Serious arithmetic problem
"only about a1% concentration of CO2 is enough to cause serious health problems"
The site says: "Symptoms may begin to occur, such as feeling hot and clammy, lack of attention to details, fatigue, anxiety, clumsiness and loss of energy, which is commonly first noticed as a weakness in the knees (jelly legs)." for 1%. Serious health problems? Symptoms are like having 2 pints of beer in half an hour.
Current CO2 levels are "officially" at about 390 ppm; much, much less than the 10,000 ppm that is 1%.
Venus is hot at the surface in part because the pressure at the surface of the planet is about 90 times that of what we have on our planet. At the altitude where the pressure is about 1 Bar - one Earth atmosphere, Venus' atmosphere is only slightly warmer than Earth. The rest of the temperature difference is due to proximity to the sun and very slow, retrograde rotation of the planet - it turns, very, very slowly - backwards wrt other planets, with its "day" longer than its year.
The "greenhouse effect" has no foundation in fact. Heat is not "trapped". CO2 doesn't form a "blanket" or a barrier to outbound radiation.
Although CO2 absorbs IR radiation, it re-radiates it very quivckly at altitude, and below about 6000 metres above the surface, the incoming IR transforms morereadily to kinetic temperature; which can transfer to surrounding molecules of vastly more O2 and N2. CO2's rate of expansion with heating is greater than that of the rest of dry air, so its bouyant action encourages natural convection, increasing the rate of heat transfer.
The higher density of CO2 compared to the rest of dry air tends to concentrate the trace of gas that is CO2 to near the surface; i.e. where it's absorbtion properties tend to promote convection and convective cooling of the surface by displaced ("falling", cold) air coming in contact with the warm surface. One would be able to observe that effect in the real world were the concentrations of the gas not so small that any attempt to measure it is lost in the noise of measurement.