Why?
Climate science works with quantative models and makes concrete predictions.
So if the predictions don‘t come true the model is false.
E.g. this random blog I found googling compares IPCC predictions with actual outcomes: https://johncarlosbaez.wordpress.com/2012/03/27/the-1990-ipc...
[the link is just supposed to show how climate science is falsifiable. I have no idea whether the numbers in this specific source are trustworthy]