The Gaia thermostat

Translating ideas

Journalists who cover developments in science have a tricky and highly-skilled job. They have to be able to grasp complex concepts in a range of different fields, and then express those concepts in language that the average lay reader can grasp. This is essentially a matter of translation - the journalist has to be able to decipher the complex technical terminology of scientific papers, and then express the key ideas and logic in Transferable Academic Language (TAL - see Language of Instruction ). At a more basic level, this is much the same as the task that our students have as they grapple with Biology or Chemistry, or indeed Economics or Geography.

Here is an example of good scientific journalism:

How it works : Gaia

If enough living creatures all do the same thing, they can affect a whole planet. No one warned the primitive bacteria in the first ages of the earth that they would change the atmosphere, but it is as well for us oxygen breathers that they did. Today, we in our turn seem to be changing it again.

Gaia theory goes a step further, suggesting that living things do not just change the environment, but control it. It envisages a web of links between air, oceans and climate that improves for living things, and which is driven by life itself. We do not know all the details, but it is becoming clearer how it might work.

One of the most convincing links is between tiny sea-borne plankton and global temperature. The plankton do not care about the planet; they are pursuing their own Darwinian ends. But the every-day business of survival causes them to make chemicals that affect the skies above the ocean.

Here's how: plankton need to keep their insides largely free of the salt in the water that surrounds them. They manage this by making chemicals, called betaines, which have separated positive and negative charges in the same molecule. This makes it easier for the cells to keep out the charged ions in sea water. The betaines used by the smallest so-called phyto-plankton use sulphur to carry the positive charge. When the phyto-plankton are eaten by larger organisms, this sulphur ends up as the gas dimethyl sulphoxide, or DMS. Some of this passes from ocean to air, where it produces tiny droplets of sulphuric acid. These attract more water vapour, thus aiding condensation. If there are enough of these droplets, they seed clouds. White clouds are better at bouncing the sun’s rays back into space than blue ocean, so they will cool things down below.

All we need now is a link between temperature and the rate at which the phyto- plankton do their chemistry and we have one mechanism for a planetary thermostat. Exactly how this would work is not yet clear, but there are several possibilities. It might be that warmth simply encourages growth; or that warmer air makes sea winds stronger, thus stirring up more food for plankton near the surface. And anything that increased the amount of salt in the ocean would encourage them to make more betaines.

The full answer will be more complicated. Some by-products of betaines seem to be used as a chemical defence against organisms that graze on plankton, so there will be more than one kind of control on production. And it looks as if only about 10% of the DMS in the water ever gets into the air, and it is not yet known what happens to the rest of it.

However, the general idea is a good example of how even the smallest organisms acting in concert, can influence something as far beyond their local concerns as the climate. And they can do it in a way which fits in perfectly well with their selfish interests as defined by natural selection. It makes Gaia less romantic, perhaps, but more real.

Jon Turney in The Guardian 27 January 2001


How it works: Gaia with the main basic text

Gaia flowchart    worksheet showing the main ideas graphically

Two further handouts identify Transferable Academic Language in Gaia - key verbs, modifiers, nouns



Ask the students to analyse the stucture of the text. This means, principally, looking at the function of each paragraph - "What is each paragraph there to do?" Such analysis will result in different answers, from the simple to the more acute:-

'Beginning, Middle & End' ... The text can be seen as an example of that tired cliché 'Introduction, Main Body, Conclusion' -

Introduction - paras 1 - 2

Main Body - paras 3 - 7

Conclusion - para 8

(If I had a euro for every time I have heard that all writing has those three sections! I know why teachers say this, but ... personally, I find it an rudimentary, even unhelpful concept - it simply substitutes a parroted oversimplification for serious thought about the individual structure of every text. )

'Chunk by chunk' ... a sub-divided version of the three-part analysis -

Introduction, Overall - paras 1-2

Introduction to key example - para 3

Main 1 - the basic theory - paras 4 - 5

Main 2 - possible extensions - para 6

Main 3 - objections - para 7

Conclusion, Overall - para 8

'Detailed' ... ask the students, in effect, to give a one-sentence summary of each paragraph, and then comment on how the argument is developed in detail, step by step.

Of course, this piece of professional journalism can be seen as of the same family as a student essay ... and if they can detect and analyse the fact that the various paragraphs have each a clear function, then they should plan their own work with that same sense of clear function.

