Global borrowing costs are rising as soaring energy prices intensify fears of stagflation, a combination of weak economic growth and high inflation. The yield on Germany's 10-year bonds, the euro area's benchmark, crossed 3.5% on Friday for the first time since April 2011. The European Central Bank raised interest rates on Thursday, while the head of Germany's Bundesbank told CNBC that policymakers may need to move rates into mildly restrictive territory if energy pressures persist.