Markets fall as volatility spikes

Markets were mostly lower on Tuesday.

The S&P 500 fell 0.2 percent, the STOXX Europe 600 fell 0.7 percent and the Nikkei 225 was flat.

However, the Shanghai Composite jumped 1.1 percent even as the Caixin/Market manufacturing PMI fell to 50.6 in August, its lowest level since June 2017.

Meanwhile, Brian Sozzi at TheStreet is optimistic about the US stock market, at least for September.

"While we may certainly see some profit-taking, a meltdown is unlikely given the fundamental backdrop of Corporate America," he wrote. "Stocks are soaring because profits are doing the same," he quoted Yardeni Research founder Ed Yardeni as saying.

Other investors may not share the optimism. Volatility rose on Tuesday, with the VIX jumping 9.5 percent.

"A set of reports hinting at slower economic growth, an inflation spurt, or perhaps a little of both could quickly bring a new era of failing fundamentals," Jim Paulsen of the Leuthold Group wrote in a note on Tuesday.