Economist Nouriel Roubini says the much feared double-dip recession has already arrived.

"Whatever letter of the alphabet U.S. economic performance ultimately resembles, what is coming will feel like a recession," Roubini writes on project-syndicate,org.

"Mediocre job creation and a further rise in unemployment, larger cyclical budget deficits, a fresh fall in home prices, larger losses by banks on mortgages, consumer credit, and other loans, and the risk that Congress will adopt protectionist measures against China will see to that."

At best, Roubini says, “we face a protracted period of anemic, below-trend growth in advanced economies as deleveraging by households, financial institutions, and governments starts to feed through to consumption and investment.”

And at the global level? Well, the countries that spent too much – the United States, the United Kingdom, Spain, Greece, and elsewhere – now need to deleverage and are spending, consuming, and importing less.

However, countries that saved too much – China, emerging Asia, Germany, and Japan – are not spending more to compensate for the fall in spending by deleveraging countries.

“Thus, the recovery of global aggregate demand will be weak, pushing global growth much lower,” Roubini says.

“Fasten your seat belts for a very bumpy ride.”

However, some economists say investors are suffering from "Armageddon hypochondria" if they think the global economy is headed for a double-dip recession.

For example, economist Adam Carr says that the world economy is clearly improving.

"There's a strong V-shaped recovery going on," Carr told the Sydney Morning Herald.