5. If the earth warms significantly, the polar ice caps will melt. Water will move from the poles, near the earth’s rotation axis, and will spread out around the globe. a. How will this change the earth’s moment of inertia?

Before the polar ice caps melt, the ice will have no effect on the earth's moment of inertia because it's distance from the axis of rotation is close to zero.

When the ice melts, the moment of inertia will increase because the mass of ice is spreading out around the whole earth.