Our planet had more carbon dioxide (CO2) in the atmosphere than it does now, for most of its 4.5 billion year existence.
Most of that CO2 is now sequestered underground as the carbon in coal oil, and natural gas. As we burn those fossil fuels, the CO2 is "recycled" back into the atmosphere.
That's good news. Because plants on our planet prefer 1,000 ppm CO2, not the current 415 ppm CO2. Many greenhouse owners supplement the air inside their greenhouses to about 1,000 ppm CO2, to grow their plants faster, and with less water too. More CO2 in the atmosphere will optimize plant growth on our planet. Optimizing plant growth will support more life on our planet. Anyone who wants to limit CO2 in the atmosphere is anti-life.
The climate alarmist theory is that adding CO2 to the atmosphere would lead to more water vapor in the atmosphere. Water vapor is the primary greenhouse gas. More water vapor in the air should cause global warming.
Climate alarmists claim adding CO2 to the atmosphere leads to a water vapor positive feedback effect, which triples the theoretical warming effect of adding CO2 based on lab experiments.
If that positive feedback theory was true, there would have been runaway global warming long ago, when the atmospheric CO2 level was much higher than today. Up to seven times higher, according to geologists. And none of us would have been alive today to discuss climate science!
Beyond that common sense argument, consider a 2020 study about CO2 that leads to the same conclusion about the runaway global warming theory.
That unproven water vapor positive feedback theory does serve a pupose. It is needed by climate alarmists to scare people about global warming.
Leftists (and other politicians too) know that scared people are easy to control, and will let them do what they want. What they want often involves new socialist policies that have nothing to do with energy use or the climate! Such as a large majority of the roughly $100 trillion spending proposed in the Green New Deal.
"The warming effects of CO2 and water vapor do not add; they oppose each other. This is opposite (of what the) IPCC claims.
The IPCC claims doubling CO2 from 280 ppm to 560 ppm over the course of several centuries produces a warming of 1.2°C on its own.
... Since this is not enough to induce catastrophic warming or propel CO2 mitigation policies, IPCC models suggest water vapor perpetually rises along with CO2 and warming, and this rising positive water vapor feedback drives this initial 1.2°C warming up to 3°C, 4°C, and beyond.