In message .com,
adder1969 writes
I have some climbing/rambling roses which I thought had no thorns,
having pruned them for years and never noticed any but yesterday I was
out snipping and ouch! So what's going on? Some growth has thorns
and some doesn't!

Possibly you have suckers from the rootstock. Alternatively a sport,
perhaps a reversion to the parental type.
--
Stewart Robert Hinsley