Everyone but everyone out there in Copenhagen today agrees that a precondition of reducing emissions of greenhouse gases is to ‘get a realistic price on every tonne of CO2 just as soon as possible’.

Nick Stern’s report on the Economics of Climate Change rammed home this point so effectively that some misguided economists would now have us believe that’s all we need to do. Not so.

But it’s true that nothing much will happen without it.

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Many people (including most EU Heads of State) still think the fastest route to getting a realistic price for CO2 is to create a global trading scheme – like the EU’s Emissions Trading Scheme, scaled-up, or the proposed ‘Cap-and-Trade’ scheme in the US.

But more and more people are now losing confidence in the trading route. Those with long memories recall that it was only included in the Kyoto Protocol in 1997 as a way of keeping the Americans on board, with most EU countries actually feeling very queasy about it at the time. Ironically, when the Americans subsequently pulled out of the Kyoto Protocol, the EU was left holding the trading baby! Twelve years on, it still looks like a pretty sick little baby.

Many economists have long been of the opinion that it would make a lot more sense to tax carbon, levying a charge on the carbon content of all energy sources upstream at the point where they enter the supply chain. And more and more business leaders are coming to that same conclusion – on the grounds that they would then know what the cost of carbon would be over time, ratcheting up from a low base line to ‘a realistic’ level (i.e. behaviour-changing and innovation-driving!). This would be brought forward as soon as economies could cope.

Such tax would simultaneously generate a shed load of revenue, some of which could then be used to provide the funding required for developing countries.

In that regard, we know one thing for sure: in the current economic crisis, rich world countries are not going to be able to find big enough sums to provide the poor world with what they now need. As the EU Summit on Funding so clearly demonstrated last week – the funds just aren’t there.

So we need some new sources of funding. The current favourite in Copenhagen, being advanced by Ethiopia (on behalf of African nations) and warmly supported by Gordon Brown and Nicolas Sarkozy, is a mixture of taxes on aviation, shipping and financial transactions (the so-called Tobin Tax) – “get the bloody banks to pay for dealing with climate change”, as the populists put it!

Forgive the pun, but this one could just fly! If Gordon’s on board (as a man who refused to countenance any discussion about the Tobin Tax over the last 12 years) then anything could happen. And the truth of it is that there isn’t any alternative anyway, so we might as well bite the bullet and get on with it.