It is now becoming fairly well understood that production based national emissions metrics and targets, such as the UK's, fail to take account of emissions from net imports of goods and services. Some of us are getting to grips with the idea that national production based targets fail to track our movement towards a low carbon economy and provide a perverse incentive to import more of our goods. Encouragingly, the Commons Select Committee on Climate Change is having a review of the case for consumption based accounting.

Many of us now understand that when we import goods we currently shift the embodied carbon off the UK's books. We also know that there is a good chance that we are multiplying it by having the production done using less energy efficient industry, powered by more carbon intensive energy. The average dollar spent on primary energy in China results in three times the carbon compared to in the UK. That is partly because the energy mix causes more carbon per kilowatt hour but mainly because Chinese coal is such a cheap energy source. At Small World, we've been digging into this to estimate the embodied carbon from the burning of fossil fuel per unit of monetary output from different industries in different countries. We've been using OECD input-output tables to trace the direct and indirect expenditure on mined energy products and combining that with statistics on energy prices and fuel mixes to arrive at our estimates. The results are startling, even though some context is essential.

Two Headline results: Per dollar of output from the textiles industries in China we estimate that there is more than ten times the embodied carbon from fossil fuels comparred to the figure for the UK textiles industry. For the Iron and Steel industry the ratio is just under ten.

Essentail Context:

1) The product mixes are not the same in the two countries. If we shifted all our textile imports to UK production, the carbon intensity of our textile industry would increase somewhat.

2) Like for like prices are not the same - which is why we buy so much clothing from China. (Two contributing factors are theartificial devaluation of Chinese currency and that in Chinese textiles industry there is only one third of the expenditure on employee remuneration per £ of output that there is in the UK industry)

3) These are draft results, and although we have kicked them about quite a bit and sense checked them they are not formerly peer reviewed.

What this means Consumption based metrics that take proper account of the different carbon intesities of production around the world are a must-have for the UK. These are likely to confirm that we are a very long way indeed from decoupling economic growth from carbon. There looks to be a powerful environmental case for having more of our production carried out more locally.

I've been lucky enough to have been working with those masters of communication at the Eden Project, helping them put together carbon footpint exhibition and an online calulator using the numbers from 'Bananas' .

www.edenproject.com/carbon-calculator

Both the online calculator and the exhibition are about giving us that 'instinct for carbon' that I'm always banging on about.

The unique thing about the calculator is that it lets you compare things and drill down to see how and why things get get to have the various components of thier footprint. As you'd expect from Eden they've done a great job of making complex things clear and simple.

The exhibition itself is a Smart car full of stuff that you are invited to rummage through, all of which has a has a carbon footprint label attached.

Following my short article in Eureka magazine I want to add some further thoughts that I’m afraid arn’t good news for the electric car, and also to post up the numbers behind the piece.

First of all here’s the unabridged version of what I wrote for Eureka.

Electric Car Carbon: How low can we go?

It would be lovely to think that electric cars could be almost carbon free but there’s a catch. The electricity has to come from somewhere. The UK grid is powered from a mix of sources; coal, gas and nuclear, with a few renewables thrown in. However, when you switch power from petrol to electricity, all that additional demand has to be met through fossil fuels. 100% of it! The hydro and wind turbines can’t turn any faster to meet your extra requirement since they are already doing their best to help power the grid.  So the carbon intensity of the electricity needed for cars would be significantly higher than the current grid average. This will be the case until such time as the UK is awash with renewable and / or nuclear energy having entirely phased out fossil fuel generation. Sadly that day seems a long way off. Some have argued that charging up at times of low grid demand could help, but this would only solve the if  problem if we had moments when renewable energy was being generated that could be used in no other way.

 Whilst all this might be a painful realisation for those of us hoping for a magic wand solution, it doesn’t consign electric cars to the scrap heap. The good news is that they still stand to give us a significant efficiency improvement. The best petrol engines turn only about a third of the available fossil fuel energy into mechanical power. Electric engines can do much better than that, more than compensating from losses in electricity generation. Electric engines are also lighter, which helps to make urban driving more efficient and cuts the embodied carbon required for manufacture (provided of course, we can find better ways to make batteries).

Final Verdict: Along with cleaner, quieter streets, the electric cars of the foreseeable future should give us a carbon efficiency improvement that is well worth having, but we should bank on no more than that.

And now here are the numbers, taking account of the supply chains of fossil fuel production but not the embodied carbon in cars thmselves.

So, overall the electric car can deliver a 38% efficiency saving if the extra electricity demand is met through gas but is actually more carbon hungry than the best a petrol car can do if the electricity comes from a very efficient coal power station.

BUT there is more – and it is not good news for the electric car. Imagine a world in which we have created the batteries for the electric cars and charged them up at the quietest times of the night when the carbon intensity of the marginal demand for electricity is lowest. We then have a choice about what to do with that stored power. The most sensible alternative would be to use it to support the grid at moments of peak demand, thus saving on the the highly carbon intensive marginal demand for electricity peak moments. But we foregoe that opportunity if we spend our battery power on car travel. So it is more realistic to think of electricity for cars coming from the most carbon intensive electricity that is ever supplied to the grid. In this analysis, the electric car looses out badly to petrol, even if you were to anly credit the petrol engine with potential for 25% efficiency.

Developing battery technology is a good thing but we should use them for balancing electricity supply and demand rather than on cars.

I’m just getting my head around this incredible piece if kit. Well managed, it does seem to open up lower carbon opportunities, although I can see that it could also take me into a world of permanent busyness that probably has unsustainable consequences.

Here are some of the obvious positives:

1) Built in sat nav means there is no excuse for ever driving in the wrong direction

2) Non-car travel becomes easier more fun and more productive. Often alternatives to the car fall down just because they take to long to research. Now it is so quick to know your best train options in real time. I know there are people looking, for example, at how to encourage more people onto the busses in Cumbria. If there isn't an app to let you know when your next bus is coming, there must be an opportunity for it. And the same piece of kit means I can catch up on the news on my way to work without needing a car radio or a paper (I'll be listening to radio 4 as I cycle along the canal).

3) I haven't put it to much use yet but a free app lets me know the carbon intensity of electricity at any given moment (even though I suspect marginal demand is met through coal and gas 24 hours per day, so it may not be as simple as waiting until the average intensity of the grid is at its lowest before putting the washing on).

4) Spending money on apps is probably relatively environmentally friendly way of getting rid of disposable income.

Of course the machine itself has a significant embodied footprint ( a few hundred kg CO2e at a guess), but I should be able to get that to pay itself back before too long provided I don't loose it too quickly. The electricity it uses is negligible.

The real danger seems to be that if I'm not careful, my life will never again contain any odd moments for quiet reflection - and that might just be a critical ingredient of sustainable living.

So my overall verdict on the iphone so far? An incredible piece of technology but whether it is any good for me (or us) is all down to how it is used.

I've just spent 2 days visiting Eden - the first time I've been. I REALLY like their approach. And they are clearly masters at comunicating and engaging people. Luckily, they like my stuff too so it looks as if some good things can come out of it. I'm very pleased.

Now waiting for a snow-delayed train home to Kendal via London. I've had to transfer to a sleeper. It is all very civilised. In my spare time had a bike ride (on the folder), a walk along the cliffs, a haircut and a nice meal and got loads of work done.Thank goodness I'm not stranded in the living hell of an airport refugee camp or sitting it out in an overnight traffic jam. I'll even be at work for 9 tomorrow. The train is winning yet again.