Concept flow-chart

Focus the students' attention on the fourth paragraph. This is where the process of the central example is explained. You could simply ask for an oral summary of the process; or ask them if they can present the process, more concretely, in the form of a flow-chart.

Discuss how easily they can follow the logic of the explanation ... and if not, why not?

The more Advanced the students are, the more likely that they will be able to follow the quite dense line of argument. The more Basic they are, they more they may need the help of the Gaia Flowchart to guide their reading and their struggle with the concepts.

Use of metaphor / analogy

I feel the text is slightly flawed, because the useful analogy of the "planetary thermostat" is introduced too late, in line 26. I would have introduced it earlier, in line 11 :

"One of the most convincing links is between tiny sea-borne plankton and global temperature, functioning as a kind of planetary thermostat."

You could suggest this idea, and see what the students think - and then discuss the value of metaphors and analogies in aiding explanation. [ See more detailed comment on Handling analogy ]

The problem is that the effectiveness of this analogy depends on students knowing what a thermostat is! Which raises the following issue ...

Assumed knowledge

The journalist assumes a reader who is mature and relatively well-informed, and so doesn't feel that he has to explain about how the "...primitive bacteria in the first ages of the earth ... would change the atmosphere ...", nor why "... it is as well for us oxygen breathers that they did" (ll 2-4). I don't know precisely, but I can infer that bacteria produce oxygen as a by-product. Equally, I catch and understand the allusion to "Darwinian" (l.12) - but I have certainly met students who don't, so they will not fully understand the point about the bacteria not caring about the planet.

But does one need to know what all of the words mean to understand the general concept? You certainly do if you want to write an intelligent explanation, but you don't really if you are reading. I wouldn't recognise a plankton if I met one socially, and I've no idea what 'positive and negative charges' do to 'charged ions' - but these details don't matter in this case, because I can extract the overall idea of the process, like this :-

  • Plankton make chemicals which use sulphur.
  • When the plankton die, the sulphur passes into the ocean, then the air.
  • In the air, a form of this sulphur helps make clouds.
  • Clouds reflect the sun's light, so the more clouds there are, the cooler the world.

We should urge students to use their wits, and not be distracted by knowledge gaps - but rather to concentrate on grasping the key point. If they can focus the key point when they read, they are likely to be better at focusing the key point when they write.

TAL elements

Two further handouts - Gaia TAL - identify elements of Transferable Academic Language. Much of the economy and precision of the text relies on the skilful use of these useful items of vocabulary. The handouts identify (1) verbs, and (2) modifiers and nouns.

Notice that the various words identified are indeed highly transferable - they could be used in explanatory in a wide range of subjects and are not technical terms restricted to Ecology or Environmental Studies.

Do your students know what all of these words mean? Precisely? And if not, how do you teach this vocabulary?


Links & extensions

Presenting cause and effect... clear explanation depends on methodical thinking, and various pages in the site contain texts which demonstrate this -often in different ways, for different purposes... NOTE: the following list of links begins with 'explanations', and then leads into 'instructions' - the two modes of expression overlap, since both require accurate analysis leading to clear exposition...

How money works  ... a lucid explanation of the basic principle behind the idea of 'money'- i.e. symbols which in themselves have no value, but represent value ... Yuval Noah Harari at his skilful best... a toolkit of examples of how to explain clearly...

Containers  ... careful and methodical explanation of how containers have contributed to the development of a global economy... complex analysis and presentation of causes and effects... stimulates thoughts about everyday objects which are taken for granted...

Bricks ... a direct and clear explanation of tricks performed by a chinese acrobatic theatre troupe - deceptively simple, because when youthink about what is explain, the tricks appear impossible... emphasises methodical sequence...

Step by step Explanation ... Sherlock Holmes explaining why something is 'elementary' - a model demonstration of logical connections between observations and interpretations...

Model instructions ... an example of student work, handling an exam task about giving instructions about how to carry out an operation on a computer... contains a detailed analysis of how to set about getting your ideas organised...

Instructions 1 ... an entertaining exercise which involves giving instructions about how to make a paper plane... remembering that 'giving instructions' is closely linked to 'explanations' - both involve a sound grasp of causal effects, but 'explanations' apply to what has happened, and 'instructions' apply to what should happen...


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