The world is 'perilously close' to tipping points of irreversible climate change. These are 5 that keep scientists up at night. - USA TODAY

The world's scientists say the climate change crisis is upon us. Unless we act now, crucial planetary systems are on the cusp of irreversible damage.

Five years ago, the United Nations' panel on climate change was charged with drafting a series of reports detailing its science, the effects on the planet and how humanity might save itself. The las… [+203 chars]

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