Goldilocks and the daisy?

Unfortunately scientist can slip into using cliches.  This is despite the fact that imagination and creativity are probably the key skills to successful science.  A quick Google Scholar search on the term ‘Goldilocks’ reveals over 24,000 scientific papers and books that use the term and only a small number of them involve three bears!  It has become shorthand for ‘just right’.  Understanding planetary temperatures is no exception.  Planet Earth is said to be located in the Goldilocks Zone of the solar system – not too far from the sun to be too cold, not to close to be too hot.  In practice, ‘just right’ conditions have prevailed throughout much of the 4.6 billion years of Earth history, the big question is why?

Just right: not too hot, not to cold

The probability of the Earth’s temperature remaining at suitable level for life to survive during much of the 4.6 billion years of Earth history has been described as a kin ‘to crossing a motorway blindfold during rush hour’.  When the Earth was first formed the solar constant, that is the amount of radiation received by the Earth from the sun, was lower than it is today.  The sun was dimmer and has been slowly warming ever since.  The solar constant has risen throughout Earth history but the average planetary temperature has remained broadly the same give or take a few wobbles.  The climate and the chemical properties of the Earth now and throughout its history seem always to have been optimal for life The question is why and how?

This observation led Professor James Lovelock to the radical conclusion that the Earth could regulate its own temperature just like any warm blooded animal.  He postulating thermo-regulation and coined the term Gaia – Goddess Earth – and suggested that the Earth was living.  In this context a living being is something able to regulate and optimise its environmental conditions.  He knew how to sell a story and the Gaia hypothesis was born.

Whether the Earth can truly be described as ‘living’ is largely irrelevant, the crux of the issue is that positive and negative feedback loops within planetary systems may operate against extremes just like the human body.  To hot and you begin to sweat, to cold and your body develops gooseflesh and a shiver.  The search was on to find self-regulating planetary systems and a number of such systems have emerged over the years.

One of the first of these was the role of dimethyl sulphide in cloud formation.  For condensation to occur you need condensation nuclei, tiny particles of dust or particulate matter around which water vapour can condense.  It is where ideas of cloud seeding in drought stricken areas come from.  Lovelock and his colleagues were able to demonstrate that a key condensation-nuclei was sulphur dioxide derived from dimethyl sulphide from plankton on the ocean surface.  As a result they found a large planetary feedback mechanism (Fig. 1).  The so called CLAW hypothesis was named after the authors involved in its discovery Charlson, Lovelock, Andrea and Warren (1987).

clawFigure 1: The CLAW hypothesis. (Source: Plumbago-Own work, CC BY 2.5,

The sun acts to increase the growth rates of phytoplankton due either to increased surface temperature and/or increased availability of sunlight. Certain phytoplankton, such as coccolithophorids, synthesise dimethylsulphoniopropionate (DMSP), and their enhanced growth increases production.  As this breaks down dimethyl sulphide (DMS) is produced first in seawater, and then in the atmosphere. DMS is oxidised in the atmosphere to form sulphur dioxide an important condensation nuclei.  The water content of clouds increases as a result increasing their reflectivity to incoming solar radiation (enhanced albedo).  The result is less solar heating of the ocean surface and a decrease in phytoplankton production of DMS resulting in a self-regulatory system.

Scientific modelling

Geographical research is not all about direct observations and fieldwork; there is more to geography than standing in the rain measuring things.  Physical and laboratory based experiments all play a part as does modelling.  Modelling involves the conceptual or numerical simulation of a series of processes that give rise to something like a landform or ecological species distribution.  Modelling is a central to our understanding of many geographical phenomena; it lies at the heart of the weather forecast on your smart phone or TV.

