Re: Snowball earth, when and why it happened.

Its the speed of change between iceless and snowball earths
that matters. In the past the earth has been glaciated about ten
percent of its history. We've been in one of those rare era ice age
eras for the past 27 million years. "Normal" is no polar ice cap at
all.

However it takes hundreds of thousands to millions of years
to transition between the two conditions. The current melting
is only a century or so. That stress civilization and ecologies.


.