Earth risks tipping into 'hothouse' state:

The planet urgently needs to transition to a green economy because fossil fuel pollution risks pushing the Earth into a lasting and dangerous "hothouse" state, researchers warned on Monday.

If polar ice continues to melt, forests are slashed and greenhouse gases rise to new highs—as they currently do each year—the Earth will pass a tipping point.

Crossing that threshold "guarantees a climate 4-5 Celsius (7-9 Fahrenheit) higher than pre-industrial times, and sea levels that are 10 to 60 meters (30-200 feet) higher than today," cautioned scientists in the Proceedings of the National Academy of Sciences.

And that "could be only decades ahead," they said.