Stock market investors are finally facing up to global turmoil

Early declines signalled acknowledgment of US-China trade war and other events

Stock market investors' ability to ignore big geopolitical events is legendary. Give them a whiff of lower interest rates and most big-picture troubles can be relegated to the status of passing worries. In the absence of cheaper money, however, the story can be different. Tuesday's early declines, which were really a continuation of a losing run that has lasted for most of October, marked a moment when investors were obliged to acknowledge that, yes, some global forces look genuinely alarming.

First, the trade war between China and the US is having an impact that US companies can count. Caterpillar, the manufacturer of earth-moving equipment, said the full-year whack from higher steel and aluminium prices will be about $100m (77m).