WHY is it necessary that the wavelength of this solar radiation (especially in the visible range) be changed so that it can be retained as part of the greenhouse warming? What would happen if the wavelength weren't changed?

radiation reaches the earth it must be absorbed by the different living organisms and when using part of its energy is transformed into radiation of greater wavelength (lower energy) that is irradiated by these organisms; This infrared radiation is absorbed by different gases in the atmosphere

Explanation:

The radiation that comes from the Sun has all wavelengths, due to the 5500K sun temperature its maximum emission is 550 nm (green), when this radiation reaches the earth it must be absorbed by the different living organisms and when using part of its energy is transformed into radiation of greater wavelength (lower energy) that is irradiated by these organisms; This infrared radiation is absorbed by different gases in the atmosphere and cannot escape, creating the so-called greenhouse effect.

If the initial wavelength does not change, it would be emitted into space whereby such temperature of the planet will decrease significantly