What indicates that severe ice conditions are present?

The indication that severe ice conditions are present is best reflected in the effectiveness of de-icing equipment. When de-icing equipment is ineffective, it suggests that the ice accumulation on an aircraft is significant and cannot be adequately managed or removed, pointing to the severity of the ice conditions.

In contrast, minimal ice accumulation would not signify severity; the environment being safe for flight would contradict the presence of severe icing conditions, and trace ice indicates only a light coverage, which is not representative of severe icing. Hence, the inability of de-icing equipment to function optimally serves as a crucial warning sign of severe ice conditions, impacting flight safety and operations.