What does Al Gore say canary in the coal mine?

Al Gore uses the phrase "canary in the coal mine" as a metaphor to describe early warning signs of environmental issues, particularly climate change. Just as miners once used canaries to detect toxic gases, Gore argues that certain ecological changes, like the melting of polar ice caps or the decline of specific species, signal broader, impending environmental crises. These indicators serve as urgent calls to action to address the escalating impacts of climate change before it's too late.