True or False: an increase in solar output is partially responsible for recent warming.

True or False: an increase in solar output is partially responsible for recent warming.

• A. True
• B. False
• C. Cannot be determined
• D. Not addressed

Answer: (B)

The key idea here is attribution of recent warming through radiative forcing. The sun does provide the Earth's energy, but the amount of solar input has not shown a sustained increase over the period of rapid recent warming. Satellite and ground-based measurements indicate solar irradiance is basically flat or varies only within a small range, not enough to explain the clear and accelerating warming observed in recent decades. In contrast, human-made greenhouse gases have risen markedly and trap more heat in the atmosphere, producing a strong, long-term warming signal that matches observations far better than solar changes do. Because solar output hasn’t increased in a way that could drive the recent trend, the statement isn’t supported. Solar forcing is a minor contributor compared with greenhouse-gas forcing.

The key idea here is attribution of recent warming through radiative forcing. The sun does provide the Earth's energy, but the amount of solar input has not shown a sustained increase over the period of rapid recent warming. Satellite and ground-based measurements indicate solar irradiance is basically flat or varies only within a small range, not enough to explain the clear and accelerating warming observed in recent decades. In contrast, human-made greenhouse gases have risen markedly and trap more heat in the atmosphere, producing a strong, long-term warming signal that matches observations far better than solar changes do. Because solar output hasn’t increased in a way that could drive the recent trend, the statement isn’t supported. Solar forcing is a minor contributor compared with greenhouse-gas forcing.