I approach this climate debate from two other different perspectives: medical, where confidence levels are calculated quite accurately, and risk management.

My question is, can someone identify the flaw in the following simplistic analysis:

Anthropogenic global warming requires three assumptions or ifs to be valid:
1. there is continued global warming, not just a recent upward part of a cycle;
2. This is due to increasing CO2 levels;
3. This in turn is due to human activities.

My risk management expertise suggests that for AGW to be valid requires a multiplication of the three risks to result in a high value, eg IPCC puts the first at 100 percent and the second two combined at greater than 90 percent, giving a ‘very likely’ conclusion.

However my medical expertise suggests that while calculating confidence levels for a series of points on a time graph is relatively easy, similar calculations for correlation factors is not, particularly when there are many inter-related effects and sometimes positive or negative feedback links between these factors.

How then can anyone give a greater than 90 percent confidence level for the second and third ‘if’s combined?

My simplistic guess is that with the recent stabilisation of the global temperature the first is likely to be a lot less than 100 percent. The second and third assumptions are widely disputed by many geologists and some climate scientists so would have confidence levels well below 80 percent.

The combined risk is therefore likely to be less than 50 percent. In which case what then?

I would appreciate an explanation of the flaw in my reasoning. Lord Monckton simply said my mathematics is unsound but did not say why.

If you’re going to do good science, release the computer code too
Programs do more and more scientific work – but you need to be able to check them as well as the original data, as the recent row over climate change documentation shows.

Note also the assumption that you can get the data the authors are using..

When I was doing O Level biology, it had to be appended to the paper.

Times seem to have changed.