Most scientists believe that climate change is primarily caused by human behavior. Although, there are some experts who disagree.
Explanation:
The above sentence shows that some scientists disagree that human behavior is one of the main causes of global warming, even if most scientists agree. In this case, the best word that completes the blank space and maintains the coherence of the sentence is the word "although". This is because this word expresses the meaning of "in spite of something", showing that even though most scientists blame the human being, there are still scientists who disagree.
