Again, they're referring to the 400 parts per 1,000,000 ratios. That's a 0.04 percent concentration (4 hundredths of 1 percent).
CO2 levels in outdoor air typically range from 300 to 400 ppm (0.03% to 0.04%) but
can be as high as 600-900 ppm in metropolitan areas. CO2 is produced by body metabolism and is a normal component of exhaled breath. It also results from the burning of fossil fuels and natural sources such as volcanic eruptions and forest fires.
OSHA (Occupational Safety and Health Administration has established a PEL (Permissible Exposure Limit) of 5,000 ppm which is (0.5%) 1/2 of 1 percent for an 8-hour work exposure period. That's 12.5 times the 400 ppm.
10,000 ppm (1%) typically has no effects except for a few cases of possible drowsiness.
15,000 ppm can cause some mild respiratory responses in some people.
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While I agree that more people equal a larger carbon dioxide production, we can't control volcanos, forest fires, and other disasters. Until more people buy into the notion that EVs will help in a positive way, it will take time before the fossil-fueled vehicles are phased out, if ever.
What I don't cater to is every politician exclaiming that the Sky is Falling like Chicken Little, with regard to some Global Warming notion. Sure, more people equal more CO2 being released. Do you want more Oxygen? Tell those nutjobs to quit with the deforestation of jungles and tree resources everywhere on the planet! Yes, some plants do not take in as much CO2 as we originally thought but they do still require it to live.
Trees take in CO2 and release O2. Makes sense. Wind, Water, and Solar generation are great resources for sure but the use of fossil fuels is not ever going completely away. Diminish yes, but disappear...no.
I'm just trying to show that this 400 ppm statement of extreme worry is of some concern but not worth losing sight of the facts. Perhaps an early warning is the only thing that will wake up some people to the potential of doing nothing but we're not going to stop it all at once and the Earth and Sun are going to continue to do what they've been doing for eons. The cyclic nature of warming and cooling will go on no matter which side of the fence one happens to be on.
