Subject: What difference does a change in the earth's orbit make

I know that the earth orbits the sun in an eliptical orbit that is constant ...
or rather, changes very, very slightly over the course of many years.
But I once heard that if the entire orbit was reduced by a distance of a few 
centimeters, that this would drastic changes in the weather patterns on earth.
Infact, that is what causes the ice age's that the earth had every so many 
hundreds of thousands of years.
So my question is, it true that a change of afew centimeters in the earths
orbit could cause drastic changes on the earths weather?

Re: What difference does a change in the earth's orbit make