As the planet warms, it risks crossing catastrophic tipping points: thresholds where Earth systems, such as ice sheets and rainforests, change irreversibly over human lifetimes.

A report warns that coral reefs may have reached their tipping point, and ice sheets, ocean currents and the Amazon are at growing risk. But, what does that actually mean?

Urban jungles don’t have to mean concrete wasteland. Some metros are setting new standards of what city living can be. Yes, ...