Google Earth Community: Earth's magnetic field and declination, 1590-2010

Hi Joey,

>I noted at geomag.org online calculator the US Historic Declination
> dates are from 1750-2010.

The reason for the difference in time span is that they are based on different magnetic field models:
The US Historic Declination Calculator is based on a continental magnetic model of North America, compiled by the US Geological Survey.
In contrast, the GUFM model of Jackson et al (2000) which was used for the Google Earth animations is a global spherical harmonic model based on all available historical magnetic field measurements worldwide.

> Would you have any projections beyond 2012?

You can always project the magnetic field outward beyond 2010 from the present generation of the International Geomagnetic Reference Field. We do not allow this in the online-calculators, but you can do it using the programs on our Models and Software page. Due to the chaotic nature of long-term magnetic field changes, the quality of the prediction will deteriorate increasingly, the further you predict into the future.
The reason why we state that the IGRF-10 and WMM-2005 are only valid until 2010 is because there will be new versions of these models available on Jan-1 2010, and the old models should no longer be used when the updated versions are available.

- Stefan

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