Apples and oranges. If your analogy were meaningful, which it isn't primarily since you are using a toxic substance in place of a non-toxic substance, you are basically imposing a fallacy. Implying that CO2 is poison is disingenuous at the least and manipulative at it's worst.
Do you know that organic greenhouses enhance the CO2 levels to around 2000 ppm to increase production? CO2 is essential for life, it is not toxic. It is a clear (some gases have color), it is transparent and has no reflectivity. I spent years doing gas analysis, these are known conditions determined by over a century of science. Read OSHA standards for permissible CO2 levels in the workplace. Again. a in my working life I measured CO2 concentrations in enclosed spaces. OSHA limits workers to 8 hours a day in concentrations of 10,000 ppm.
Bottom line, 400 ppm CO2 is not hazardous, in fact the science of botany has determined this arbitrary number is precariously low regarding the ability of plant life to sustain itself.
Another fallacy is the idea of an average temperature of earth. I live on 10 acres, on one 1500 foot long side it is open, on the opposite side it is open with a small drainage coming from higher elevation. I have measured a 15 degree F difference from one side to the other in the mornings as cool air drops down the drainage, and the opposite side warms from sunlight. I have 100 foot gain in elevation from one end to the other, temperatures vary 1.5-2.8 degrees from top to bottom. As the sun rises, these variables change by the second. Temperatures at ground level in the forested areas can be 20 degrees cooler than the exposed areas. Cloud cover impacts temperatures, precipitation affects temperatures, prevailing winds affect the temperatures. Trying to model the average temperature in a 24 hour period on this ten acres is virtually impossible, averaging the temperature over 365 days even more so. If I go to another 10 acre parcel 1/2 mile from my house, it is shaded from sunlight on a hillside year round, and never attains the temperatures measured on my property. Extrapolate this out to the "average temperature of the earth", which is supposedly 58 degrees and it is a meaningless number. There are vast places on earth that never warm to 58 degrees, there are vast expanses that never cool to 58 degrees. What good is it to say the average temperature of the earth has increase 1/10th of a degree over 20, 30 or 50 years. Temperature is cyclical, and it is not uniform.