A new study published Tuesday in the journal Nature found that the Atlantic Meridian Overturning Current — of which the Gulf Stream is a part — could collapse by mid-century or even as early as 2025. Scientists not involved in the study told CNN that the exact tipping point for the critical system is uncertain, and that measurements of the currents have shown little trend or change so far. But they agreed that the results are alarming and provide new evidence that the tipping point could come sooner than previously thought. (Would Laura Paddison, CNN)