Water is an essential ingredient of the earth, and without it we would not be here. Water reshapes our planet’s surface through erosion and chemical weathering; the position of the shoreline is one of the most changeable of all geological features. Although it may not feel like it, we are living in an ice age now. At the moment we are in a warm period and the sea level is high. Fluctuations in climate have caused sea level to vary by as much as 400 feet over the last two million years. One of the most astonishing recent discoveries is that the history of global sea level over this period is contained in the composition of tiny organisms preserved as fossils on the sea floor, and furthermore, that the growth and decline of the ice sheets are related to the nature of the earth’s orbit around the sun. (60 minutes)