If the atmosphere traps heat, how does cool-down occur at night? Trapping was needed to convert a noneffect into a danger.

Here's why there is no such thing as a greenhouse effect in the atmosphere:

All matter emits radiation constantly including the atmosphere, which is a cooling mechanism. There is no trapping with radiation emission.

 
The use of the word trapping is a fraud upon the public designed to create the subject of greenhouse gases existing in the atmosphere. Without the word trapping, the subject does not exist.

With the atmosphere emitting radiation constantly, the air will cool 10 to 20 degrees in a few hours during clear nights, because a transparent gas emits radiation much more readily that an opaque solid such as the surface of the earth. With heat moving through the atmosphere that fast, a small amount isn't going to be trapped in place.
 

 
Only one CO2 molecule in 2,500 air molecules (at 400 parts per million CO2) is absorbing the unusual radiation.
 

 
If five air molecules radiate away the added energy, while one CO2 molecule absorbs, the added energy is gone and the other 2,495 air molecules surrounding each CO2 molecule are not affected. There cannot be a significant temperature increase in the atmosphere when 2,495 air molecules surrounding each CO2 molecule are unaffected by the process.

In other words, each carbon dioxide molecule would have to be 2,495°C to average 1°C temperature increase, but the CO2 would only be 0.03°C warmer than the surrounding air molecules.

Emitted radiation (black body infrared radiation) is 12 times stronger than the radiation absorbed by carbon dioxide. It means the energy is emitted as fast as it is absorbed.

Absorbed radiation in the atmosphere is re-emitted in 83 femto seconds, average. Heat absorbed by everything else in the atmosphere is re-emitted in 83 femto seconds, average. There is no difference. What then is trapping heat in the atmosphere?

(Heat can accumulate in the atmosphere short-term, because conduction and convection can put heat into the atmosphere faster than radiation can emit it; but radiation does not put heat into the atmosphere faster than radiation can emit it.)

It means there is no such thing as a greenhouse gas trapping heat in the atmosphere. There are other explanations for weather effects.

Faking The Numbers

Physicists claimed 40 times too much radiation leaving the earth and creating global warming. Reduce the radiation by a factor of 40 and the calculated global warming reduces by a factor of 40. Instead of 1°C heating, the calculated heating so far should be 0.025°C.

Only 1-3% of the energy leaving the surface of the earth should be radiation with 97-99% being conduction, convection and evaporation. (The sun's energy is too high of a frequency to be absorbed by carbon dioxide.) No one would hear a word of greenhouse gases with so little radiation. So physicists used an erroneous Stefan-Boltzmann constant to show 79% of the energy leaving the surface of the earth as radiation and only 21% as conduction, convection and evaporation.

A white hot light bulb could not emit 79% radiation without a vacuum environment, yet physicists claim the cold surface of the earth, which averages 15°C or 59°F, emits its energy as 79% radiation.
 

Only 8% of the radiation emitted by the earth (infrared, black body radiation) is absorbed by carbon dioxide in the air and there is almost no radiation emitted by cold surfaces such as the earth.

Having no science to work with, physicists contrived radiative transfer equations to calculate the heating caused by carbon dioxide in the atmosphere. The result shows 3.7 watts per square meter of heating upon doubling the amount of carbon dioxide in the atmosphere. There are no square meters in the atmosphere, but the Stefan-Boltzmann constant was needed for calculating radiation, and it uses watts per square meters. The equation indicates that doubling the CO2 from one molecule to two molecules would do the same thing creating 3.7 W/m² through the entire atmosphere. So physicists set limits in the usual range, but it shows the fakery of the calculations.