climatic, climactic

Climatic or climatic means having to do with the weather, or changing weather patterns or conditions--
Our ambassador wants to discuss climatic change with their president.
The lower crop yields are due to soil depletion; climatic changes have not affected the crops.

Climactic or climactic means having to do with the highest or most intense point; the climax--
There was a brief period of climactic tension, then everyone started yelling at once.
He is at a climactic point in his career; he's afraid he'd miss something while away on vacation.

Now that you know that, you can say--
"The climactic point of the argument came when he denied the existence of climatic change."

Note--"climacteric" means a critical period or phase--
He believes that next year will be a climacteric, and that his life will change drastically.
It will take another two weeks for this fruit to reach its climacteric.