The central question no politician is asking (and very few journalists who are paid to ask questions): How much warming will the carbon tax prevent?

The rationale of the deceptively misnamed carbon tax is that we need to reduce CO2 emissions in order to stop the planet warming. The Government has pledged to reduce our CO2 emissions by a whopping 5% by 2020.

When Andrew Bolt asked Climate Commissioner Tim Flannery the question last week Flannery was unable (or unwilling) to answer the question. That's surprising really because for a scientist with an interest in the question, the calculations are very simple. The EU's climate Change commissioner also had a similar problem when asked the question a few weeks ago.

But Lord Monkton, also a mathematician, has no such difficulty. Here are his conclusions, based on the IPCC report:

If Australia goes it alone with the cuts in CO2 emissions: 0.00005 Celsius

And if the whole world reduces its emissions by 5%: 0.004 Celsius

As Monkton points out, the latest estimates by climate scientists in the warming camp is that the IPCC figures have over-estimated the effects of CO2 by a factor of 2 to 3 times.

So tell me again, why are we doing this?