Tornado Alley (PROG)

[jsc52033]

irregardless the earth is warming. My stratigraphy prof taught that
it was due to a number of things volcanos and the rotaion of the eath
which could at times bring it closer to the sun. His theory was that
man could not generate sufficent poloution to trap the heat generated
by all of the natural occurrences which occured 4 times before.
So hows do the current scientists explanin the previous global warnings
which melted the previous ice ages?