Venus, it seems, would be the upper level...
And a snowball earth the other (which there is some evidence that this extreme was experienced prior to the Cambrian Explosion.)
http://en.wikipedia.org/wiki/Snowball_Earth
The scenario I anticipate is increased warming, disruption of the normal Jetstream, until the influx of fresh water to the oceans disrupts the gulf-stream, and Europe experiences weather like it's partner in latitude, Canada. That will be the new normal.
Did you see the temperatures in Alaska last week?