New climate projections indicate more extreme weather

Extreme weather will be more common in Europe, heavy rain and heat waves will be more frequent and more intense than at present. New climate projections for severe weather situations in 100 years also show that truly cold days will virtually disappear.

New projections for extreme weather situations in Europe in the future have been produced by Rossby Centre, SMHI’s climate research unit. The new scenarios show the effects of global warming with more details than before, thanks to more computer power and high geographical resolution.

“By using more models, or ensembles, we can study the spread of the results and thereby illustrate uncertainty in the future scenarios. We see similar changes in extreme temperatures among the simulations, but there are no clear signals for wind,” says Grigory Nikulin, a climate scientist at SMHI.

More extreme heat and rain

The results for temperature show that the extreme events that have so far occurred once every 20 years on average could occur every year in Southern Europe and every three to five years in Scandinavia. So for instance, the scenarios indicate that a location in southern Sweden that now experiences temperatures of 35°C once every 20 years, may experience such temperatures every four years in the future, on average. Temperatures of 40°C could occur every 20 years in these places.

Truly cold weather, such as -10°C in Spain or -30°C in southern Sweden, is unlikely to occur in future.

When it comes to precipitation, previous climate scenarios have shown that total precipitation will decrease in the long term in some regions such as Southern Europe. However, the pattern for extreme precipitation will differ in many of these places, with increased frequency and intensity. Extreme precipitation that has previously occurred once every 20 years could occur every eight years in Scandinavia, and even as often as every three years during winter in some places.

According to the scenarios, the amount of extreme rainfall could rise by up to 40% in Scandinavia and North-Eastern Europe. Intense rainfall of 20 mm/day today would correspond to 28 mm/day in the future.

More development for extreme wind

The projections for precipitation have a larger spread in their results than for temperatures. However, there is a common tendency for the extremes to grow in frequency and intensity.

There are currently no reliable data regarding extreme wind conditions in the future, even though some simulations suggest that strong winds could increase in the Baltic Sea. A far-reaching project is under way to map which processes are the most important for understanding development of the winds.

Grigory Nikulin, climate researcher.

“As a whole, the new ensembles are an important foundation for continued climate research. However, they can already be applied to many areas,” says Grigory Nikulin.

The term extreme weather means there is little likelihood they will occur, although the limits vary depending on factors such as geography, topography and the sensitivity of different sectors. An established method for defining extreme values has been used in the projections, known as the extreme value theory.

The new ensembles for extreme weather comprise results from a high-resolution regional climate model with input data from six different global models, with an emission scenario (A1B - see IPCC report).

The report on extreme weather (see link on right) will also be published in Tellus magazine.
Read more about natural variability of the climate in Rossby Centre NewsletterMay 09,  "Understanding the time-axis in coupled climate models: Uncertainty, natural variability and the need for an ensemble approach".