Small headlines add up to big stock losses

Pisani's market opens to the downside

You might have woken up this morning and checked U.S. stock futures. You might have noticed they were down roughly 1.5 percent and wondered, "What happened between the close yesterday and overnight that made futures go down 1.5 percent?"

The answer is, not much. There have been no big headlines. Just a few small ones that, collectively, have added up.

Some traders have pointed to a new report from the Asian Development Bank (ADB) that lowered Asian growth forecasts for 2015 and 2016 on softer prospects for India and China.

The ADB now sees GDP for China at 6.8 percent in 2015, down from 7.2 percent earlier. India is projected to grow 7.4 percent, down from an earlier 7.8 percent forecast earlier.

Read More ADB slices Asia growth forecasts

There was the usual discussion of the knock-on effects of slower China growth on Southeast Asia, as well as soft global commodity prices which puts pressure on Asian commodity-focused export economies like Mongolia, Indonesia, Azerbaijan, and Kazakhstan.

Still, stocks in China ended up fractionally.

European markets opened down modestly and have drifted steadily lower. The dollar is modestly higher, but commodities like copper also began trading lower overnight and have also drifted lower through the morning.