16.01.2013 15:23

Need a climate forecast for the next 130, 10,000 or 120,000 years?

In 10,000 years' time, the coastline of western Finland will have moved 20 kilometres to the west, the climate will favour broadleaf trees, and the nesting season for birds will be longer than now. Although nobody can know for sure what sort of climate will prevail in Olkiluoto in thousands of years from now, forecasts are necessary when planning the final disposal of spent nuclear fuel.

Anne Lehtinen, hydrogeologist from Posiva, what can be said about the changes that will take place in the Olkiluoto climate within the next 10,000 years?

"Modelling shows that the climate will warm during the next few thousand years. Usually, this also means increased rainfall. The climate type is assumed to remain temperate, much like it is now.

It is likely that vegetation zones will move to the north. Plants that currently grow at the level of Denmark could then be found in Finland. Conifers will yield to broadleaf trees, and the nesting season for birds will be longer."

How much could the climate warm according to estimates?

"Simulations analysed by the Finnish Meteorological Institute show a global temperature increase of 0.3–8 degrees Celcius within the current millennium. The temperature increase is mainly due to greenhouse gas emissions resulting from human activities. Ultimately, the actual increase will depend on the amount of emissions we produce."

Why does Posiva need to have climate forecasts that reach far into the future?

"The climate models created by the Finnish Meteorological Institute concern the long-term safety of the final disposal of nuclear materials. Posiva has coordinated the modelling projects. Climate modelling is a part of the surveys carried out to assess the suitability of Olkiluoto as a final disposal site."

Anne Lehtinen
Anne Lehtinen is working as hydrogeologist in Posiva Oy at Olkiluoto

Will Posiva need other similar estimates in addition to the climate models?

"The rise of the sea level has also been estimated as a part of the future scenarios reaching into 10,000 years from now. However, these estimates involve great uncertainties.

According to the estimates, the average level of the Baltic Sea may rise 0.3–8 metres within the next few thousand years. At the same time, however, land uplift resulting from the last ice age is still in progress. It has been estimated that during the next 1,500 years, the rise in the sea level may exceed the uplift rate, but after that, the uplift is likely to be faster than the rise of the sea level.

In any case, we must look for answers to questions such as whether the sea level will reach the entrance to the underground research facility ONKALO."

Has the development of the climate been estimated for periods of time shorter than 10,000 years?

"On assignment for Posiva, the Finnish Meteorological Institute has assessed extreme weather phenomena that may occur in the Olkiluoto area during the next 130 years. Based on the results, the Finnish climate will warm in the current century, and rainfall will increase. As the climate warms, extreme temperatures are believed to become stronger; for example, heat waves will be hotter than now. Heavy rainfall is also likely to become more common.

When such time spans are involved, estimates are based more on forecasting than modelling. Certain cycles have been repeated in weather phenomena, and will continue to be repeated in the near future."

How far into the future do climate models reach?

"Posiva's long-term safety assessments include the Finnish Meteorological Institute's climate scenarios that reach up to 120,000 years into the future. This is such an extensive time scale that the models involve a lot of uncertainties, but rough estimates of potential climate developments have nevertheless been considered important. Modelling included a simulation of events 100,000 years back in time, which helped increase the reliability of the forecasts."

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