Friday, February 5

Some basic facts about Carbon Dioxide

The recent poll about changing public opinion about climate change is somewhat alarming, but not surprising considering the continued attacks on scientists and the research they conduct, combined with the recent Northern hemisphere cold spell (the Southern hemisphere is piping hot, when we are in our Northern hemisphere winter)

The problem of course is that many people on the margins of being convinced one way or another are going to be switching views as the evidence changes, especially if their knowledge of science is limited.

Even the most basic truths in science are questioned by some. Typical views held are that the amount of Carbon Dioxide in the atmosphere is tiny, it is food for plants, or it doesn't cause warming.

Well the comment about 'food for plants' is effectively a PR and marketing comment. The sort of thing used by companies to emphasise the positive aspects of a product that might have some more damaging aspects

The other two issues are of more interest as far as climate goes. Carbon Dioxide consists of a molecule containing 3 atoms and in this respect differs from Oxygen and Nitrogen, the two most abundant gases in the atmosphere. Oxygen consists of a pair of oxygen atoms, whilst Nitrogen consists of a pair of Nitrogen atoms.

What is the relevance of molecules having two or three atoms?
Combined with other qualities of the CO2 molecule, a lot as it happens. Carbon Dioxide has the ability to absorb infra red radiation emitted by the ground, whilst Oxygen is more likely to absorb energy at higher frequencies, outside the infra red bandwidth.

The details of what happens in a Carbon Dioxide atom when it is hit by a Photon are complicated. However, simply put, both Oxygen atoms are set into a vibration motion in relation to the Carbon atom. These 'bond' vibrations mainly occur when hit by radiation of a specific frequency bandwidth, namely the infra red band. Hence the vibrations represent an absorption of energy. Such behaviour can be observed using spectroscopy instruments.

This significantly changes the importance of the different atmospheric gases in the climate change issue, because although Oxygen and Nitrogen are very abundant in the atmosphere (78% and 21% respectively compared to Carbon Dioxide at 0.039%), they aren't going to directly absorb infra red radiation. This places Carbon Dioxide and other greenhouse gases, higher up in the importance table. So making a comment like 'carbon dioxide is a trace gas' would be rather foolish and ignorant.

So where does this leave Carbon Dioxide?
After water vapour, CO2 (Carbon Dioxide) is the next most abundant warming gas in our atmosphere and hence is very important in any analysis of climate. In fact without Carbon Dioxide or water vapour, the Earths climate would be significantly different and largely cooler.

Water vapour? I hear you say.
Yes, even someone like me recognises that water vapour is a greenhouse gas. However it's interaction in the atmosphere and the greater ecosystem are complex. Water is a dynamic molecule at Earth temperatures, changing between gas, liquid and solid easily, where as Carbon Dioxide does not change state that much in our atmosphere. Hence CO2 is likely to have an impact on the dynamics of water, rather than the other way around. Water will change it's affect on climate with inputs of warming from other greenhouse gases, including Carbon Dioxide, Methane and Nitrous Oxide. This is called a feedback mechanism, it so happens that water has both positive and negative feedback impacts on our climate because of this mechanism.

I think I'll stop before I ramble on any more about water vapour and other issues! I'll probably post some more about other climate science issues later.

More Climate Science


Anonymous said...

You might like 'The Gaia Hypothesis' by James Lovelock. I read it during my degree. (unfortunatly I lent my copy to someone and never got it back!) I totally agree your point about how ill educated the public are on the subject.

During the 'snow week' I was infuriated by all the news reporters asking the average Joe on the streets about the global warming/climate change 'myth' as one guy put it, using the word 'obviously' alot!

Anonymous said...

All true - but the key to whether the CO2 increases we are seeing will lead to a 'significant' increase in temperature are the feedback mechanisms and these are much less understood.

TheVille said...

Re: Anonymous (No. 2)

Climate sensitivities are well known and have been calculated many times by many different scientists. Such calculations go back to Arrenhius who used CO2 and water vapour to make the first estimate in the 19th century. Today scientists take into account water vapour, cloud properties, ice albedo etc.
Importantly all calculations show the calculated lower limits of sensitivity are above the sensitivity calculations shown by doubling CO2 alone. This isn't surprising since you have a net energy gain in the system, this provides the mechanism for a net positive (warming) feedback in the system as a whole, which swamps any negative (cooling) feedbacks.

There are also plenty of observations today showing feedback mechanisms engaging with the climate system as one would expect.