7.0 -> 7.2 Migration (oops)

Whups...I just upgraded my linux system from Redhat 7.1 to 7.3. As a part of 
that upgrade my postgres installation was also upgraded from 7.0 to 7.2.1.

Since 7.2.1 databases are not compatible with 7.0, I can no longer start up 
postres.

Is there any way that I can migrate the databases after the fact? Had I 
realized this was going to happen I would have dumped them beforehand, but 
it's a bit late now..

Am I just plain hosed?

Thanks,

..glen