Hi, BarackZero.
Can I point out that the average human mass sits somewhere between 75-85 kg (75,000-85,000 g) and contains, on average, about 0.05 grams of iodine.
If you take 0.05 g of iodine and divide it by 75,000 grams of body mass, we see that iodine makes up about 1/1,500,000th of the human body mass, or 0.000000667 (6.67E-7) % of the human body mass.
Yet, curiously enough, look what happens when humans fail to get that 0.05 g of iodine:
Goiter.
For comparison, take your numbers: take 370 ppm (CO2 in the atmosphere), multiply it by 0.034 (% of atmospheric CO2 that is anthropogenic), and divide by 1 million (for the "parts per million"), and you discover that anthropogenic carbon is 0.000126 (1.26E-5) % of the atmosphere (which is low, because this percentage is based on particles, not on mass, as my calculations above are; and CO2 weighs more than the other molecules you mention).
If a difference of 6.67E-7 % in the human body can cause goiter, what makes you think a difference of 1.26E-5 %* in the atmosphere can't also cause big problems?
If it might cause problems, what exactly do you have against Al Gore wanting to fix it?
Edited by Bluejay, : "CO2" instead of "C" and the "and CO2 weighs more..." part added
-Bluejay (a.k.a. Mantis, Thylacosmilus)
Darwin loves you.