jesus lando, what has 'happened' already that wouldn't be consistent with a null hypothesis?
literally nothing! Every 'negative consequence' that is even partially attributable to climate change is easily within the realm of natural variation of earth's longrun climate so far.
Our records only go back a few hundred years in the best case scenario, and societal humanity has existed for at least thousands if not tens of thousands of years.
Are our actions changing the environment? Certainly. The question is: is it worth it? That is a different question where the answer is always assumed.
That's why on one argues about whats happened already - because the answer is clearly YES ITS WORTH IT.
The argument requires it to get much, much worse before climate alarmists can be justified in the urgency of their message.