There is a range of different opinions as to what actually constitutes a ‘model’ but the simplest way of looking at it as any construct which generates a prediction. It follows that modelling, like experimentation and observation, is simply an activity that enables theories to be tested and examined critically.  Here are a just a few different types of geographical model:

  • Conceptual models. These are theoretic expressions, often in cartoon form, of the key variables involved in a particular process.  They are designed to scope, inform, communicate and help the reader frame ideas for testing.  Figure 2 is a conceptual model.
  • Physical models. Flumes and wave machines are used sometimes to test coastal or flood defences.  Here reality is scaled down and observed in microcosm.
  • Empirical/statistical models. These are based on observed data and attempt to look for causal relationships between several variables.  Lots of data is collected and statistics are used to pull out salient points or relationships.
  • Numerical models. We can use physics and maths to create a set of equations which describe elements of a process.  For example, we can describe soil strength or the rate of glacier flow via simple equations.  These types of models can vary along a continuum from those that are specifically grounded in a time and place to those that are more abstract.  If we ground and parameterise these equations with data from a specific place or time we can attempt to model and thereby reconstruct (or predict) phenomena at a different time.  For example, we might try to create a model of an ice sheet that once covered Britain and vary the input parameters to see how it behaves.  The experiment here is to find the input parameters that best recreate what we think happened in the past.  Alternatively we may create a predictive model such as a general circulation model (GCM) of the Earth’s atmospheric systems and their interaction with land and sea in order to forecast the weather.  The predictions made by the model become the test of its accuracy.  At the other end of the continuum are more abstract models that are not grounded in a specific place and time but allow us to explore more theoretical relationships between the variables involved.
  • Agent based models. This type of model is a form of numerical model which empower individual elements with the power to make decisions.  Imaging a large crowded stadium and someone needlessly shouts ‘bomb’.  Each member of the crowd is capable of make its own decision; to you run left, right or duck.  Perhaps less dramatic is to think of a herd of wildebeest migrating on the Serengeti; in theory each animal can make a choice as to the route it will follow, although it may be highly influenced by other members of the herd.  We can simulate this numerically by giving each agent in the model an individual decision making capacity according to a set of pre-set rules and step back and observe.  There are lots of ecological and geographical systems that lend themselves to this type of modelling.


Modelling has played an important role in the debate about Gaia.

Lovelock and colleagues developed a conceptual model of a self-regulating world, known as Daisy world.  They were not modelling the Earth specifically simply illustrating how self-regulation might work.

diamodelFigure 2: Conceptual illustration of daisy world.  Think about the distribution of daises and why they occur where they do.


Daisy world is a very elegant model (Fig. 2).  To start with they imagine a world inhabited by just two types of daisy – black and white ones – warmed by a sun similar to our own that starts cold and gradually warms up.  Now at first the planet is cold and black daisies thrive since their black pigmentation allows them to absorb more radiation than their white counter parts which tends to reflect solar radiation (i.e. white daisies have a higher surface albedo or reflectance).  The planet is warmer than one might expect, but as the solar constant rises the black daisies begin to be scorched by the sun.  Progressively white daisies thrive, since they can reflect some of the excess heat and keep the planet cooler.  Planetary temperature is moderated in this way as the solar constant changes over time.  It is an elegant illustration of a thermal regulation without any teleological need (i.e. need for sentient thought).  The model can be made more complex by the introduction of grey daisies which thrive in intermediate conditions and by introducing grazing animals and then predators (Fig. 3).

reguFigure 3: Output from Daisy World model showing how temperature is regulated.

The model does not recreate reality or simulate a process that actually took place on Earth, but provides a conceptual illustration or demonstration of the principles of self-regulation and as such it is a supremely elegant piece of science communication.

Interestingly you can run a daisy world simulation for yourself using an agent based model (  While the original daisy world model was not an ABM the idea lends itself to individual based modelling and is a nice way of demonstrating the potential of such modelling approaches.

Composing computer programs to solve scientific problems is like writing poetry. You must choose every word with care and link it with the other words in perfect syntax. There is no place for verbosity or carelessness. To become fluent in a computer language demands almost the antithesis of modern loose thinking.

James Lovelock

Temperature regulation

So we know – or at least I hope you do – that daisies are not the answer just the illustration.  This still leaves the question of how the earth has moderated its temperature.  The simple answer is through plate tectonics.

