You don't need to know what it means, only that you have to agree that it is real and is being caused by humans.
Random Dude: You know I really think global warming is a swindle.
"Free-thinking open-minded" Liberal: You retarded brainwashed ass-backwards neo-conservative, if you don't believe in global warming you will destroy the earth and go to hell! Freedom of speech and dissent is only allowed when I agree with it! God bless Karl Marx
Random Dude: I'm not a neo-con or a Republican, I am an independent. I just don't think global warming is the crisis people are trying to make it out to be.
Liberal: Oil shill! You're in Exxon's pocket!
Dissenting Scientist: My research indicates the current global warming crisis may not be all it is cracked up to be.
Employer: You're fired!
Liberals: Oil shill!
Government: You lose all your grants!
Ex-dissenting Scientist: No, I believe in global warming again!