I found this confusing too. Some ideas: - The recent melts have only been of a relatively small mass of ice, and the two effects on rotation aren't linear, -

I found this confusing too. Some ideas: - The recent melts have only been of a relatively small mass of ice, and the two effects on rotation aren't linear, - There hasn't been enough time for the Earth's shape to have changed in response to the recent ice melts. I'll admit I'm a bit suspicious, though.