What role do clouds play in climate sensitivity and radiative forcing?

• A. Clouds only warm the surface by trapping heat.
• B. Clouds can both cool and warm the surface, and their net effect is a major uncertainty in sensitivity estimates.
• C. Clouds have no significant impact on radiative forcing.
• D. Clouds always reflect sunlight and cause cooling.

Answer: (B)

Clouds change Earth's energy balance in two opposite ways: they reflect incoming sunlight back to space, cooling the surface, and they trap infrared radiation from the surface, warming it. The overall effect depends on cloud properties (height, thickness, droplet size, and coverage) and when and where they form. High, thin clouds tend to let more solar energy through but trap heat, leaning toward warming, while low, thick clouds reflect a lot of sunlight and tend toward cooling. When warming affects cloud formation and behavior, cloud feedbacks can either amplify or mitigate warming, which makes them one of the biggest sources of uncertainty in estimating how sensitive the climate is to forcings. That’s why the best description is that clouds can both cool and warm the surface, and their net effect is a major uncertainty in sensitivity estimates.