The World Magnetic Model—the standard model of the Earth’s magnetic field and a crucial part of modern navigation systems—was last updated in 2015. That update was supposed to last until 2020, but problems with the model started within a year of the last update. As Nature reports, a geomagnetic pulse under South America in 2016 made the magnetic field “lurch”:By early 2018, the World Magnetic Model was in trouble. Researchers from NOAA and the British Geological Survey in Edinburgh had been doing their annual check of how well the model was capturing all the variations in Earth’s magnetic field. They realized that it was so inaccurate that it was about to exceed the acceptable limit for navigational errors. As a result, the WMM is being updated a year early—this month, in fact, though the U.S. government shutdown is pushing back the release of the updated model.