The difference in temperature in the shade and under the sun gives the heat emitted by the sun.Lets look at the wrong answer first:
Dear Tom,
Parade Magazine’s Marilyn Savant says air temperature is the same in the sun as in the shade, but placing a thermometer in the sun heats up the thermometer. Does that make sense? If true, what do they use to measure air temperature?
Mike Beirl, Bolingbrook
Dear Mike,
Air temperature is always measured in a shady location because in the shade the thermometer is measuring the actual air temperature, and only the air temperature. A thermometer placed in the sun measures the temperature that the sun heats the thermometer to, not the true air temperature. When you are in the shade, you are experiencing the true air temperature. In the sun, you are experiencing the true air temperature plus the effect of the sun’s rays on your body, and consequently it feels warmer than just the air temperature.
Thomas Valle, Source
As we have seen, popular science cannot explain the difference of temperature in the shade and sun with scientific data. It explains it with strange explanations, such as the warming of the Thermometer.
Is this the truth? Of course no. In reality, the air temperature is expressed by the formula:
Temperature = Daylight temperature + Sunlight temperature - moonlight temperatureAs we can see, the temperature depends on these three factors and sunlight is one of them. If the moon is not visible or but far away in a day, the effect is zero. Likewise, since the sun is not visible at night, its effect is zero. In exceptional cases, the night effect of the sun is also taken into account.
The effects of both daylight, sunlight and moonlight on the temperature can be easily calculated depends on the distance of the sun and the moon.
Of course, there are other factors that affect the air temperature in a place, such as altitude, distance to the sea, but these factors are not taken into account because they are constant in anywhere.
If you are in the shade, sunlight will have no effect, and in this case the air temperature will be less.
In short, the temperature measured by popular science in the shade is "daylight temperature" and it is erroneous because it does not take into account sunlight.