In An Inconvenient Truth, the most likely reason the author uses the heading A Silent Alarm is to

Answer 1

create a sense of urgency and importance.

The heading "A Silent Alarm" suggests that there is an imminent danger or threat that may not be obvious or easily noticed. By using this heading, the author aims to catch the reader's attention and emphasize the seriousness of the issue at hand. It implies that although the alarm is silent, it is still ringing and indicating a problem that needs immediate attention. This heading creates a sense of urgency and compels the reader to pay attention to the information presented in the text.