Why are water vapor carbon dioxide methane and nitrous oxide called greenhouse gases?

Greenhouses are glass houses that you grow plants in during cold weather. The glass allows the sunlight in to heat it up. There are gases in the upper atmosphere that have the same effect that they hold the light in and heat up the atmosphere.

A:In the beginning someone said "these gases keep the earth warm 'like a greenhouse'" meaning they absorbed the sun's heat.

Later some non-science person thought that the gas floated to the top of the atmosphere to form a layer like the glass in a greenhouse.

The popular view is that the atmosphere has some sort of layer of carbon dioxide "up there" that reflects heat back down to Earth rather than letting it escape to space. That would be like the glass on a greenhouse trapping warm air in while letting the sunlight through to increase the heat. In a greenhouse the sunlight warms the benches and floor, he warm objects heat the air, the air is trapped by the double layer of insulating glass.

It does not happen that way.

Sunlight comes in and warms the Earth's surface. It warms the gases in the air too, at least some of them with a bond size that gets excited by sunlight. These special gases are greenhouse gases (carbon dioxide, methane, water vapour and a few others). They are mixed evenly through all of the atmosphere (not in layer). When the gases are warm they share their heat with all their gas molecule neighbour and heat the atmosphere generally.

The effect is more like wet sand in a microwave. Microwaves do not heat sand. They do heat water. When you microwave wet sand, the water heats up - might even turn to steam. The hot water warms the sand.

Aside: The question "How is the atmosphere like wet sand in a microwave oven?" has not been asked.

A:Greenhouse gases are called so because they cause the greenhouse effect by absorbing the infra red rays and do not allow these rays to escape the atmosphere of the earth, hence leading to an average increase in the temperature of the earth. This effect is deliberately induced in a greenhouse. Thus, the name.

because they work like a green house slowly heat up and don't let heat out

It's called a greenhouse gas because it works like the glass in a greenhouse, or glasshouse for plants, keeping the heat in and not allowing it to escape.

We have probably seen during winter plants are kept in a greenhouse, or a place which is covered with glass. When heat and light enter this house the glass does not allow the heat to go back. The heat is retained and keeps the plants warm. Similarly, when heat and light from the sun enter our atmosphere, some gases like carbon dioxide, methane and nitrous oxide do not allow the heat to reflect back into space (like the glass sheet). These are the greenhouse gases.

Because they cause the atmosphere to act as a greenhouse, trapping heat inside.