Nothing would incentivise tree planting quite like a proper price for carbon.

In 1991, Sweden put a levy on greenhouse gas emissions, one of the world’s first carbon taxes.

Initially, the tax was focused on motor fuels and on domestic and office heating. Fuel producers paid about €24 for each tonne of CO2 that their products emitted to the atmosphere when burnt. That cost has risen steadily since and is now about €114 a tonne. If that sounds like a big bill, it is: the price of gas supplied to British homes today would go up by more than 50 per cent if the Swedish tax rate was applied…