Why I believe Anthropogenic Climate Change is Real

I have heard so much disinformation about climate change lately that I feel I can't be silent any more. Yesterday's release of cabinet papers that disclosed the clarity that our political leaders were given 30 years ago, while some still claim the science is not settled, was the final straw. As someone trained as a scientist, and as a communicator, I feel it is important to offer my perspective. You may have other pet scientists you may wish to listen to, but I will attempt to build my argument on established facts and will try to point out where some of the points for (often mischievous) misunderstanding may occur,

Atmospheres and Heat Transfer
The Earth is a planet whose primary source of heat is the sun, This heat is transferred by infrared radiation. The atmosphere plays an important role in this process. The moon surface, having a minimal atmosphere absorbs some of the infrared radiation, and reflects the rest of it back into space. For this reason, the part of the moon that sees the sun at any point in time sees extreme heat and the part that faces away from the sun sees extreme cold. In contrast, the atmosphere of the earth adds a number of different factors to the mix. Things such as clouds (or volcanic or bushfire smoke) can cause more of the sunlight to be reflected (technically, the planet's albedo increases) and have a cooling effect, the very mass of the material gives a buffering capacity, and the atmosphere itself has gases that convert solar radiation into heat. These are what are commonly called greenhouse gases.

Infrared absorption by greenhouse gases
The earth would be uninhabitable if it were not for the presence of greenhouse gases. These are a set of components of our atmosphere which have the property of strongly absorbing infrared radiation. I, by training, am (among other things) and infrared spectroscopist. I used the ways in which particular gases absorb infrared radiation to study the ways in which those gases interact with the surface of coal to assist in my little bit of the CSG development process. There are a number of naturally and synthetically occurring gases in our atmosphere which perform this function. The primary gases in this suite, in order of decreasing concentration are water vapour, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons and hydrofluorocarbons.

Changes in greenhouse gas concentrations and the "Carbon Dioxide Hypothesis"
For decades scientists have expressed a concern that the concentration of these gases is increasing with human activity over time, and have pointed to the fact that this would be expected to increase the total (global) heat of the planet. Unfortunately, some seized on an misunderstanding that this means that this would be a homogeneous effect with all temperatures being observed to rise in all places (I must admit that this is a much more satisfactory definition of "global"), but the earth has a number of strong dynamics that effect our weather events on a local scale, and there is a difference between global averaging measurements and the effects in each individual local climate.

In terms of human effect, some people ask why we only speak about a small part of the equation. Water is by far the largest contributor to the greenhouse effect, and we do not speak about it much at all. The thought is that, as this is out of our control, relatively small variations in the levels of water in the atmosphere due to natural effects have the potential to swamp the relatively small components that humanity adds through its activities.

The difference is that water has a clear mechanism by which its atmospheric concentrations are maintained at a generally stable level- the water cycle, and don't we need some of that rain about our place at the moment!

I will talk about carbon dioxide later, but wish to note that methane and some of the other greenhouse gases listed above are quite opposite to water, once these gases are released into the atmosphere there are only quite slow mechanisms for them to be removed.

Carbon dioxide is a middle-case scenario. There are a number of mechanisms by which excess carbon dioxide can be absorbed by the planer, particularly absorption by the oceans and the life-giving process of photosynthesis which occurs in plants but more predominantly in sea life. This capacity is known technically as buffering but is also known as carbon sinks or carbon banks. This makes it difficult to estimate the exact effect a particular amount of carbon dioxide released will make to the global concentration and thus the climate (and it is this factor, rather than whether there is an effect that is under discussion in mainstream scientific discourse)

While the concentration of carbon dioxide is known to be rising, this is also something that has varied over the life of the planet. However, there has been a rapid rise from a prior historical record estimated at 300 ppm to our current averages exceeding 400 ppm.

Carbon sinks v carbon banks
One of the areas in which there is some discussion is the concept of a carbon sink. The earth has shown mechanisms by which carbon dioxide has been removed from the atmosphere in the past and taken out of circulation. Two prime examples would be the deposition of limestone (carbonates) and fossil fuels, as well as the obvious examples of storage in timber.

The problem with seeing these systems as sinks is that we can assume that they will always function in the way they have historically. Our use of fossil fuels has turned that part of the equation into a bank from which we are making withdrawals on a historical scale, and the burning off of forests to either aid development or through fires also pose significant withdrawals.

The catastrophic fringe of the climate movement are warning that we cannot take the historical mechanisms and sinks for granted as they are also subject to affect by climate. I must say, that while I do not share in their despair, they do have a good point. The deposition of limestone comes from the absorption of carbon dioxide by marine life into their casings and them settling to the sea floor. While we may think that this mechanism may accelerate with increasing carbon dioxide concentration, there is another affect in play. The increased concentration of carbon dioxide in the seawater is having a small but significant impact on the oceans by making the water more acidic. The change in acidity of the water means that it is harder for these organisms to form their calcium casing that lie at the heart of this process.

All this adds up to the fact that, even though the planet has been able to handle the changes in carbon dioxide levels that have occurred to the point, there are enough reasons for concern that I believe the wisest course of action is for us to seek to reduce our carbon dioxide emissions in a planned and managed fashion (and I wish we had started this 30 years ago).

But what about the other variables?
 One of the common arguments I hear is that the earth has a variable climate, and climate change is a given. This is indeed true. However, the rapid changes have tended to be towards the cooler end of the scale (often associated with catastrophic events such as meteor strikes or volcanic eruptions) but there are examples of ecosystems which have been able to adapt to these changes over time.

One example of this is "cloud forests" where plant life on tropical mountains exists at the point where the water in the air condenses into mist. As temperatures increase and decrease, these systems would have needed to move up and down the mountain face to survive. They are currently struggling because the rate of change is higher than what they can cope with. I have a friend whose whole doctorate is in predicting the number of species of native plants in my country will be made extinct because of our current rate of change and the restriction of habitats for the ecosystems to move into.

In recent years my own country, we have had a fire in a temperate forest which is not capable of tolerating fire where the trees have been estimated as being 1000 years old, we have also seen rainforests of significant age (which also do not tolerate fire) burn in recent years. It is not business as usual.

So, how do we face this threat, who should pay?
I think this is the question that lies behind much of our opposition to action. If we choose to make changes, people are going to suffer. The sad thing to me, is that this has become a polarisation point between those who see nature as its own good, and those who see it solely as a source of materials for human flourishing. Civilisations through history have learnt that if you exceed the capacity of your natural systems, disaster occurs. Our particular civilisation has seen the growth of many mechanisms by which we can control many of these potentially disastrous factors. Perhaps we will be able to continually develop technologies to stay ahead of the catastrophe curve, but I would not exclude the re-establishment of the concept of land care as one of the developments we may need. It will mean a change for both sides of this discussion, but it is one we need to have.