved. For example, in a simulation of a volcanic eruption, particle emissions produced from sulfur dioxide worsen ozone depletion in the stratosphere.

However, the new means are considered worth of studying, especially since models make it possible to test them before a crucial step is taken

Katja Liesilinna