Estimates

The table summarises other estimates of UK average emissions (tonnes per person per year). Some sources give merely the CO2. Others include methane and nitrous oxide greenhouse gas emissions converted into an 'equivalent' quantity of CO2 ('equivalence' being according to standard formulae), and so give a total as tonnes CO2 equivalent per person per year.

CO2	Total greenhouse gases as CO2 equivalent	Source	Notes
10		[MH, 3]
10.7		[Carbon Trust, 7]	From UK consumption - i.e. including imports
10.8		[WWF, 17]	From UK production
11		[5]
11.9		[WWF, 17]	From UK consumption - i.e. including imports - i.e. 1.1 more than UK production above
	12.5	[CG, 10]
	13	[LM, 1]

There is reasonable agreement with our estimate of 9.84 tonnes CO2 per person per year, and with our estimate of total greenhouse gases of 13.4 tonnes equivalent per person per year (given on our Basic information page.

Uncertainties

The range of figures reflects the difficulties in calculating an accurate up-to-date average figure, as follows.

One problem is that detailed figures tend to be not up to date. The most detailed figures available for the UK seem to be those in source [7]. This is a document published in 2006, quoting figures published by the University of Surrey in 2005, based on UK Government statistics of 2002 and 2004. The total has clearly changed since then.

Greenhouse gases other than CO2

It is not clear how to allow for greenhouse gases other than CO2. The two most important are methane and nitrous oxide. Methane persists in the atmosphere for around a decade [6], and nitrous oxide for about a century [6], whereas there is much uncertainty about the fate of CO2 emissions. So while we know that methane is generated by deforestation, and the production of rice and cattle, it is not clear how we should convert methane generated by someone's meat-eating lifestyle into an equivalent amount of CO2, because it depends on which timescale we are considering.

But for the purposes of informing people about the ways in which their lifestyle is damaging the world, and providing a single summary figure in the form of calculator, it is necessary to pick on one timescale - and 100 years is the standard figure chosen.

References

See Reference List