Climate change may increase the risk of severe thunderstorms

Climate model simulations suggest that on average, as the surface temperature and moisture increases the conditions for thunderstorms becomes more frequent. Climate change decreases temperature difference between the poles and the equator. This leads to a decrease in vertical wind shear, which is a major factor determining what type of severe weather occurs. These expectations are supported by a majority of the climate model simulations that have looked at the variables.

However risks of tornadoes and hail are still open to many questions. The small scale of severe thunderstorms makes it difficult to deal with them with global models. The estimations of their occurrence in the future climate is based on the occurrence of their favorable environments in climate model simulations.

"According to latest research the intensity of tornadoes will not increase, therefore incidents like in Oklahoma are not expected to be more frequent than today," said Harold Brooks, who is one of the most well-known researchers of severe thunderstorms from National Severe Storms Laboratory, USA.

"Most of the research on severe thunderstorms and tornadoes in climate change has focused on the USA and it is unclear how well the lessons learned there apply to the rest of the world," Brooks concluded.

Thunderstorms cause the most severe damage in Finland

Most severe weather incidents in Finland are caused by phenomena related to thunderstorms such as lightning, strong wind gusts, hail and tornadoes. On average one person is killed every second year because of a lightning strike. Thunderstorms can cause also severe damage to the property because of falling trees and strong winds. On average, about 14 cases of tornadoes are reported in Finland annually. Most of them are quite weak but also some significant cases have been reported in history.

"As climate models are being developed, we are beginning to get more accurate information about the impacts of climate change to severe weather incidents in areas like Finland," says meteorologist Pauli Jokinen from Finnish Meteorological Institute.