One of the most important volcanic product is carbon dioxide; in terms of volume and impact it is far greater than anything else produced by an eruption.  The longest chains of volcanoes are those found at divergent plate boundaries, such as the mid-Atlantic ridge.  Large volumes of carbon dioxide are produced by sea floor spreading and at subduction zones.  So periods of geological time like the Mesozoic which are known to have been particularly warm are often associated with periods of active plate tectonics in this case the opening of the South and North Atlantic.

So if volcanism increases the carbon content and drives greenhouse conditions, what removes carbon dioxide?  Oceans absorb carbon dioxide but by far the most significant process is weathering.  Most rock forming minerals are silicate based and are easily attached by weak acid rain.  As rain fall it combines with carbon dioxide in the atmosphere and critically in the soil to form a weak carbonic acid (CO2 + H2O – H2CO3).  This weak acid attacks the silicates to give a carbonate which is removed in solution and is ultimately deposited in the oceans.  In the equation below X stands for any cation like sodium, potassium, or magnesium which are common rock forming elements.


So weathering removes, or scrubs, carbon dioxide from the atmosphere.  The more weathering the more carbon dioxide is removed.  No weathering is favoured by warm and damp conditions and by surface area.  Think of a flat hill top, exposed rock is weathered and a weathered regolith is produced (add organic matter and you would have a soil).  As the regolith builds up it begins to slow the weathering rate since the fresh rock is increasingly at depth.  Now contrast this with a steep slope under similar conditions.  Here the regolith as it forms is removed by gravity and fresh bedrock remains at the surface to be weathered.  More weathering will result than on the fat surface.  So uplift and mountain building, both a consequence of plate tectonics, favour weathering.  So if we have lots of plate convergence creating fold mountains and uplift we tend to draw down atmospheric carbon dioxide.

thermFigure 4: The feedback between carbon dioxide, global temperature and weathering.

We are not sure what came before plate tectonics when the earth was very molten and very young, perhaps the first 0.5 billion years or so.  But with the advent of plate tectonics came movement and with it the creation of continental crust.  This was probably formed by the accretion of volcanoes along continental edges and their erosion to create sediments.  Slowly by the processes of subduction at convergent boundaries continental rocks were formed.  We call these ancient pieces of crust cratons or shield areas.  The effect was to create land surfaces for weathering drawing down carbon dioxide rapidly.  Not only was the process creating land for future life but also terra forming the atmosphere.

The faint sun in the early days of the Earth was countered by a thick greenhouse atmosphere, helping to retain heat.  As the crust and weathering kicked in the carbon dioxide levels began to fall rapidly.  Terra forming by bacteria and algae boosted oxygen levels at the expense of carbon dioxide.  As the solar constant increased the earth needed less greenhouse gases.  The complex interaction between volcanoes, plate tectonics, weathering and the evolution of life is responsible for maintaining global temperature in a equable state.  It is perhaps odd to think that life of earth was dependent on greenhouses gases.

Final word: to live or not?

Lovelock and his colleagues were brilliant agents of ‘spin’.  The choice of Gaia and the implication that the Earth was something to be revered as a living system was inspired.  Unfortunately it also caused many more staid scientists to shake their head and shrouded the scientific value of their core ideas in a lot of mystic metaphysical nonsense.  It all depends on how you define whether something is living.

They never set out to create a teleological model or to imply that Earth processes were driven by a higher ‘purpose’ simply to demonstrate how a complex system could self-organise.  Complex systems whether living or not can result in emergent behaviours in which the sum is greater than the component parts.

What distinguishes a Complex Adaptive System (CAS) from a pure multi-agent system (MAS) is the focus on system survival and characteristics such as self-similarity, complexity, emergence and self-organization. A MAS is defined as a system composed of multiple interacting agents but in a CAS, the agents as well as the system are adaptive. Complex Adaptive Systems are therefore characterised by a high degree of adaptive capacity, giving them resilience in the face of perturbation.  The Earth is an example of a CAS, resilient in the face of perturbation, a collection of self-similar agents adapting in ways that the system behaviour emerges beyond the behaviours of the individual agents.  The behaviour of the collective is not predicted by the behaviour of the components.


