Because sometimes, even stupid arguments have to be answered

It's one of the golden oldies by climate change denialists:  "The climate has always changed.   Nothing to see here - move on."

It has never made sense as an argument, and it can be taken as a reliable sign that any person promoting it has never tried to read about the issue seriously and it will be pointless arguing with them.  

But, just in case you know a denialist who is not beyond reason, and who you can forgive for not already realising how vapid the argument is,   Stefan at Real Climate has set out the detailed rebuttal.