NASA Debunks 2012 Apocalypse With New FAQ

If you really want to provide a counter in these types of discussions it is more helpful to speak in their language. My favorite example of this was when last year astronomers announced that the zodiac signs were incorrect due to a shift in the planet's position relative to the sun since the time that the zodiac was created. This produced more reverberations in the astrological community than any number of studies showing the falsehood of their predictions.

In this case, it may be helpful to point out that the December 21 is simply the date at which the next cycle in the Mayan calendar begins, as occurs every 400 years or so, and that the Mayans themselves made no predictions about cataclysmic events occurring on these dates.

Not well supported. Magnetic reversals happen every few hundred thousand years, so by that measure there's a 1% chance it will happen in the next few thousand years. The mechanism is not well understood, it has been unusually long since the last flip, and the poles have shown significant activity in the last hundred years. It's hard to assign a probability less than 1%, and there are plausible arguments for higher.

http://www.nasa.gov/topics/earth/features/2012.html

http://farsight.org/demo/Demo2008/RV_Demo_2008_Page1.html

Mind you, these remote viewers are said to be used by military, so probably not a complete hoax.

Anyway, if time travel is possible then the future is changeable. Let's be optimists.