Key borrowing rate shoots to 6-month high as traders ditch government bonds around the world

A key borrowing rate shot to a five-month high Tuesday morning, as traders around the world continued to sell off big government bonds.

The drop in price for the 10-year Treasury drove its yield up to 2.35 percent early Tuesday, the highest level since late November.

The recent rout started last month in Europe, according to bond traders, and has since spilled into U.S. markets. Worried about the strength of the global economy, nervous investors had crowded into government bond markets in Germany and the U.S., pushing prices up and yields down.

In the middle of April, the 10-year German yield reached as low to 0.07 percent, while the 10-year U.S. Treasury sank to 1.86 percent. Investors were essentially buying safety.

What happened next has left many in the markets scratching their heads. Plenty of traders decided they owned too many German government bonds and decided to sell. The shift came so fast that it forced banks to raise cash through selling Treasury bonds, traders said. And that, in turn, helped send U.S. long-term interest rates up.

What's it mean to most Americans? Incredibly cheap mortgages aren't quite as cheap. The 10-year rate acts like an anchor for borrowing costs throughout the economy, and its plunge in recent years sliced mortgage rates nearly in half, knocking them to the lowest levels since long-term mortgages started in the 1950s.

In November 2012, the 30-year mortgage rate hit a record low of 3.31 percent. A decade ago, the average rate was 5.9 percent.

The bond market's recent drop has turned that trend in the opposite direction, nudging mortgage rates up. Over the past three months, the average 30-year mortgage has climbed from 3.59 percent to 3.80 percent, according to Freddie Mac. That's an additional $12 a month for every $100,000 in mortgage debt.