https://phys.org/news/2018-05-years-high-danube-temperatures-climate.html

A German-Romanian research team has sought to determine why. "When climate researchers talk about ice and global warming, most people think of the Greenland Ice Sheet or the sea ice on the Arctic Ocean. Most of them don't realise that the amount of winter ice on Europe's seas and rivers is an equally important indicator for a changing climate," explains Dr. Monica Ionita, a climate researcher at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

She and her colleagues have compared the ice records from Tulcea and other cities along the Danube with local and national meteorological time series. Their findings show that the climate in Central and Eastern Europe has changed substantially over the past several decades. "In Europe, there has been a clearly recognisable rise in winter temperatures since the late 1940s. Ever since then, the winter months have rarely been sufficiently cold, and the Danube and other major rivers can no longer freeze over on a regular or extended basis," says Monica Ionita.