The scientific method has created a culture that is sceptical, critical, evidence based and argumentative.

Geologists tend to put the argument that climate change is natural, happening all the time and, that, in comparison to changes in sunspot activity or the eccentricity of our orbit around the sun or continental drift, human activity is unlikely to have a global scale impact on the climate. But what was it that caused former US Vice-President Al Gore to return to schlepping all over the USA giving a power point presentation to all and sundry on increasing levels of carbon dioxide in the atmosphere?

Let me, an undergraduate, try to explain the science simply, so that people are able to engage in a real debate on what is the best way to respond to the problem of human induced increases in atmospheric greenhouse gases instead of whether climate change is real. I will call on my knowledge of three disciplines, geology, chemistry and biology.

Like all good stories it begins once upon a time.

A long, long time ago, about 4,500 million years ago, the earth formed and at first it did not have an atmosphere. Slowly, slowly, taking about 1,000 million years the parts of the earth came together and radioactivity began to heat the inner parts. Gases were ejected from the mantle and an atmosphere was created. There was very little free oxygen, what existed was in the upper atmosphere created by the dissociation of water by solar radiation.

There was nitrogen, water vapour and carbon dioxide. Early life began and after a while the early heat loving methane producing organisms were joined by those that used light and carbon dioxide to meet their energy needs and excreted oxygen as a waste product.

From carbon dioxide composing thirty percent of the atmosphere, slowly over the billennia green life on earth changed our atmosphere to one that today is 0.04 per cent carbon dioxide and nearly twenty percent oxygen. How did this happen?

In basic chemistry we are taught that within a closed system all chemical reactions reach an equilibrium.

It is reasonable to expect that the photosynthesis reaction:

carbon dioxide + water + energy from the sun = life energy + carbon complex with embedded energy + oxygen

would be balanced by the reverse process respiration whose equation is

carbon complex with embedded energy + oxygen = heat + carbon dioxide + water .

The shorthand way of writing this equilibrium is

6CO₂ + 6H₂O    ⇄     9O₂ + 6HCH

                         where    ⇄    means energy in and out.

Imperceptible geological processes buried the carbon rich organisms that died and fossilized their bodies into coal. Similarly the remains of shellfish which had removed calcium carbonate from the system in making their shells were buried and turned into limestones. The carbon rich products of photosynthesis were removed from the system, driving the equilbrium to the right and hence oxygen accumulated in the atmosphere.

So far I have called on basic geology and chemistry. Now cast your mind back to first year high school science and some very basic biology. Did that equation above seem familiar to you? Do you have faint memories of the carbon cycle, where green plants take energy from the sun and in the presence of carbon dioxide and water create carbohydrates and exhale oxygen – photosynthesis and plants and animals utilise oxygen to burn the carbohydrates getting energy and exhaling carbon dioxide – respiration?

I'm going to call this the active carbon cycle.

For millions of years the return of fossilised carbon to the active part of the carbon cycle has been by slow geological processes. Subducting continental plates carry carbon rich sediments and rocks down into the mantle and finally carbon dioxide is returned to the atmosphere by volcanoes. It is a slow process. Whether the fossil carbon remained part of the active carbon cycle or re-entered a fossilisation process depended  if it was it quickly buried in sediment or submerged in a bog and prevented from decaying, once the plant died.

I'm going to call this the fossil carbon cycle.

Now consider a global scale equation, the balance between the active carbon cycle and the fossil carbon cycle.

Carbon dioxide    ⇄       carbon + oxygen

CO₂     ⇄     O₂ + C

 

 

 

At this point I have moved to another page :A distracting side argument

The question now is whether the scale of human acitivity is enough to make a difference to the equilbrium?

Continental drift is measured in centimetres per annum. How quickly in comparison do we dig up the coal and pump oil out of the well?

Once upon a not so long ago time, as well as a continuous global belt of tropical rain forests, the temperate zones of Europe and north America were also covered with forests. Which plants will remove the carbon dioxide from the atmosphere?

The chances of trees being buried in a bog are low because many wetlands have been drained for agriculture and mangroves removed for development and shrimp farming.

Clearly understanding these processes we can now ask ourselves the difficult questions.

Is human induced global warming a possibility?

How will we lock up, sequester, the (fossilised) carbon dioxide which is the waste product of our modern life?

Given the worst case scenario of significant rises of sea level, what will we do about the people in the western suburbs of Adelaide whose houses will be under water? And what about those millions of coastal dwellers in Bangladesh, the Nile delta and the low lying Pacific Islands?

What am I prepared to gamble that global warming will not result in desertification but in increased rainfall? Will I live long enough to see the consequences of my behaviour.

It is one thing to burn coal and oil ignorant of how they were formed as happened at the beginning of the industrial revolution. Is it right to allow corporations to act unchecked and devastate the planet for profit?

What if I'm completely wrong and climate change does not occur? See Costs and Benefits.