Of course it's true.
It's only the rate at which it is changing and the results of those changes that is in doubt.
From what I can discern, by the time it is of pressing concern, those who have become too hot will have had time to walk north ( or south , depending on hemisphere) and those who wish to live at lower elevations will have had time to learn to tread water.
Neither, i reckon its going through phases - but with the terms being much longer than seasons as we know them. For instance however many thousands of years ago we had the ice age etc, and then it warmed up so i reckon it will all come around again in a cycle. Just a thought !.
Watch out for those dinosaurs !.