If there was no CO2 in Earth's atmosphere, what would likely be the state of the Earth's surface temperature?

If there were no carbon dioxide (CO2) in Earth's atmosphere, the surface temperature would likely be less than it is now. CO2 is a greenhouse gas, meaning it plays a crucial role in trapping heat in the atmosphere. It contributes to the greenhouse effect, which keeps Earth's climate warm enough to support life.

With zero CO2, the greenhouse effect would be dramatically reduced, resulting in an inability of the atmosphere to retain heat effectively. Consequently, the planet would lose heat rapidly at night and during certain periods, leading to much colder surface temperatures. This cooling effect would undermine the stability of current habitable conditions, pushing temperatures significantly lower than present levels.

The other choices hint at stability, variability, or higher temperatures, which are not plausible due to the absence of a critical component of the atmosphere that aids in temperature regulation. Therefore, the scenario of no CO2 aligns with a much colder Earth, making this answer the most accurate reflection of the potential consequences.