Agence France-Presse: United States President Barack Obama promised on Sunday to take the lead in global efforts to tackle climate change, which Europe has long accused Washington of failing to address seriously. “To protect our planet, now is the time to change the way that we use energy,” he told a crowd gathered at Prague Castle for his only public speech during his maiden tour of Europe. “Together we must confront climate change by ending the world’s dependency on fossil fuels by tapping the …