I prefer to think of the "greenhouse effect" as the acceleration of plant growth inside greenhouses, because smart greenhouse owners buy and use CO2 enrichment systems. They burn natural gas to add CO2 to their indoor greenhouse air. That's my accurate use of the term "greenhouse effect".
Unfortunately, "greenhouse effect" is less precise when used to describe how
certain atmospheric gases interfere with Earth's ability to cool itself. Specifically the loss of heat (electromagnetic energy in the infrared frequencies) from the surface of the earth, into space. The atmospheric gases that slow the loss of heat (energy) are mainly noticed as keeping our planet warmer at night than it would be otherwise be. They are called greenhouse gases, and we are stuck with the name.
In 1859, physicist John Tyndall described the greenhouse gas influence using lab experiments. He recognized that water vapor was the dominant greenhouse gas. Water vapor in the atmosphere kept land masses from freezing at night, which would have made vegetable growth very difficult.
I suppose that led to the name "greenhouse effect".
Later experiments, in many different laboratories, refined Tyndall's calculations. Most greenhouse gases interfere with outgoing heat radiation. Each gas affects a narrow range of infrared heat wavelengths, except for water vapor. Water vapor affects a broad range of infrared heat wavelengths. That's why lab experiments, using artificially dried air in a closed system, may not be an actual reflection of what happens in the real atmosphere, which has varying amounts of water vapor.
There had been rising CO2 levels in the atmosphere 1940 to 1975, with global cooling -- no global warming at all. Then global warming began in 1975. In 1979, The Charney Report spun a theory that mild atmospheric warming by CO2, as suggested by the lab experiments, would cause much more warming in the real atmosphere. And never mind 1940 through 1975, which at the time reflected -0.3 to -0.5 degrees C. of global cooling with a rising CO2 concentration ( which is being gradually"adjusted away" in recent decades by government bureaucrats, because global cooling doesn't fit the coming global warming crisis narrative).
The lab experiments suggested a doubling of the CO2 concentration in the atmosphere, which could take over a century, might cause +1 degree C. rise of the global average temperature. Harmless warming. No crisis.
But The Charney Report spun an unproven theory that more CO2 in the air would cause additional warming from additional water vapor in the warmer air, particularly over the tropics. This water vapor positive feedback would allegedly triple the warming caused by a doubling of CO2 alone. And the warming from a doubling of the CO2 would become +3.0 degrees C., from that positive feedback. With an enormous margin of error: +/- 1.5 degrees C. That's usually stated as a range: +1.5 to +4.5 degrees C. of global warming. And that huge, wild guessed, unproven temperature range, is still used today -- 41 years later! No progress in future climate wild guessing!
The water vapor positive feedback would allegedly never stop, causing runaway global warming over time. And that would end life on our planet.
Which would certainly be a real climate crisis if true. The "climate change howlers" got so excited, they declared the world MUST act now to stop climate change. There's no time for more scientific studies to determine if climate change howlers were right or wrong. We must follow their orders, even if they are wrong! Their nonsense "precautionary principle" says: 'Do what we say about fossil fuels, whether we are right or wrong!' That's bizarre logic, and right away you should know they are preaching junk science.
A logical person would immediately wonder why such a water vapor positive feedback did not exist when our planet had a much higher CO2 concentration. Up to 7,000 parts per million CO2 in the past, according to geologists, versus 415 ppm CO2 today? Why would the earth still support life today, if there was really a water vapor positive feedback? Why was there no runaway warming in the past, when there were much higher CO2 concentrations? The answer: ' How dare you question authority, you "science denier! '
In addition, measurements of the troposphere, where the greenhouse effect occurs, by satellites since 1979, found a water vapor positive feedback does NOT exist. There was no significant amplification of warming from water vapor over the tropics, or anywhere else.
As the concentration of a greenhouse gas increases, its ability to cause a change in atmospheric temperature declines. This is called "saturation,". and it is fairly represented by a logarithmic curve. CO2's ability to disrupt atmospheric cooling begins to decline even below 100 ppm. At 415 ppm today, CO2's effect is small -- close to full saturation. Meaning ever larger increases in CO2 are needed for a minor atmospheric warming. Now remember that disruption of Earth's cooling by CO2 in the atmosphere is assumed, based on lab experiments, not proven in any way. The assumption is reasonable, but not a fact.
Calculations by scientists van Wijngaarten and Happer across the infrared absorption frequencies of H2O (water vapor), CO2 (carbon dioxide), CH4 (methane) and N2O (nitrous oxides), generally agree with satellite-based temperature measurements. The scientists showed that absorption by CH4 and N2O are negligible, regardless of climate alarmist claims.
Van Wijngaarten and Happer use the high-resolution transmission molecular absorption database (HITRAN). That database simulates the transmission and emission of light in the atmosphere, to calculate the influence of a doubling of the CO2 concentration, and a 6% increase in water vapor in the atmosphere.
The scientists arrived at an upper bound of +1.5 degrees K (C), more likely to be around +1 degree C., agreeing with what lab experiments in artificially dried air, and actual atmospheric measurements by satellites, had suggested. And +1 degree C. is less than the lowest range (+1.5 degrees C.) estimated (wild guessed) by the UN Intergovernmental Panel on Climate Change (IPCC) and its supporting computer gamers around the world ... er ... I mean climate modelers.
More information about HITRAN here:
https://hitran.org/about/