climate canary
n. A natural phenomenon or event that signals a looming environmental disaster caused by climate change.
They are dubbed the "climate canaries" — the people destined to become the first victims of world climate change. And as government ministers sit down in Nairobi at this weekend's UN Climate Conference, the people most likely to be wiped out by devastating global warming will be only a few hundred miles away from their deliberations.
—Peter Beaumont, “African nomads to be first people wiped out by climate change,” The Observer, November 12, 2006
The British Antarctic mission this week told us CO2 levels were at their highest in 800,000 years. We don't know at what level the world would reach a "tipping point" beyond which any action we took to manage global warming would become harder or impossible. But the Antarctic climate canary is chirping.
—Peter Neilson, “Penalties loom for those who ignore carbon crisis,” The National Business Review, September 08, 2006
2000 (earliest)
Glaciers can signal climatic changes, though Driedger said not enough is known to view glaciers as climate canaries, signaling new ice ages or warming trends.
—Mike Archbold, “Geologists have been following Nisqually's changes since 1840,” South County Journal, January 05, 2000
This term comes from the phrase canary in a coal mine, which refers to the now mostly defunct practice of keeping a canary or two in a mine as an early warning device. Canaries are more sensitive than humans to toxic gases, particularly carbon monoxide, which to us is odorless, tasteless, and colorless. If a canary showed signs of distress or even died, the miners would know that something toxic was in the air and they wouldd evacuate the mine.