Weather Forecasting has only existed as a measurable science since the 19th Century. That is the 1800’s for those that aren’t that good at math. Many of the details came about during the wars of that period. It is easier to plan a battle if you have an idea of what the weather is going to do on the battlefield.
Record keeping also was not accurate prior to the 18th Century at the earliest. So exact temperatures and other climate conditions prior to the creation of the scales in use today are not reliable as they are vague and use approximations.
If one believes that science can predict that temperatures will be drastically and apocalyptic to harm human life 20 to 100 years in the future. Why cannot these same scientists give us the exact temperature and climate (weather) conditions for tomorrow or next week?
We are looking at mostly 200 years of accurate data of conditions and then applying that to the future without taking into account the previous 4 billion years of climate conditions and cycles that the world has gone through. Such a trivial window of data is hardly scientific by any standard. And applied to any other hard science would be laughed at by all parties.