Global Bond Markets Face Worst Month in Years as Energy Shock and AI Boom Push Yields Higher

The world’s biggest sovereign bond markets are heading toward their most difficult month in years as surging energy costs reinforce inflation concerns and the artificial intelligence investment boom supports economic growth, strengthening expectations that interest rates will remain elevated for longer.

The sharp repricing is being felt across the United States, Europe, Britain, Australia and Japan, with investors reassessing the prospect of a prolonged period of higher borrowing costs.

Two-year U.S. Treasury yields have climbed almost 60 basis points in September and are on course for their largest monthly increase since early 2023. Two-year yields in France, Germany, Britain and Australia are also headed for their biggest monthly increases since March, when the Iran war triggered a fresh energy shock.

Japanese government bond yields, meanwhile, remain close to multi-decade highs.

“There’s a realization that the whole energy story and inflation story will not go away in the very short term,” said Kenneth Broux, Societe Generale’s head of corporate research for FX and rates. “Bond markets are adjusting to that.”

The shift has raised alarm because government bonds sit at the foundation of global borrowing costs. Rising sovereign yields feed into mortgage rates, corporate financing, consumer credit and the cost of funding government deficits.

The latest move is seen not as a deterioration in bond prices, but as a representation of a broader reassessment of how quickly interest rates can return to the low levels that prevailed through much of the post-financial-crisis period.

The bond market’s current turmoil differs from the selloff of 2022, when rising inflation and aggressive central-bank tightening produced the worst annual returns on record for global bonds. This time, investors are increasingly focused on the absolute level of borrowing costs as well as the speed at which yields are rising.

The yield on the benchmark 10-year U.S. Treasury has moved above 5% for the first time since 2007 and is heading for its largest monthly increase since 2022, with the September rise approaching 50 basis points.

The repricing has also pushed up household borrowing costs. Data last week showed that the interest rate on the most popular U.S. home loan had risen to its highest level in more than two years. Bond-market volatility has risen accordingly. The ICE BofA MOVE Index, a widely watched gauge of Treasury-market volatility, has jumped almost 30% this month, its largest monthly increase since March.

For investors who have spent years relying on government bonds as a source of portfolio stability, the combination of higher yields and elevated volatility presents a difficult adjustment.

Yet higher yields are also beginning to attract buyers.

Florian Ielpo, head of macro and multi-asset portfolio management at Lombard Odier Investment Managers, said he had become more positive on government bonds because yields have reached levels that offer greater income potential.

The argument is that while bond prices have suffered as yields have climbed, investors buying at higher yields have a larger income cushion if rates eventually stabilize or decline.

The problem is determining when that stabilization will occur.

AI Is Adding to The Competition for Capital

One unusual feature of the current bond-market environment is the role being played by the AI investment boom. Technology companies are borrowing heavily to finance data centers, computing infrastructure and other investments required to expand AI capacity. Bond issuance from hyperscalers has more than doubled this year to above $200 billion, according to LSEG data.

That means additional competition for investors’ capital at a time when governments are already issuing large quantities of debt.

The result is a potential feedback loop. Strong AI investment supports economic growth, which can make it harder for central banks to justify rapid rate cuts. At the same time, the companies financing that investment are issuing more debt, increasing the supply of bonds competing for investor demand.

Ielpo expects government borrowing costs to remain elevated partly because of that competition. The implication is that AI is affecting bond markets through more than its impact on technology stocks. The infrastructure buildout is becoming a significant source of corporate borrowing demand, potentially reinforcing pressure on yields even as governments seek to finance large fiscal deficits.

For companies and private-equity investors, however, current borrowing costs are not necessarily prohibitive.

“5% is not so high by historical standards,” Warburg Pincus CEO Jeffrey Perlman said at a conference in Singapore on Tuesday. “Deals can work at a 5% 10-year.”

That suggests higher rates could eventually become a new normal for corporate finance rather than an immediate barrier to investment, although businesses with weaker cash flows or higher leverage face greater pressure.

Fiscal Risks Add Another Layer

The outlook becomes more complicated in Europe, where fiscal policy is increasingly influencing bond-market pricing.

France’s 10-year government bond yield has risen more than 50 basis points this month, its biggest monthly increase since 2022. The spread over German Bunds has widened to its largest level since 2012 as investors focus on political uncertainty and the country’s budget negotiations.

“Now you have the additional idiosyncratic risks in France’s case, now people think, where’s the budget or there won’t be a budget, what’s going to happen?” said Andrzej Szczepaniak, senior European economist at Nomura.

He also pointed to the rising popularity in opinion polls of far-left presidential contender Jean-Luc Mélenchon as another political factor being watched by markets.

Britain faces its own fiscal test with the country’s upcoming budget under Finance Minister John Healey, while October will also bring fresh U.S. employment and inflation data.

Those releases could determine whether markets continue to price a prolonged period of restrictive monetary policy or begin to anticipate eventual relief.

In the United States, uncertainty is coming from both monetary and fiscal policy.

The September rate increase has reinforced the Federal Reserve’s focus on inflation, but investors remain uncertain about the path of future policy. At the same time, Treasury efforts to manage borrowing costs have created another variable for markets already dealing with heavy government issuance.

“Policy uncertainty is coming at us from two places, the Fed and the Treasury, and I am deeply uncomfortable about the US policy mix,” said Arun Sai, senior multi-asset strategist at Pictet Asset Management.

The coming weeks will therefore test whether the September bond selloff represents a temporary repricing or the beginning of a longer adjustment toward structurally higher interest rates.

For bond investors, higher yields have improved the potential income available from government debt. But for governments, households and companies, the adjustment is considerably more consequential. This is because a sustained 5% Treasury yield changes the cost of financing across the economy and raises the hurdle rate for investments ranging from mortgages to AI data centers.