Cold comfort farming: German ice wine maker hails crucial big chill

You might get one chance in a decade,' says Ralf Petgen, who has adapted his Mosel vineyard owing to global heating

On a recent frosty night, Ralf Petgen made use of the light of a full moon to check every hour on the state of his riesling grapes. The weather forecast over the two previous days had given the winemaker hope that for the first time in years he would fulfil his dream of harvesting his grapes in a frozen state and turn them into Eiswein.

The temperature needs to be -7C, no warmer than that," he said. And we hadn't had it as low as that while the grapes were still in a healthy state, since 2012."