"There are dozens of climate models, and for decades they’ve agreed on what it would take to heat the planet by about 3° Celsius. It’s an outcome that would be disastrous - flooded cities, agricultural failures, deadly heat - but there’s been a grim steadiness in the consensus among these complicated climate simulations.
"Then last year, unnoticed in plain view, some of the models started running very hot. The scientists who hone these systems used the same assumptions about greenhouse-gas emissions as before and came back with far worse outcomes. Some produced projections in excess of 5°C, a nightmare scenario."
The problem is, scientists couldn't figure out why the new models showed an acceleration of the problem, or the degree (no pun intended) to which they needed to be taken seriously.
More from the story:
"The reason for worry is that these same models have successfully projected global warming for a half century. Their output continues to frame all major scientific, policy and private-sector climate goals and debates, including the sixth encyclopedic assessment by the UN’s Intergovernmental Panel on Climate Change due out next year. If the same amount of climate pollution will bring faster warming than previously thought, humanity would have less time to avoid the worst impacts."
Like I said. Worth reading. Here.