Europe will have to rely on higher wind speeds this autumn to see a rise in annual clean power generation as electricity output from wind slumped earlier this year and solar passed its yearly peak in the summer. Europe’s electricity supply from wind fell by 6% in January to August from a year earlier, according to estimates by think tank Ember cited by Reuters columnist Gavin Maguire. Total clean electricity supply in Europe fell by 2% in the first eight months of the year compared to the same period of last year,…