Charlson, R. J., Lovelock, J. E., Andreae, M. O. and Warren, S. G. (1987). “Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate”. Nature. 326 (6114): 655–661. Bibcode:1987Natur.326..655C. doi:10.1038/326655a0.

Lovelock, J.E. (2000) [1979]. Gaia: A New Look at Life on Earth (3rd ed.). Oxford University Press. ISBN 0-19-286218-9.

Lovelock, James (2007). The Revenge of Gaia. Penguin. ISBN 0-14-102597-2.

How to find instructions and tutorials on the web

If in doubt Google it! It is a good motto to have provided you have an internet connection.  Doesn’t have to be Google but the principle holds.   I am often faced with new tasks or worse i knew once but have forgotten.  I keep a notebook of web links and pasted information under a heading of ‘how to’, but I often need to seek further guidance.   Stretching your skill-set is a way of investing in yourself.  I do it all the time, so should you!

So let’s say you have do something in Adobe Photoshop which is unfamiliar or worse you did a few months ago and have forgotten!  It could be true of any software and many other skills.  Using a ‘how to . . .’ search in Google will surface most answers.  You simply need to select the best ones and compare a few posts.  The first answer you read is not always the best.  Here is some guidance on using Google, or any other search engine to its best.

Boolean Searches

Boolean searches allow you to combine words and phrases using the words AND, OR, NOT and NEAR (otherwise known as Boolean operators) to limit, widen, or define your search.  George Boole was an English mathematician in the 19th century who developed “Boolean Logic” in order to combine certain concepts and exclude certain concepts when searching databases. Most search engines use Boolean Logic.  Using Boolean Search terms you have two choices: you can use the standard Boolean operators (AND, OR, NOT, or NEAR), or you can use their mathematical equivalents.

  • The Boolean search operator AND is equal to the “+” symbol.
  • The Boolean search operator NOT is equal to the “-” symbol.
  • The Boolean search operator OR is the default setting of any search engine; meaning, all search engines will return all the words you type in, automatically.
  • The Boolean search operator NEAR is equal to putting a search query in quotes (i.e., “blood splatter analysis”). You’re essentially telling the search engine that you want all of these words, in this specific order or this specific phrase.

In summary, therefore, using AND narrows a search by combining terms; it will retrieve documents that use both the search terms you specify.  Using OR broadens a search to include results that contain either of the words you type in.  And finally using NOT will narrow a search by excluding certain search terms.


So you what to create a plate of photographs to go in your coursework.  You have read the guidance and attended the lectures but you are still struggling?  Then ask Google.  If you don’t quite get what you are looking for the first time, re-phrase the question and also think laterally – ‘this is not quite right but I could use this technique and may be that one . . . to solve my problem’.

Once you have found something that is useful and quite informative it is a good idea to keep hold of it for future reference.  Now copying the URL to a notebook, especially an electronic one is a good idea.  Don’t just rely on bookmarks because they are browser and computer specific.  I also paraphrase some of the information to make my own crib-sheet especially if its something I am likely to use a lot.

 “There is so much information out there on the web!”

“Use it discerningly!”

“Also remember in software there is often more than one way of doing the same thing; one way is not necessarily any better than another so don’t stress.”

Making an argument

In a subject like geology or physical geography  there is no absolute answer, you can’t simply look up the solution in the back of the book.  You have to find and balance the evidence and make an argument from it.  Just as a barrister makes an argument in a court room geographers have to do the same.  They need to evaluate the evidence, marshal their ideas and present them coherently so that they win the day.  That is what a scientist does when writing an academic paper.  They  collect some data or conduct an experiment,  propose an explanation or hypothesis on the back of this and the marshal their own and others’ evidence (from the literature) to make the case.  Science can be quite gladiatorial with one scientist proposing an idea that another may oppose and attack.  This critical debate lies at the heart of our discipline and helps us winnow good ideas from bad.  In other areas debate is also essential.  For example if you are advising a decision-maker you need to articulate the evidence fairly and appropriately separating areas of fact from interpretation.  In doing so you need to make a balanced argument that is fair to all the evidence and stakeholders.  A geographer brings their unique spatial-analytical skills to bear in this way and makes an argument with words, diagrams and maps.  Whether expressed orally or in writing learning to make an argument is a critical skill and has to be learnt the hard way through practice. 

