Don't think 6 million would be enough, the max temp and co2 levels of the Cretaceous was 66 million years ago, and the Cretaceous period was 145-60 million year

Don't think 6 million would be enough, the max temp and co2 levels of the Cretaceous was 66 million years ago, and the Cretaceous period was 145-60 million years ago. That perioid may be a somewhat large peak in a co2 graph, making the current co2 increase look negligible. However ocean levels are also estimated to have been 50-100 meters higher than today at that period, along many other side effects.