Models use mathematical equations for prediction. If those equations are speculative, wrong, highly inaccurate, and unverified, then the model is no better. Unfortunately, this CSIRO model has all of these problems.

I am a physicist. Physics is the most exact of the sciences. Branches of physics such as Newton’s laws of gravitation, and electromagnetics are based upon equations with an uncertainty of a tiny fraction of a percent. They can usefully predict the unknown, such as calculating where Pluto will be in a few years’ time – so a spacecraft can do a fly-by.

One of the most important things taught to all physicists is that an estimate of uncertainty MUST accompany any measurement or prediction. If the uncertainty in the prediction of the position of Pluto was too large, then a scientist would not know what course to use when sending the spacecraft. The prediction is useless, and known to be useless. If that is the case, one must be open about it.

The CSIRO model has dozens of equations, which represent the influence of agriculture, crown of thorns starfish (COTS), and climate change.

https://www.theguardian.com/environment/2021/apr/29/life-support-measures-could-buy-great-barrier-reef-another-two-decades-study-finds Many are unreasonable or worse. For example, how can one write an equation for the negative effect of COTS when there is big debate about whether the plagues are totally natural. The uncertainty margin is huge. And there are good reasons to expect that modest climate change will make the reef grow better – after all, the best coral is to the north of Australia where the climate is hotter.

There is no useful measure of uncertainty so the CSIRO model predictions have little value. It is based on equations which are often at best highly speculative and in some cases plain wrong. That is why I have given the uncertainty margin as +/- x% in the picture.

But this new doom-model gets worse as it also purports to model interventions to save the Reef such as making clouds to shade the coral. This cloud shading is seriously proposed and considerable sums of money are being spent investigating the possibility. But simple calculations can show this is totally impossible, especially for the Reef which is 2000 km long. The new model also looks at the effects of engineering works to stop the Reef breaking apart due to climate change – another serious, but completely impossible, suggestion.

I have to agree with some sceptical comments made by Prof Hughes of JCU about these engineering interventions. He was the one who made complaints about my comments that there are systemic QA deficiencies in many of the Reef Science institutions, and those complaints led to me being fired. But he is absolutely right in this case.

https://www.theguardian.com/environment/2021/apr/29/life-support-measures-could-buy-great-barrier-reef-another-two-decades-study-finds

To be fair, models such as the new CSIRO model can have a useful purpose even if they cannot make a useful prediction. They can be used to determine where more work needs to be done so that a useful model can be developed for the future. For example, we need better information about the life cycle of COTS.

I have been pushing for a quality audit on Reef science. The results of this doom-model were reported around the world. It needs to be thoroughly audited.