Myth: Sea levels were much higher millions of years ago

3 million years ago, sea levels were 10 metres higher than they are today, yet CO₂ levels were roughly the same as now. So, why aren’t sea levels 10 metres higher in the 21^st century? This is proof that they are unrelated to CO₂. 

Fact:

Sea levels have a long lag time following temperature increases. It may take hundreds of years before they reach their peak, but the evidence suggests that this is the direction they are headed. At current rates of temperature increase, scientists expect a rise of up to one metre by the end of the century, with more coming after that.