Climate Change and rainy Midsommars

Hi all,

Back from Sweden and its summer weather: cold and rainy! But I spent Midsummer with a bunch of beautiful, intoxicated people, which made it all so worth it. However, having an international group of people inevitably led to comparisons with weather in other countries: Austria, England, the Netherlands, Germany.. and to people coming to the conclusion that it "didn't use to be like this".

So even though this rainy Midsummer weekend is part of climate variability, not climate change (for an explanation, read this post), there is some truth to the statement that things are changing. So what might this mean for future midsummer festivities? Yep: more rain jackets and scarves, and if we're lucky, sometimes a bikini.

Source: www.thelocal.se

As mentioned before, climate change will mainly manifest itself through the earth's hydro-ecological system, which includes changes in precipitation. Each type of climate will respond differently, based on its characteristics and geographic location. Geographic location influences not only solar irradiation, but also the effect ocean- and wind global circulations have. Swedish climate is generally temperate, with three official climate distinctions in the different parts. From South to North: oceanic, humid continental and subarctic. Because of the warming impact of the Gulf Stream on Sweden, its climate is much milder than other locations around the same latitude. Because of this important influence, large circulation variability because of climate change is likely to have significant effect on Swedish climate and weather (Busuioc et al., 2001).

Depending on the use of climate model, sea level pressure variability will have a moderate to severe effect. As researched by e.g. Busuioc et al. using HadCM2, and Bergström et al., (2001) using several General Circulation Models within the project SWECLIM, the definitive simulated effects depend on optimal statistical downscaling and vary with which model is used. Here are some general conclusions though:

• For all seasons, there is a correlation between sea level pressure and precipitation
• Especially summer and autumn precipitation will increase
• HadCM2 and ECHAM4 respectively predict a 4.5% and 6.9% increase in annual precipitation.
• The North and Middle of Sweden will get wetter, the South will locally get dryer
• Weather will become more extreme, meaning more highs and lows in especially summer

So what can we gather from this? There is a lot more research going on about this topic, but the general consensus is for Sweden that weather will become more wet, with some extreme outliers of increased temperature and solar irradiation. 

So about Midsummer: be prepared to celebrate in the rain, especially north of Stockholm. We might also get lucky some years, and be swimming and tanning while enjoying this wonderful, crazy celebration. But really, who cares: it's always good in its own way. Glad Midsommar, see you next year!