What term describes long-term climate forcing due to orbital variations?

• A. Orbital forcing
• B. Radiative forcing
• C. Anthropogenic forcing
• D. Greenhouse forcing

Answer: (A)

Orbital forcing describes how changes in Earth’s orbit and tilt—eccentricity, obliquity, and precession—modulate the amount and distribution of sunlight the planet receives over long timescales. These Milankovitch cycles drive climate variations on tens to hundreds of thousands of years, shaping glacial and interglacial periods. This is distinct from radiative forcing, which is a general measure of any change in Earth’s energy balance from various causes (natural or human), and from anthropogenic or greenhouse forcing, which refer to human-caused changes. So, the term that specifically captures long-term climate forcing due to orbital variations is orbital forcing.