In Europe , Britain's FTSE 100 shed 0.5% in early trading. Germany's DAX dropped 1% after the ZEW indicator of economic sentiment for August plunged.

Nervous investors are piling into gold and ultra-safe government bonds. The 10-year US Treasury yield is below 1.7%, its lowest level in nearly three years. The 30-year Treasury yield is nearing an all-time low.

2. Singapore GDP: Singapore is headed for its weakest annual growth rate in a decade. It's blaming its troubles on the US-China trade war.

The country warned Tuesday that economic growth could fall to 0% this year. Previously, it predicted its economy would grow by 1.5% to 2.5%.

That kind of growth would be the worst since 2009, when Singapore's GDP contracted by 0.6%, according to the International Monetary Fund.

The global growth outlook has weakened in part because of escalating trade tensions between the United States and China, Singapore's Ministry of Trade and Industry said.

A recession looks unavoidable for Singapore, Sian Fenner, lead Asian economist for Oxford Economics, wrote in a research note.

3. Argentina's rout: Emerging markets are back in the headlines after a surprise result in Argentina's primary election sent the country's currency and stocks plunging on Monday.

The fear from investors: that populists could replace the country's current, business-friendly government.

The country's Merval index closed down 38% while the Argentine peso plummeted 15% against the dollar. In an already volatile moment, such massive losses are putting investors on edge.

4. Coming soon: A new Before the Bell, packed with insight from CNN Business reporters and trusted experts. If you're not already getting our emails, A new Before the Bell, packed with insight from CNN Business reporters and trusted experts. If you're not already getting our emails, click here to sign up for a redesigned newsletter that delivers the news, analysis and market charts you need to start your business day right.