No... We don't have to worry about human health risks until CO2 reaches levels 500 times greater than current levels. The 'millionaire' analogy was given to illustrate how small and insignificant CO2 is in our atmosphere, to idiot dolts like Onzies, who thinks it is a harmful pollutant.
It appears you are wrong on the OSHA standards.
Due to the health risks associated with carbon dioxide exposure, the U.S. Occupational Safety and Health Administration says that average exposure for healthy adults during an eight-hour work day should not exceed 5,000 ppm (0.5%). The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues is significantly less. For short-term (under ten minutes) exposure, the U.S. National Institute for Occupational Safety and Health (NIOSH) and American Conference of Government Industrial Hygienists (ACGIH) limit is 30,000 ppm (3%). NIOSH also states that carbon dioxide concentrations exceeding 4% are immediately dangerous to life and health[48] although physiological experiments show that such levels can be tolerated for some time [49].
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5% would be under 150 times current levels. That is what it is safe to work in for eight hours. OSHA does not mean that that would be fine for our environment. The greenhouse effect does not happen in a mine shaft.
Plants WOULD thrive in a desert with higher CO2 concentrations, because it would let them retain more moisture. And most greenhouses I've been in, are considerably warmer than what I find comfortable... but then, we invented air conditioning because that can often be the case outside of a greenhouse. CO2 levels in the atmosphere have nothing to do with drought or the ocean. We've had approximately the same amount of CO2 in the atmosphere for as long as man has roamed the Earth. Before man, there was a much higher concentration of CO2 in the atmosphere, and this is the environment most plants evolved in. These early high concentrations of CO2 in the atmosphere, certainly didn't destroy the oceans or cause massive droughts, otherwise, we wouldn't be here right now.
MOST modern plants, including food crops, do not do well in extreme heat. The droughts will deprive them of moisture. The high CO2 concentrations will lead to acidity in the oceans and could have negative effects on sea life.
Yes, animals and plants once lived in environments with higher Co2 concentrations (it was no where near 500 times today's levels and was significantly lower than the OSHA guidelines). They were not today's animals and plants. Further, they had time to adapt to that then new environment and thrive. Rapid change will not be good for most living things. Something will survive and possibly thrive. It might not be us.
No, water vapor doesn't "follow" carbon dioxide, it is present no matter if there is CO2 in the atmosphere or not. Approximately 94% of the "greenhouse gases" is water vapor, carbon dioxide makes up less than 5%. Regardless of what we do about CO2, we still have all that water vapor, causing a greenhouse effect. If we ever eliminated the greenhouse effect, all life on Earth would vanish, the oceans would dry up, and our planet would become like Venus. I think I like it better the way it is now!
Co2 and methane have the greatest influence on the thermal structure of the atmosphere. Water vapor varies in relation to that and therefore water vapor follows co2.