Of course, if we kept up the exchange long enough, Boss, like any other 'Conservative' would resort to lying, or demonstrating his vast ignorance. Since we started burning fossil fuels, the CO2 in the atmosphere has gone from 280 ppm to over 400 ppm. The highest level we saw from natural sources in the last million years or more was 300 ppm in the Eemian. And that addition of 20 ppm at that time resulted in sea levels about 20 feet higher than today. The sea level for our descendants is going to be far higher than that. In fact, we have not seen GHG levels as high as they are today for over 4 million years. And the world was a far different place then than today. The rate at which we are changing the climate will not give either the natural biosphere a chance to adjust, nor the agriculture we all depend on.poison: a substance with an inherent property that tends to destroy life or impair health.
www.dictionary.com
Carbon dioxide (CO2) is a toxic gas at high concentration, as well as an asphyxiant gas (due to reduction in oxygen). Irritation of the eyes, nose and throat occurs only at high concentrations. The concentration thresholds for health effects are outlined in the table.
Exposure limits
(% in air) - - - - - -Health Effects
2-3 - - - - - Unnoticed at rest, but on exertion there may be marked shortness of breath
3 - - - - - Breathing becomes noticeably deeper and more frequent at rest
3-5 - - - - - Breathing rhythm accelerates. Repeated exposure provokes headaches
5 - - - - - Breathing becomes extremely laboured, headaches, sweating and bounding pulse
7.5 - - - - - Rapid breathing, increased heart rate, headaches, sweating, dizziness, shortness of breath, muscular weakness, loss of mental abilities, drowsiness, and ringing in the ears
8-15 - - - - Headache, vertigo, vomiting, loss of consciousness and possibly death if the patient is not immediately given oxygen
10 - - - - - Respiratory distress develops rapidly with loss of consciousness in 10-15 minutes
15 - - - - - Lethal concentration, exposure to levels above this are intolerable
25+ - - - - - Convulsions occur and rapid loss of consciousness ensues after a few breaths. Death will occur if level is maintained.
Carbon Dioxide (CO2)
Okay... time for your math lesson. Let's take the lowest figure in your scale for CO2 to have ANY sort of physical impact on humans... 2%. This translates to 20,000 ppm. At 400 ppm, I think we're safe. Even OSHA regulations allow human exposure to as much as 6,000 ppm.
Also, when we compare the amount of CO2 man produces through burning of fossil fuels with natural sources of CO2, we find that nature produces about 97% to man's 3%. Of course, in fairness, that 97% does include man's natural emissions from breathing as well as other mammals. We can also look at other much more toxic gases, such as methane and carbon monoxide... Again, we find that those far outweigh the relatively small amount of CO2 produced by man's burning of fossil fuels. Cattle alone produce about 1,000% more methane than man produces CO2 through industrialization, and methane is far more dangerous.
But you are really stretching it to consider CO2 toxic. Indeed, anything is toxic to humans in pure concentration, even oxygen.
Why would the earth look the same under naturally high CO2 as it does now under unnaturally high CO2 caused by fossil fuel use?