[Bored Wombat]

Thanks for your post BriGuyPI. It's good to see some new blood here.

Originally Posted by BriGuyPI

I think there is like 5,000 Trillion tons of atmosphere

Actually, a bit more than that ... 5,660 trillion tons. (It's close to 5,000 trillion tonnes).

and CO2 is 0.038% of it

This value is by volume. The value is about 0.058% by mass.

so that is 190 Trillion tons of CO2 in our atmosphere.

You've multiplied by 0.038 and have forgotten that it is 0.038%, so you should have multiplied byt 0.00038, giving 1.9 trillion tons. Using the more correct values of 5.66 trillion x 0.00058 gives about 3.3 trillion tons of atmospheric CO2

Now it is said in here that we have added 1100 Billion or 1.1 Trillion tons of CO2.

That's looks about right, if you mean the amount by which human activities have increased the atmospheric CO2 concentration to date. Actual emissions are a little less than twice this, but not all of it has remained in the atmosphere. The oceans have dissolved some. (Increasing their acidity and becoming more hostile to oceanic calcifying organisms ... but I digress.)

So 1.1 Trillion divided by 190 Trillion is roughly 0.5% we have added since the start.

Using the correct figures, 1.1 trillion divided by 3.3 trillion is about 33.3% we have added since the start.

This is too simple for most people to grasp. Whoever quoted the 1100 Billion has a good estimate based on estimates from current output; and estimating the amount we have put out and are putting out, is not too hard. So can someone now explain how .5 % added to a GHG that is only a very minor one next to water vapour, could be responsible for warming the planet?

It's good to see that you are thinking with your head and not parroting a line from a denialist website. I hope that I don't seem to forward in correcting your arithmetic, and I certainly agree that your thinking is sound ... a 0.5% increase would be insignificant.

However the 50% increase in atmospheric CO2 has been noted from ice cores, and the part that has occurred since the late 50s has been directly measured:


The total natural greenhouse effect on earth is about 30 celsius degrees, so a 50% increase in that would result in about 15 further degrees of warming, so the IPCC's view that a doubling of CO2 will result in a warming likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values. is quite believable.