You appear to be making up your own narrative here.

In reality, climate science has gone from somewhat uncertain (around 1995: Kyoto) to progressively more certain as measurements have confirmed modellable outcomes.

Our need to change our behaviors has been increasingly important for the past few decades, it's only become an all-out emergency more recently as it's become painfully more obvious that large amounts of humanity are unwilling to change our economic preferences even when faced with obliberation.