Global warming and externalities

How a carbon tax can "solve" global warming

Tim Worstall (yes, when he's not trolling he's quite good) has a piece up at the Telegraph explaining how carbon taxes work, and why they could "solve" global warming:

In economic theory, the problem here is that my actions that create emissions also damage someone else. But I don't have to pay for the damage I've caused. This is called an externality and the economists' solution is something called a Pigou Tax. That is, we add a tax equal to the damage I'm doing, so that I do pay for that damage.

Worstall cites the Stern Review's figure of $80 per tonne of CO2 as a good starting ground for where to set a carbon tax, and explains why it's the most efficient way to deal with climate change:

As a made-up example: my car emits one tonne CO2 when I drive it to buy fresh bread for lunch. That's $80 of damage I cause in the future by doing so. But the benefit to me is trivial: if you paid me 50p (alright, £5 in the rain) I'd cycle instead and not emit the CO2. The value to me of driving is that 50p; the costs to someone else are the $80. Clearly, this is a bad deal for everyone else: they're bearing costs much greater than the benefit to anyone at all. An $80 a tonne tax would get me cycling and that would be a good thing: I've stopped doing something where the benefit is lower than the cost.

However, we've a pregnant woman in pre-eclampsia. She needs to go to hospital in an ambulance which is going to emit that tonne, that $80 worth of CO2. Without it she and the child will be dead; with it they'll be fine. We usually value a statistical life in the £2 – 3 million range. That's what the railways will spend on safety to save a life on average. Or we could use the £50,000 that NICE applies to one year of good-quality life. If your drug treatment costs more than this, then you won't get it on the NHS; less and you might. Different numbers but much the same outcome: burn that fuel and damn the $80 of future damages, because they're much lower than the benefits that are achieved right now from burning that fuel.

This efficiency is why a carbon tax – or the harder to impose, but fairer and economically identical "cap-and-trade" system – really is the best way to deal with global warming. By definition, it deals with "bad" emissions while allowing "good" ones, and it does so far better than a legislature could ever hope to with a sprawling network of tariffs and subsidies.

But Worstall does somewhat overstate the case in one area, when he writes:

The other part [of a reader's question] – what's the point if we're not going to spend the money on green projects? – misunderstands the purpose of the tax. We're not trying to raise money: we're trying to change prices.

Changing prices is only half the effect of a carbon tax – or any Pigou tax. The other half is compensating the "victim" for their loss.

Suppose we live in a little two person economy where every tonne of CO2 you produce causes $80 worth of flooding damage to me. Imposing a carbon tax solves half the problem, in that it stops you polluting if you only get $10 benefit from it. But it doesn't solve what happens if you can make $100 from polluting.

In that case, you pay $80, and make $20 profit. I'm still left with $80 of flooding damage. The proper use of the money raised is to compensate the me for that loss. Otherwise, a tax which merely sorts out externalities becomes a revenue-raising tool of Government. In practice, this means that money raised from a carbon tax should be used on "green projects".

Which would annoy Worstall's fellow Telegraph blogger James Delingpole.

Anti-carbon tax protestors in Australia. Photograph: Getty Images

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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Who benefits, and who loses out, from David Cameron’s housing plan?

The prime minister’s plan to scrap the affordable rental homes requirement, explained.

What has Cameron actually announced about housing today?

In David Cameron’s closing speech to the Conservative Party conference in Manchester today, he announced plans to change the requirements to build affordable rented homes in new developments so developers can build "starter homes" instead of homes to be leased at affordable or social rents. 

The policy is geared toward ensuring that his party meets its campaign pledge of building 200,000 new homes by the close of this parliament, by taking the emphasis off renting (affordable housing requirements usually refer to rented, not owned houses) and onto owning. It should, claims Cameron, take us from “Generation Rent” to “Generation Buy".

What sort of houses will they build instead?

"Starter homes" are homes sold at 80 per cent of market rates to those under 40. These an be sold for a maximum of £450,000 in London, and £250,000 everywhere else. 

That sounds quite good!  

There is a chance that Cameron is right – that removing these obstacles will make developers move through the planning process more quickly, and will help boost the number or houses built. 

But (and this is a big but): most predictions so far are that this won’t happen, and if it does, it’ll only help a very specific demographic. As my colleague Stephen Bush has already pointed out, the announcement is good politics, but bad policy. It makes it look like Cameron is doing something about the housing crisis, while scoring points with big property developers along the way.

My colleague Jonn Elledge, meanwhile, notes that this system could actually slow down housebuilding, as the houses will take longer to sell than they would to let. Moreover, if housebuilding is more profitable in the long run, this will push up land – and therefore house – prices. 

Who'll benefit?

Tory voters and their children, in a nutshell. The starter homes will mostly be one or two bedrooms, and will be aimed at working couples.

Shelter calculated earlier this year that a couple would need a combined income of £76,957 in London and £50,266 in the rest of the UK to afford one of these homes, which makes it clear that they're aimed at well-off professionals. If you're in a stable relationship, earn £40,000 or £26,000 a year each and are looking to get on the housing ladder, you're in luck. 

Who won't it help? 

Everyone else. Under this policy, the Conservatives are effectively redefining “affordable”, just as they co-opted the phrase “living wage” earlier this year. By most peoples' definitions, a housing option only available to those with access to £80,000 in earnings a year is not affordable. The situation outside London is a little better. 

That’s not to say the affordable housing requirements were perfect before – these, too, were defined by some councils as 80 per cent of market rents, which in many places equates to anything but affordable. Yet removing the requirement for affordable rentals leaves nothing for those unable to afford to buy, leaving the squeezed lower-middle (and most young people) increasingly in the lurch.

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.