Booker short of the mark on greenhouse gas claims
Climate skeptic columnist Christopher Booker returns to a familiar theme this week, with an attack on measures designed to cut carbon dioxide emissions. This week’s instalment has an antipodean theme as he criticises legislation to charge carbon dioxide emitters in both the UK and Australia.
What sources does Booker pick to back his argument that carbon dioxide is an imaginary threat? Well, he chooses a book by Australian skeptic geologist and mining magnate, Ian Plimer.
But does Plimer’s work make a solid foundation for arguing that policies to cut carbon emissions are, as Aussie opposition leader Tony Abbott would say, “crap”?
Plimer’s book is rougishly titled ‘How to get expelled from school: a guide to climate change for pupils, parents and punters’, and suggests 101 questions for school children to ask their teachers about climate change, along with Plimer’s own answers.
The book has received poor reviews from climate scientists, and usefully, the Australian government’s Department of Climate Change and Energy Efficiency (DCCEE) actually bothered to provide answers to the questions posed in Plimer’s book based on up to date peer reviewed science.
Citing Plimer’s book, Booker gives a “vivid illustration of how great is the threat posed to the planet by man-made CO2”:
“If one imagines a length of the Earth’s atmosphere one kilometre long, 780 metres of this are made up of nitrogen, 210 are oxygen and 10 metres are water vapour (the largest greenhouse gas). Just 0.38 of a metre is carbon dioxide, to which human emissions contribute one millimetre. Australia’s share of this is 0.015 of a millimetre”
We guess that the implication here is that the relative proportion of carbon dioxide in the atmosphere is so small, it’s too small to change the climate.
Considering the analogy, it’s (roughly) right that 0.38 metres out of a kilometre would represent the proportion by volume of carbon dioxide in the atmosphere. Plimer and Booker are a little out of date, and you can find the most up to date atmospheric carbon dioxide measurements here.
The DCCEE says:
“The current global concentration of CO2 is around 390 ppm, which is 40 per cent higher than before industrialisation and well beyond the natural range of the last 800,000 years of between 172 and 300 ppm.”
In the analogy this would amount to about 0.39 metres.
Clearly Plimer and Booker intend this analogy to demonstrate how insignificant carbon dioxide is, with it making up only a small proportion of the atmosphere.
But the fact that carbon dioxide is only a small proportion of the atmosphere doesn’t mean it is insignificant in causing warming of the planet. Indeed, without any carbon dioxide in the atmosphere at all, we’d all be a lot colder, as DCCEE explains:
“The chemical properties of greenhouse gases, such as CO2, mean that they strongly absorb and re-emit infra-red radiation, which is felt as heat. This process maintains the Earth’s temperature at 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist. […] Over 99 per cent of the atmosphere is made up of oxygen and nitrogen, neither of which are greenhouse gases. CO2 is a greenhouse gas and has a significant effect on the climate despite being a small percentage of the atmosphere.”
For another analogy, (contained in this video), compare carbon dioxide levels in the atmosphere to alcohol levels in the blood. 0.04% blood alcohol – roughly equivalent to the amount of CO2 in the atmosphere, again – is a small amount, but it makes a difference.
The fact that carbon dioxide causes warming of the atmosphere can be demonstrated in the laboratory by basic experiments. Many different experiments have confirmed this, as have observations of current temperature trends.
Returning to the analogy, it’s not at all clear how Plimer reaches his claim that “just one millimetre” out of 0.38 metres of carbon dioxide in the kilometre of atmosphere would be down to man-made emissions.
In fact carbon moves through a natural cycle, being emitted and absorbed by natural processes. The carbon dioxide emitted from natural processes is absorbed via the land and ocean, leaving the overall natural carbon dioxide roughly in balance. Around 40% of the human produced carbon dioxide emissions are taken up by the land and ocean – the rest of the carbon dioxide that we put into the atmosphere is additional to this natural balance, and adds to what is already in the atmosphere.
DCCEE says:
“To claim that human emissions are small compared to natural emissions ignores the natural carbon cycle which keeps our climate in balance. Of the total amount of CO2 that is released into the atmosphere per year, human activities are responsible for approximately 3 per cent. As long as we keeping adding CO2 into the atmosphere faster than natural sinks can absorb it, CO2 levels will continue to rise and the Earth will continue to warm.”
Booker also subtly misleads about the relative importance of water vapour and carbon dioxide as greenhouse gases. Booker describes water vapour as “the largest greenhouse gas”, which is a usefully ambiguous term.
To clarify, water vapour is more effective at absorbing heat energy in the air than carbon dioxide. Booker seems to be implying that water vapour is a more important driver of climate than carbon dioxide. But water vapour is considered to act as a feedback, adding to the warming driven by increased levels of carbon dioxide and other greenhouse gases.
This is because water vapour is short-lived in the atmosphere, lasting only hours or days in the atmosphere before being rained or snowed out, so it does not accumulate in the atmosphere in the same way as the other greenhouse gases. In contrast, carbon dioxide can remain in the atmosphere from decades to tens of thousands of years.
The amount of water vapour that the atmosphere can hold increases as the atmosphere gets warmer. This means that the amount of warming water vapour can cause is related to the levels of other greenhouse gases in the air.
Yet again, Booker presents a confusing mix of bad arguments about the climate, using misleading analogies and material referenced from climate skeptics who have been thoroughly debunked to try and refute the basic physical facts of climate science.