The global markets are at risk of crashing when the dollar rebounds, says economist Nouriel Roubini.

Roubini, a professor at NYU, is credited with long predicting the financial collapse of 2007 and 2008.

“In the short run what’s happening is there’s a wall of liquidity, not just in the U.S., but around the world, that is chasing assets,” he told CNBC.

“It’s equities, it’s commodities, it’s credit, it’s gold, it’s emerging market asset classes.”

And what does that amount to? “Now we are in the mother of all carry trades," Roubini says.

“Everybody is shorting the dollar, borrowing and investing in assets all over the world.”

That activity helped push the greenback to a 14-month low.

But there’s a risk in this, Roubini says.

“People are borrowing at zero percent interest rates in the U.S. Effectively the rate of borrowing is negative, because we have the dollar falling. You have a capital gain,” he explains.

“You are buying any assets around the world. All these assets are perfectly correlated.”

Eventually, the dollar will rebound, Roubini says.

“Once the dollar stops falling, you have a sudden reversal of the dollar, you have to close your shorts, you have to dump assets, and you could have a market crash all over the world,” he says.

Most experts see a global crash as unlikely, but they say substantial problems remain.

Have we learned the appropriate lessons from the financial crisis?

“The early signs are mixed at best,” William Galston of the Brookings Institution writes on the think tank Web site.