When I was in the eighth grade, our science class did a simple little experiment just to teach us data collection and analysis methods. The experiment went something like this:

1. Fill a beaker halfway with cold water, and then put in some crushed ice. Wait a few minutes then check the temperature. Keep checking the temperature until it drops well below the freezing point.

2. Put the beaker over a flame and record the temperature of the ice water every 15 seconds. Keep doing it after all the ice has melted and until the water starts to boil.

3. Draw a chart of temperature versus time. Label the points when the last of the ice melted and when the water started to boil, etc., etc.

What I remember distinctly from this experiment is that the water temperature didn't really start to rise until all the ice was gone. The water temperature stayed around 4 degrees Celcius untill all the ice was gone. Then the temperature shot up rather astonishingly fast.

The point is, the Earth's polar ice sheets have been retreating for thousands of years. The ocean currents constantly circulate past them before heading back toward the equator. When all the ice is gone....

It may just be a coincidence that this happens when humans invent industry and start burning fossil fuels. Just my two cents.