ABC radio presenter Adam Spencer has been told to "shut up" and stop being childish during a heated on-air exchange with climate change sceptic Christopher Monckton.

In what was more a debate than an interview on 702 ABC Sydney, Spencer hung up on his guest before Monckton called back and the interview resumed.

The tension began when Spencer asked Monckton about his claims that he is a Nobel laureate.

Monckton said he was given a pin by a US professor who felt he deserved one for his work and he sometimes wore it as a joke.