(CBS Local) — The Earth is wobbling, and yes, humans are partially responsible.

Scientists working at NASA’s Jet Propulsion Laboratory in California say the Earth’s axis of spin has shifted about 34 feet in the last century.

They cite three major causes, all roughly of equal importance.

The first one is melting ice and rising sea levels, particularly in Greenland. The transfer of weight from places like Greenland to across the globe is causing Earth to wobble more than it would have otherwise.

Another third of the wobble is due to glacial rebound or isostatic rebound, when land masses expand upward as the glaciers retreat and lighten their load. Scientists previously thought was this was the primary contributor to Earth’s wobble.

The final factor is mantle convection, the slow churn of material inside the Earth’s mantle, which is the gooey middle layer of the planet.

Luckily, Earth’s wobble is not large enough to impact our daily life. But, it does give scientists a better understanding of how much humans are changing the fundamental nature of Earth and how it operates.