When does climate change become dangerous?

H

ow much does the climate have to change for it to be “dangerous”?

This question has vexed scientists ever since the first climate models were developed, back in the nineteen-seventies.

It was provisionally answered in 2009, though by politicians rather than scientists.

According to an agreement known as the Copenhagen Accord, which was brokered by President Barack Obama, to avoid danger, the world needs “to hold the increase in global temperature below 2 degrees Celsius” (3.6 degrees Fahrenheit).

Read The New Yorker story - “A New Climate-Change Danger Zone?”