Sweden has a relatively cold climate, so it may seem unnecessary to have a warning system for heat. However, research in recent years has shown that it is highly relevant even for Sweden. A system is now being prepared that will provide advance warning of hot periods and excessive levels of air pollutants which often arise in connection with a heat wave.
“This is important because it’s about people’s health,” says Joakim Langner, project leader at SMHI. “We know that heat waves cause increased mortality also in Sweden, especially among at-risk groups and the elderly. But just how hot is too hot? And how long should a heat wave last to warrant issuing a warning? Should we only issue a warning for excessive temperatures, or also for the combination of air pollutants that is elevated during a heat wave?”
When does heat become health threatening?
In collaboration with the Occupational and Environmental Medicine unit at Umeå University, appropriate warning criteria are being developed, tailored to the Swedish population.
“Researchers at Umeå University are helping us set relevant criteria for how heat affects human health,” Joakim explains. “We’re looking at the relationship between different weather parameters and increased mortality. The analysis includes both temperature and air humidity.”
Climate change brings higher temperatures in Sweden
There is a long-term risk of higher temperatures in Sweden, linked to a change in climate. Swedes are generally less accustomed, and therefore more sensitive, to high temperatures than Southern Europeans for instance.
In high-pressure situations during the summer, higher levels of air pollutants which also increase health risks occur, such as ground level ozone. Particularly on the continent this is a common problem in connection with high temperatures and strong insolation. In a heat wave, raised levels of ground level ozone can be transported to Sweden.
“Higher temperatures also entail a greater risk of grass and forest wild fires. Fires are of course primarily a local problem, but air pollution from major fires in our proximity can travel to Sweden, and episodically produce elevated levels of particles and other air pollutants,” Joakim explains.
Defining the right warning criteria
A national warning system for heat waves can effectively help improve society’s preparedness and preventive measures in the event of a heat wave. Within the framework of a special government subsidy for emergency planning, SMHI is developing a warning system in co-operation with relevant authorities. Ultimately, various care providers and the general public will be able to use the warnings to make preparations and take action. The ambition is for a warning system to be operational by summer 2013.