The last time there were no ice caps, humanity didn't exist. That was 3 million years ago: https://slate.com/technology/2014/12/the-last-time-the-arctic-was-ic

The last time there were no ice caps, humanity didn't exist. That was 3 million years ago: https://slate.com/technology/2014/12/the-last-time-the-arctic-was-ice-free-in-summer-modern-humans-didn-t-exist.html https://slate.com/technology/2014/12/the-last-time-the-arcti... Earth has been cycling between glacial (90,000 years) and inter-glacial periods (10,000 years) every 100,000 years or so for the past million or so years. We were actually winding up an interglacial period and would likely be headed to another ice age...in a few thousand years. But our CO2 emissions completely changed that trajectory in two centuries. Our current emissions will change that trajectory even further in just a couple decades. Now we are headed for something...very different. And it's happening fast.