By Mike Johnson
How does AGW work? By adding heat-trapping gasses to the atmosphere by burning fossil fuels. It really is as simple, as inescapable, as that. The heat trapping gasses are called Greenhouse Gases (GHGs), and the main one, carbon dioxide (C02) was first identified as far back as the late 1600s, right at the birth of modern chemistry, by a certain Jan Baptist van Helmont who detected the gas when burning charcoal.
At that stage it was just dawning on us that what we call ‘air’ is made up of a number of gasses. Over the next two hundred years or so we discovered that C02 is one of a class of gasses possessing the ability of trap heat in the atmosphere. That is, what we call infrared radiation; the heat given off by a fire, or our bodies, which cannot be seen by the human eye. These Greenhouses gasses include, methane, nitrous oxide, ozone and water vapour.
While being described as ‘trace gasses’ because they occupy less than 1% of the total atmosphere, their importance was recognised early on. Without their ability to absorb and emit heat there would be no life on earth. It would be boiling hot where the sun fell and deep-space cold in the shade. The heat spreading properties of GHGs makes warmth at night possible. Without those trace elements the temperature on planet earth would be 33 C° colder than it is now.
A good way to think of C02 is imagine an invisible porous blanket covering the planet. Sunlight passes right through it unimpeded, but it blocks the escape of radiation within the thermal infrared range – in other words, heat. It doesn’t block it completely of course, just the right amount to create the ‘Goldilocks’ climate of the past twelve thousand years, the period known as the Holocene. During the Holocene, which provided the climatic basis for the rise of human civilization, the levels of C02 remained remarkably stable, somewhere between 260 and 280 parts per million (ppm).
As far back as the 1870s and 80s it was speculated that since the Greenhouse Gasses did hold heat, unlike the major gasses, nitrogen and oxygen, altering the balance of them might cause a problem, but without any evidence it remained a speculation until the 1950s, when what we now call the Greenhouse Effect was confirmed. The idea was treated as Science Fiction, and to many it still has that feel to it. It seemed back in the 1950s and before, as it still seems, impossible than puny little mankind could influence vast climatic conditions. It beggared belief, flew in the face of common sense. That attitude was possible, even sensible, for the times when there were about three billion people only on the planet, and well before China, India, Japan and South Korea cranked up their industries. We now have seven billion people on the planet, and the rise of global industry is starkly illustrated by this chart showing industrial C02 emissions.
Looking at the chart it’s easy to see where the extra C02 is coming from to cause the planet to heat up. Earth has stored all that carbon safely underground and we, in our wisdom, dig it up and burn it and put it into the air. Again, it’s not within the laws of physics, of thermodynamics, to put this much C02 in the air without heating the planet. The heat has to go somewhere. This is causing an energy imbalance which, as C02 persists in the atmosphere for several hundred years, is not quickly rectified – all the more reason for swift action.
When I was wide-eyed teenager, I read short stories in which colonists would ‘terraform’ planets, that is, pump the atmosphere of a barren planet with earth gasses and, after some hundreds of years, voila! you have planet fit for human occupation. In effect, by radically altering the balance of its trace gasses we are inadvertently terraforming earth at the headlong pace – pretty soon, voila! and you have a planet unfit for human occupation.
As you see, C02, (and this applies to the other GHGs) are not pollutants in themselves, like coal soot, but are damaging in the wrong quantities. The silliest thing I’ve heard said of C02 is that because we breathe it in and out it can’t be bad for us. That’s like saying because we need to drink water we can’t drown in it, or because a motor needs petrol it can’t be flooded. The next silliest thing I’ve heard said is that because C02 is plant food, more of it must be a good thing. Try applying that logic to your evening cocktail and see what happens.
The best that can be said for it is it might apply in limited conditions, in limited circumstances for a limited time. Overall the effect is proving to be devastating.
It is sometimes said that if we could see radiation we would not be so tolerant of it. Think of what would happen if we could see the radiation spewing from Fukishima, and see the ocean along that coast glowing with the stuff. The same applies to the odourless, tasteless, invisible C02 and its cousins. The following graphic is a dramatic way to illustrate just how much C02 we are, collectively, producing. Imagine if you had to haul it to the street everyday.