The outlook for developed economies remained dangerous in November despite an emerging split between Europe, ravaged by an intensifying sovereign debt crisis, and a slightly better performance in the United States.

Reuters polls of more than 250 economists, taken after G20 leaders left a critical summit in Cannes with no concrete plans to solve the crisis, provide some of the strongest evidence yet that the euro zone is already in recession.

With the consensus for that happening at 60 percent, the only wonder is that it is not higher given recent dire economic reports and a prediction by Mario Draghi, the new European Central Bank chief, of a "mild recession" by year-end.

"The euro area economy is decoupling from the rest of the world," said Bruce Kasman, head of economic research at J.P. Morgan, in a note outlining how recent purchasing managers' surveys are "firmly" indicating recession.

In Britain, which relies heavily on Europe for exports, recession odds are now at 40 percent, up from one in three, a consensus probability that has correctly predicted "surprise" Bank of England policy moves in the past.

Recent evidence also shows that when the forecast figure gets that high, subsequent official data proves the economy was already in a slump.

"The outlook for the global economy is very challenging as problems in developed markets begin to affect growth rates around the world," HSBC said on Wednesday as it threatened once again to leave Britain over planned banking regulation.

With yields on benchmark Italian sovereign debt surging on Wednesday to well above 7 percent, a level that is widely deemed as unsustainable, the findings could scarcely come at a more dangerous time for the euro zone.

While some economists like Kasman remain more optimistic on the United States as well as emerging economies, the head of the International Monetary Fund on Wednesday warned of the risk of a "lost decade" for the global economy.

"There are clearly clouds on the horizon. Clouds on the horizon particularly in the advanced economies and particularly so in the European Union and the United States," said IMF Managing Director Christine Lagarde.

Recent U.S. economic data have come in slightly better than expected, particularly on output. But growth is not fast enough to reduce unemployment in a meaningful way and the latest Reuters poll expects a modest expansion in 2012.

There is also increasing evidence that the euro zone debt crisis is knocking some emerging economies off their high perch.

A sharp fall in China inflation reported on Wednesday suggested that policymakers there may, as those in Brazil have already done, start shifting their focus away from inflation and towards supporting growth.

After a brief spurt of strong growth in the quarter just ended based on reconstruction following the devastating earthquake and tsunami in March, Japan's economy is expected to cool into next year.

The strong yen, propped up by fear in global markets that has the upper hand over authorities who are intervening to prevent its rise, is hampering crucial export trade.