Career advice in climate change

From a loyal MR reader:

Advice question for you and MR readers, riffing on one of your Conversations themes, if you would indulge me.

What advice would you give to someone wishing to build a career in climate change mitigation as a non-scientist? 

Two advice scenarios: 1) the person is 16; 2) the person is mid-career. Assume no constraints with respect to skill development or self-directed study. That is, what should these people teach themselves? To whom should they reach out to for mentorship?

Your suggestions?