Global government bonds sell off as borrowing costs hit multi-decade highs

Government bonds sold off globally on Wednesday, extending a rout that has driven borrowing costs to multi-decade highs.

The yield on German 10-year bunds , the benchmark for the euro area, was 4 basis points higher at 3.375% on Wednesday morning — its highest level since 2011. Japan's 10-year yield stood at 3.016%, after crossing 3% for the first time in three decades on Tuesday.

The 10-year Treasury yield remained above 4.8%, a level last topped in early 2025, as British 10-year gilts extended their post-2008 high to 5.25%.

Yields move in the opposite direction to prices.

Investors have been rattled by the resurgence of inflationary pressures, particularly as a fresh wave of conflict in the Middle East drives oil prices higher. That has added to longstanding concerns about the fiscal positions and high debt loads of major economies from the U.S. to Japan and France.

Central banks around the world are meanwhile seen preparing for a string of interest rate hikes this month, typically bad news for bonds. Federal Reserve Chair Kevin Warsh struck a hawkish tone in his closely watched speech in Jackson Hole last week, while the Bank of Japan is seen potentially raising rates to support a falling yen, and markets are fully pricing a rate hike by the European Central Bank following the release of EU inflation data on Tuesday.

Equity markets have also entered risk-off mode, with the major U.S. indices falling for three straight sessions and European and Asian markets also in the red. That follows strong gains this year, with many stock markets at record highs as enthusiasm around the AI boom continues, despite the volatile geopolitical backdrop.

"The fundamental tenets [in markets] are a little shakier than they've been," George Maris, chief investment officer and global head of equities at Principal Asset Management, told CNBC's "Squawk Box Europe" on Wednesday.

"And if the cost of money, the cost of risk rises, that's what you're seeing with the global rise in yields everywhere."

"You look at debt levels around the world that are at stratospheric levels and increasing. The solutions for curing that do not seem readily apparent ... I don't see the political willingness to tackle this anywhere. I think that's a problem," Maris added.

"I think the fact that this is all happening in a period of healthy global economic growth, that you're seeing the debt levels pick up, means that we're in a more precarious place for if there's disturbance."