alarm

"There were these pressure alarm mats, but as soon as you stood on them, they would slip from underneath your feet – they were used as preventions, but were actually causing the falls."

Instead, he got an alarming lesson in current events.

Across the mining station, alarms were blaring and lights were flashing red.

Given the party’s ideological tinge, this was deeply alarming.

According to Dr. Abram, the sharp decline in Antarctic sea ice is another alarming signal.