The global warming debate - a personal perspective

Making decisions under uncertainty

In both our personal and collective lives we are forced to make decisions under uncertainty. What's worse, even after the fact we cannot be sure we made the right choice.

The Reserve Bank raises interest rates to avert an increase in inflation. In so doing it inflicts hardship on people with mortgages and business loans. The concomitant rise in the Aussie dollar makes life harder for exporters. However inflation remains under control.

But would inflation have remained low anyway? Was the pain the Reserve Bank inflicted necessary? There is no way of being certain.

Your doctor advises you to take a class of medications known as a "statin" to control your cholesterol levels. He tells you that will reduce the risk of suffering a heart attack. Fearing some of the well-known adverse effects of statins you do not take his advice. Two years later you suffer a heart attack.

Could you have avoided a heart attack if you had taken the medication? Again, there is no way of knowing. Many people who suffer heart attacks are taking statins? The most that can be said is that taking statins has been shown to reduce the probability of heart attack in certain circumstances. They are risk reducers, not preventers.

Decisions about climate are no different to the ones I've just described. We all have to make decisions under uncertainty and even after the fact we may not know whether we've made the right call. That is the real world. That is the human condition. Let's not kid ourselves that it can be any different.

Is there a decisions to be made?

The forgoing begs a question. Is there any decision that needs to be made about climate? Are there any actually risks in continuing to pump CO2 into the atmosphere?

Here, in outline, are the facts.

• A group of wild-eyed scientists did not dream up the theory of anthropogenic global warming (AGW) out of nothing. Well-established laws of basic physics suggest a significant impact on climate if we continue pumping CO2 and other greenhouse gases into the atmosphere. The theory of AGW has a firm basis in the laws of physics.

• Yes there are many uncertainties and anomalies but, taken as a whole, the evidence tends to support the physics. The case for anthropogenic global warms (AGW) has not been made beyond all reasonable doubt; but the preponderance of evidence points in the direction of human induced global warming. That is the best we can ever hope to do. To expect more is unrealistic.

• The average lifetime of a CO2 molecule in the atmosphere is 60 - 100 years. A planet-wide climate system responds slowly to changes in atmospheric content. Thus if we do find that pumping CO2 into the atmosphere produces adverse consequences we shall be stuck with them for a long time even if we stop emitting.

• The definite albeit difficult to quantify risks coupled with the difficulty of reversing the effects of extra CO2 in the short term suggests that the only prudent response is to begin to take steps to reduce CO2 emissions. We may not know everything but we know enough to say that the risks of continuing with business as usual are high.