Assertion: magnetic field | /r/CapableOf | weaken over the top of north america
Facets:
value: by about 3.5 percent
type: OTHER
value: since 1999
type: TEMPORAL
Source sentences:
text: Presenting at the annual Living Planet Symposium in Prague last week, ESA researchers showed that the magnetic field has weakened by about 3.5 percent over the top of North America since 1999, but has strengthened by roughly 2 percent over Asia in that same time period.