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>> anthropogenic warming is down to the direct heating effect of CO2... OK, let's say this was the case. First question - what percentage of CO2 in the atmosph

>> anthropogenic warming is down to the direct heating effect of CO2... OK, let's say this was the case. First question - what percentage of CO2 in the atmosphere is attributed to human activity?

Brakenshire 9y ago
We've increased it by about 50% since the industrial revolution, from about 280ppm to 410ppm. You can tell both from isotope analysis and inventory studies most of the ongoing excess is down to humans. Also, I'm not sure what in that statement is even up for debate, does anyone question that a concentration of CO2 in a volume of space absorbs light at particular wavelengths? It's core science, and a straightforward calculation.
- ChemicalWarfare 9y ago
  That's not what I asked. If total CO2 in the atmosphere is 100%, what portion of that number is attributed to human activity? Also, CO2 itself - out of all of the greenhouse gases in the atmosphere - what percentage belongs to CO2?
  - mikeash 9y ago
    How is that not what you asked? If we've increased the amount by 50% over preindustrial levels, then the current portion attributable to us is about 33%.
    - ChemicalWarfare 9y ago
      ...except that figure is less than 4%. about 8 gigatons are attributed to humans out of ~220 gigatons injected into the atmosphere overall on a yearly basis. the kicker is - the percentage of CO2 in the overall greenhouse pool is also in the single digits, the most significant (volume-wise) greenhouse gas which comprises about 95% of the greenhouse gases in the atmosphere is water vapor. so if you factor that in - if humanity ceases to exist tomorrow, there is a potential for a .3% change in greenhouse gas volumes.
      - Brakenshire 9y ago
        > ...except that figure is less than 4%. about 8 gigatons are attributed to humans out of ~220 gigatons injected into the atmosphere overall on a yearly basis. This is like the difference between profit and savings. Accumulated CO2 is a savings accounts, and the pre-industrial climate in the short term acts like a business which has zero profit, balanced revenues and expenditure. If you come into the business, and hold expenditure the same, but increase revenues by 4%, and yield a 4% profit, which every year you put in the bank account, that is going to accumulate over time. And the warming is created by the accumulation. You talk about a 4% yearly excess as if that was a small amount! Also, your point about water vapour ties into what I said in the earlier comment, a lot of the warming is exactly that secondary effect - CO2 has a direct heating effect, that raises temperature, which then raises the partial pressure of water vapour, which increases concentrations of water vapour in the atmosphere, which as you say is a very important greenhouse gas. It's the combination of these two effects, of direct CO2 warming, causing increased water vapour concentration, which accounts for the baseline warming which everyone who is sceptical of computer models should believe in. This very well-established baseline warming accounts for about half of the climate sensitivity proposed by the IPCC, if you think computer models are junk, that discounts many of the positive feedbacks proposed, but also the negative feedbacks which would have to exist, to lead to zero warming.
        ChemicalWarfare 9y ago
        >> You talk about a 4% yearly excess as if that was a small amount! This analogy would only make sense if somehow this 4% wasn't spent or was spent differently than the rest of the money. Also don't forget we're talking .3% if you take all of the greenhouse gases into consideration. >>...if you think computer models are junk, that discounts many of the positive feedbacks proposed, but also the negative feedbacks which would have to exist, to lead to zero warming. This sounds like mental gymnastics trying to single out the evuuhl CO2. Given the fact that planet Earth went through multiple heating/cooling cycles way more severe than the current warming trend without any antropogenic influence, applying Occam's razor here would lead me to believe the issue lies elsewhere.
      - mikeash 9y ago

>> anthropogenic warming is down to the direct heating effect of CO2... OK, let's say this was the case. First question - what percentage of CO2 in the atmosphere is attributed to human activity?

Brakenshire 9y ago

We've increased it by about 50% since the industrial revolution, from about 280ppm to 410ppm. You can tell both from isotope analysis and inventory studies most of the ongoing excess is down to humans. Also, I'm not sure what in that statement is even up for debate, does anyone question that a concentration of CO2 in a volume of space absorbs light at particular wavelengths? It's core science, and a straightforward calculation.

ChemicalWarfare 9y ago
That's not what I asked. If total CO2 in the atmosphere is 100%, what portion of that number is attributed to human activity? Also, CO2 itself - out of all of the greenhouse gases in the atmosphere - what percentage belongs to CO2?
- mikeash 9y ago
  How is that not what you asked? If we've increased the amount by 50% over preindustrial levels, then the current portion attributable to us is about 33%.
  - ChemicalWarfare 9y ago
    ...except that figure is less than 4%. about 8 gigatons are attributed to humans out of ~220 gigatons injected into the atmosphere overall on a yearly basis. the kicker is - the percentage of CO2 in the overall greenhouse pool is also in the single digits, the most significant (volume-wise) greenhouse gas which comprises about 95% of the greenhouse gases in the atmosphere is water vapor. so if you factor that in - if humanity ceases to exist tomorrow, there is a potential for a .3% change in greenhouse gas volumes.
    - Brakenshire 9y ago
      > ...except that figure is less than 4%. about 8 gigatons are attributed to humans out of ~220 gigatons injected into the atmosphere overall on a yearly basis. This is like the difference between profit and savings. Accumulated CO2 is a savings accounts, and the pre-industrial climate in the short term acts like a business which has zero profit, balanced revenues and expenditure. If you come into the business, and hold expenditure the same, but increase revenues by 4%, and yield a 4% profit, which every year you put in the bank account, that is going to accumulate over time. And the warming is created by the accumulation. You talk about a 4% yearly excess as if that was a small amount! Also, your point about water vapour ties into what I said in the earlier comment, a lot of the warming is exactly that secondary effect - CO2 has a direct heating effect, that raises temperature, which then raises the partial pressure of water vapour, which increases concentrations of water vapour in the atmosphere, which as you say is a very important greenhouse gas. It's the combination of these two effects, of direct CO2 warming, causing increased water vapour concentration, which accounts for the baseline warming which everyone who is sceptical of computer models should believe in. This very well-established baseline warming accounts for about half of the climate sensitivity proposed by the IPCC, if you think computer models are junk, that discounts many of the positive feedbacks proposed, but also the negative feedbacks which would have to exist, to lead to zero warming.
      - ChemicalWarfare 9y ago
        >> You talk about a 4% yearly excess as if that was a small amount! This analogy would only make sense if somehow this 4% wasn't spent or was spent differently than the rest of the money. Also don't forget we're talking .3% if you take all of the greenhouse gases into consideration. >>...if you think computer models are junk, that discounts many of the positive feedbacks proposed, but also the negative feedbacks which would have to exist, to lead to zero warming. This sounds like mental gymnastics trying to single out the evuuhl CO2. Given the fact that planet Earth went through multiple heating/cooling cycles way more severe than the current warming trend without any antropogenic influence, applying Occam's razor here would lead me to believe the issue lies elsewhere.
    - mikeash 9y ago