NEW YORK (TheStreet) -- Global growth will shrink due to the U.K.'s vote to leave the European Union (E.U.) last week, which initially sent markets across the world into turmoil, Credit Suisse chief economist James Sweeney told CNBC's Joe Kernen on "Squawk Box" Thursday.

Global markets, including the U.S., have since begun to recover this week. The Dow Jones opened higher by about 38 points today, after closing down by 611 points on Friday. The S&P 500 is rising by around 5 points and the NASDAQ is climbing by about 12 points early this morning.

Kernen asked Sweeney about his forecast for France, Portugal, Italy, the E.U. Scotland, Ireland and Northern Ireland, "There are a lot of things to work out here, do you have any idea how it finally shakes out?"

"Uh, no, but I think the answer is lower in terms of global growth forecasts, in terms of European growth forecasts," Sweeney answered.

When asked about negative bond yields, Sweeney argued that they have been sharply declining before the Brexit so his main concern now is "risky asset prices moving lower too later on."

"Because there's some markets, like bonds, which have clearly adjusted and there's others which think nothing happened at this point," he continued.

Kernen pressed as to which assets are considered to be risky at this point.

"Well typically if you get a slowdown in global growth, commodity prices are sensitive, emerging markets are sensitive, credit spreads are sensitive and we really haven't seen a lot of that so far," Sweeney explained.

Kernen wondered if this does not show that maybe there is not as "pronounced an issue" from Brexit as Sweeney predicts.

"I don't think the markets are so efficient that they have more information on what's happening (than economists do)," Sweeney argued.

"I think you're going to have a bit of a negative shock in global growth," he commented, when asked if the U.K. could benefit from Brexit in the long term.