When we think of rising sea levels, we think of global climate change and melting ice caps. Yet there's a disparity in the raw data. During the second half of the last century, global sea levels rose 1.8 millimeters per year, according to tide gauges. But it's been determined that melting ice caps and glaciers have only contributed to 1.1 millimeters per year of that. So where did the other 0.7 millimeters come from? A new study has a remarkably simple answer: from you.