Disastrous floods in the Balkans two years ago are likely linked to the temporary slowdown of portions of Earth’s jet stream. Jet Stream patterns circling the globe in the form of large oscillating waves between the Equator and the North Pole, along with shifting ocean currents have caused extreme weather events over Bosnia and Herzegovina, Serbia and Croatia that poured out record amounts of rain.
The study adds evidence that planetary wave resonance is a key mechanism for causing extreme weather event. Further, the scientists showed that extreme rainfall events are strongly increasing in certain geological areas, in this case over the Balkans.
“We were surprised to see how long the weather system that led to this recent flooding stayed over the region,” says Lisa Stadtherr from the Potsdam Institute for Climate Impact Research (PIK), lead-author of the study to be published in Science Advances. “Day after day the rain was soaking the soil until it was saturated, which lead to the flooding that reportedly caused several dozen casualties and 3.5 billion Euro of damages.”
Sunspots → Solar Flares (charged particles) → Magnetic Field Shift → Shifting Ocean and Jet Stream Currents → Extreme Weather and Human Disruption (mitch battros 1998)
While the mean daily rainfall in the Balkans has increased only a little since 1950, the intensity of the strongest rainfall events rose by one third, the scientists found. In May 2014, daily rainfall amounts were locally bigger than ever before in the observed period. The frequency of such potentially devastating extremes in the Balkans, though they are still rare, doubled over the past sixty years.
There was a similar situation in 1977 in Germany, resulting in the “Elbe” flooding. “This is worrisome because we’re seeing increasing extreme rainfall in many parts of the globe,” says co-author and PIK project head Dim Coumou. “The changes over the Balkan are substantially larger than those expected from simple warming of the air.” Regional temperatures rose by one degree since the middle of the past century, and the increased water holding capacity of warmer air intensifies heavy rainfall by about 7 percent per degree of warming. “Yet the observed rainfall changes in the Balkans are roughly five times that much – hence other factors must have come into play.”
This mechanism has first been put forward by PIK scientist Vladimir Petoukhov only a few years ago, opening a new branch of research; he is co-author of the present study. The scientists produced a video to explain the mechanism which might be a decisive factor for creating extreme weather events in summer in general. (actually by Mitch Battros in 1998)
“Our findings provide more evidence that planetary waves cause extreme weather events,” says co-author Stefan Rahmstorf, chair of PIK’s research team. “When such atmospheric waves start to oscillate this can have serious impacts for people on the ground. I am concerned this current climate cycle may be creating conditions more favorable for this kind of fluctuation.”