If one looks at the last interglacial (Eemian) and were to compare it to today's Holocene period you find that temps were several degrees warmer and seas were 20-30' higher than today. This occurred despite the fact that CO2 in Eemian was 280ppm vs today's 420ppm.
Many people talk about the fact the Earth was warmer millions of years ago and CO2 levels were much higher etc. But one doesn't have to go back that far to get a good comparison. The Eemian was a little over 100K years ago and is our most recent datapoint for comparison. The Eemian data proves that it was warmer in recent times with lower CO2 levels.
We are 11.5K or so into the holocene interglacial. Interglacials last perhaps 10-15K years. We may not start the next glacial cycle for thousands of years or it may start up soon. No one knows. But the transition periods in and out of these glacial cycles seem to happen pretty fast based on the data.
If the next glacial cycle were to begin any time soon now THAT would be a major problem. In the last glacial cycle (90K to 20K years ago) 2,000 feet of ice covered New York City.
