Radiative forcing measures the change in Earth's energy balance due to a driver; a positive forcing leads to what?

• A. Cooling
• B. Warming
• C. No Change
• D. Either Depending on Driver

Answer: (B)

Radiative forcing is about how a driver changes the balance of energy entering and leaving the Earth-atmosphere system. When this forcing is positive, more energy is absorbed than is emitted back to space. That net gain of energy warms the surface and the lower atmosphere over time.

Think of greenhouse gases as traps for infrared radiation: they slow the loss of heat to space, increasing the downward longwave flux and the overall energy that stays in the system. Other positive drivers, like a reduction in reflectivity (albedo) or more solar energy reaching Earth, also push the balance toward warming. Conversely, negative forcing (for example, volcanic aerosols that reflect sunlight) reduces the energy input, leading to cooling.

So, a positive radiative forcing leads to warming.