What would happen to Earth's temperature if the energy absorbed from the sun (solar radiation) was less than the emitted (thermal) energy leaving the Earth?

The Earth would become cooler until it probably attains a new equilibrium between absorbed solar energy and emitted solar energy.

Explanation:

The earth's energy balance refers to the balance between the energy absorbed from the sun (solar radiation) and the emitted (thermal) energy leaving the Earth. This balance ensures that the earth's surface temperature remains fairly constant.

When energy from the sun reaches the earth, it is absorbed and used by various features of the earth which uses it for their energy needs. Eventually, any excess radiant energy is sent back or emitted from the earth back into space such that the balance between absorbed and emitted energy is maintained.

However, if there is an imbalance whereby more energy is emitted than is absorbed, this would result in the earth losing more heat than it receives. This would result in the earth becoming more significantly colder until it probably attains a new equilibrium between absorbed solar energy and emitted solar energy.