escalate vs step up

escalate

verb
  • To increase (something) in extent or intensity; to intensify or step up. 

  • To climb. 

  • In technical support, to transfer a customer, a problem, etc. to the next higher level of authority 

step up

verb
  • To increase, augment, or advance, especially by one or more steps. 

  • To assume or take responsibility. 

How often have the words escalate and step up occurred in a corpus of books? (source: Google Ngram Viewer )