I've read that a "Snowball Earth", like other "Snowball Planets", would never recover. Reflection of the Sun's energy from its frosty-white surface would prevent...um...Global Warming.
Except Earth is just big enough to have an radioactive core of molten iron and nickel. Some say the Earth actually consumed another smaller proto-planet that caused enough crustal ejecta to form the moon itself.
The Earth in it’s snowball form had so much activity going on in the mantle and crust that volcanoes below the ice erupted through them and displaced trillions of tons of CO2 in to the atmosphere, warming it enough to expose land that then itself had a warming effect to lower planet-wide reflective albedo.
That is, until some giant alien comes along and pours some kind of flavoring on the ice...