Words are how people think. When you misuse words, you diminish your ability to think clearly and truthfully.

When you use words loosely, without care and consideration, you erode trust in yourself and in what you’re saying. When you squander words, you diminish your power.

For good ideas and true innovation, you need human interaction, conflict, argument, debate.
Margaret Heffernan

Geographers make critical arguments using a range of different types of spatial data.  In the real-world this may be to influence a decision- or policy-maker, justify a position taken or a proposed course of action in the face of a problem.  Ensuring that your interpretation is valid and prevails is a vital skill for all geographers to learn.  It is important to note that there are often no absolute answers, no one perfect position or solution, simply a well-argued and convincing solution.

The Physical Geography Coursework 2018/19 is designed to make you think about geographical data and to then advance an argument using that data and concisely.

So what is an argument?

An argument is a clearly expressed, balanced, point of view supported by evidence.  Essentially it consists of a ‘claim’ that is evidenced with due consideration of possible ‘counter-claims’ or alternative interpretations and points of view.

Most geographical ideas are debated by someone, somewhere, at some time. Even when the material you read, hear or watch is presented as ‘fact’ it is in truth more likely to be one person’s interpretation of that information.  In the context of your course work it provides: (1) proof that you understand the material; and (2) demonstrates your ability to use or apply that material or understanding.  The latter point is important and can be done in several ways: you can critique the information, apply it to something else, or explain it well.  It helps however to have a particular point or position on the material; this constitutes a ‘claim’.

Clarity and structure is the key to success in writing.  The human form is supported by a skeleton (its structure), remove that skeleton and we are in the words of Spock ‘just bags of water’.  The structure you adopt depends on the aim of the piece, but the following are worth bearing in mind:

  • Your argument needs to be well-structured. You should start with a strong opening statement, an introduction if you like, in which the aim and ‘claim’ are clearly stated with some basic ‘signpost’ statements as to what is to follow.  This should be followed with the three/four key supporting reasons each with evidence or examples.  You should then introduce alternative or ‘counter-claims’ before returning in the conclusion to you ‘claim’.
  • You need to stay focused to the stated aim and to the structure. There is no scope to wander off and you should always keep the point.  No bonus points are given for digressions however erudite they may be.  If you stray you will weaken your argument and end up with a ramble or simply a dump of information.
  • In a coherent argument, all the parts relate to one another clearly flow one after the next in a logical order.
  • In terms of writing, development means stating a point of view (claim) and then supporting it with well-chosen reasons and evidence or examples. A good argument takes the reader by the hand along the path of the argument without allowing the reader to digress or get lost.

Different types of argument will require slightly different approaches or tacks.  It is often good to shake things up and to vary the approach.  However as a guide the following can be used for a 500-1000 word argument:

  • One or two sentences that state the problem, its importance and your perspective or point.
  • Before you start to write list the points in support of your claim.  Now rank them in order of importance.  Ask yourself how you can evidence each one; note this evidence under each one.  You are now ready to write.  Take the first three or four points.  Write about each providing the supporting evidence.
  • Counter-points. Be balanced are there alternative perspectives on the data?  List the counter-points and associated evidence and rank them in order of strength.  You are now ready to write.  Take the first two or three alternatives and present them fairly, then point out in a polite and moderate way how they fail to explain the evidence.
  • Return to you claim or central point restating briefly why it is the most valid perspective in your view.  Explore any implications that follow from your conclusion.

A good argument should contain references that are pertinent to the points being made and to evidence the contribution of other people’s work to your argument.  It should also be illustrated as appropriate.



Useful web-links include:

Details on the BU referencing guide can be found at: