Asked by: Max Jones, USA
The Earth’s axis isn’t perfectly upright relative to its orbit, but instead is tilted at an angle of around 23.5°. This so-called obliquity has long been known to change slightly over thousands of years as a result of the gravitational influence of the Sun, the Moon and the other planets. But evidence is also emerging for effects resulting from climate change.
In 2013, researchers at the University of Texas reported that satellite measurements had revealed that the Earth’s tilt is being affected by the shift in mass caused by the melting of ice covering Greenland. The team found that around 15 years ago the Earth’s axis began to move east and then south. Earlier this year, researchers at NASA’s Jet Propulsion Laboratory confirmed the effect, and added another cause: changes in the amount of water stored in the Earth’s continents. Lower rainfall over Europe and Asia in recent years seems to be adding to the axial drift.
So is man-made global warming to blame for these changes? According to the JPL team, it’s probably just part of the Earth’s natural climatic rhythms. Either way, the effect isn’t anything to lose sleep over: the recent shift amounts to less than one-millionth of the Earth’s total tilt angle.