If we plot the earth's spectrum on the same graph as that of the sun, we see the earth' radiation is more towards the IR region. Since the earth is colder than the sun, and the wavelength is long, it therefore follows that the higher the temperature of the object, the shorter the wavelength of the energy emitted by that object. The wavelength of maximum intensity radiation grows larger as the absolute temperature of the radiation decreases. The radiation from the sun to earth is fairly constant except during solar storm. Langley is the unit of measure of radiation intensity.
Insolation is the amount of solar shortwave energy intercepted by an exposed surface.
The tilt is important in the sense that insolation varies from the equator to the poles, duration of daylight and the different insolation at a given latitude with season are all due to the tilt. The incoming radiation gets reduced on going through the atmosphere. Insolation losses in the atmosphere could be due to absorption, scattering, diffuse reflection, and reflection. Stress the greatest loss resulting from the clouds. Albedo is dependent on the roughness of the surface, color, soil type, and moisture content of the surface.