Could CO2 be a cooling gas?

Posted on 25 April 2017 by Scottish-Sceptic

We all know that according to basic science CO2 is supposed to warm the globe. And based solely on its radiative properties I would agree.
However… I horrible thought crossed my mind the other day.
Anyone who has been reading my blog will know about the effect of pollutants like SO2 which seem to in some way affect cloud droplet formation (they cause more clouds that can have a cooling or warming effect depending on their height and other factors).
It’s also well known it produces acid according to the following equation:

SO2 + H2O + 1/2 O2 → H2SO4 ⇌ H+ + HSO4–

But doesn’t CO2 behave very similarly to produce an acid in water:

CO2 + H2O ⇌ H2CO3 ⇌ HCO3− + H+

But what if the critical component in cloud nucleation was the H+? In other words both SO2 and CO2 could BOTH promote cloud formation (although CO2 being a much weaker acid would have a much reduced effect).
As such there is a possibility that marginal increased levels of CO2 could REDUCE GLOBAL TEMPERATURE (in the presence of an atmosphere with water-droplet formation).
 

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3 Responses to Could CO2 be a cooling gas?

  1. David Cooper says:
    25 April 2017 at 19:40

    Hi S.S., love the honesty in these blogs! Forgive my interruption, but I have a proposal which will probably improve your case involving Hydrogen ions.
    I doubt very much if H2SO4 (sulphurIC acid) can be produced from SO2 under normal atmospheric conditions. The industrial process first uses 500 oC, a catalyst and a pressure above atmospheric. Moreover, less than 1% of H2CO3 will produce hydrogen ions but almost 100% of sulphuric acid (H2SO4) will give hydrogen ions – H+.
    Safer to compare carbonic acid with sulphurOUS acid.
    When SO2 gas reacts with water sulphurous acid results:
    H2O + SO2 —> H2SO3, quite similar to:
    H2O + CO2 —> H2CO3.
    Followed by:
    H2SO3 —> H+ + HSO3- About 10% of sulphurous acid converts to H+.
    As you point out, carbonic is a weak acid but like sulphurous acid it will deliver significant amounts of hydrogen ions.
    [My information comes from a list of Acid Dissociation Constants and my knowledge as a retired A level Chemistry teacher]

  2. oldbrew says:
    25 April 2017 at 21:21

    Could CO2 be a cooling gas? – in the right circumstances, yes…
    Carbon Dioxide (CO2) Fire Extinguisher
    http://www.safefiredirect.co.uk/Page/32/carbon-dioxide-(co2)-fire-extinguisher.aspx
    But in the atmosphere, also possible as it must radiate in all directions i.e. including away from the Earth and towards outer space.

  3. Scottish-Sceptic says:
    25 April 2017 at 22:10

    Thanks – the line of reasoning follows that if radiation causing ionisation can create clouds in a cloud chamber, then perhaps chemically creating ions in a vapour may have the same effect.
    However, if my knowledge of chemicals in solution is patchy – my knowledge of how molecules of CO2 and CO2/SO2 interact and whether they can create ionisation in some form is (almost) none existent.

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