The other day I was reading a church report which stated that the carbon footprint for the average person in the UK is 4.85 tonnes of CO2 per person per year. This puzzled me because I’ve recently calculated my personal carbon footprint with carbonIndependent which states the UK average is 14.1 tonnes and with the WWF who use a target of 10.56 tonnes (for 2021). How can these be so different, and which one is correct?
The report cites the figure as coming from Our World in Data which confirms the 4.85 tonnes figure (for 2020) and ascribes this to an article Global Carbon Budget 2021 in the journal Earth System Science Data. The quoted figure has been calculated by dividing the total amount of CO2 emitted within the UK by its population.
There are several problems with this approach. The first is that it is the production-based figure which ignores any CO2 that has been used to make products in the rest of the world that have then been imported into the UK. A much more important statistic is the consumption-based footprint which was 7.7 tonnes (according to a different analysis provided by Our World in Data, for 2019, the most recent year for which there is data).
Another issue is that we emit other greenhouse gases as well as CO2 including methane, nitrous oxide and florinated gases. A recent UK government report suggests that these other gases emitted during 2020 had the same effect as increasing production-based CO2 emissions by 25%. I can’t find any figure for the effect on consumption-based emissions but it is likely to be similar.
A final factor is that none of these estimates includes emissions from international travel (whether aviation or shipping). A return flight to Spain emits over 1 tonne of CO2 per person so it is clearly inappropriate to leave this out of the calculation.
Which answers our questions. The figures used by the two carbon footprint calculators are so much larger because they are use consumption-based calculations and include the equivalent effect of all greenhouse gases and international travel. (The difference between the two sites is probably because the WWF site is using more recent data). In terms of which is correct, both figures are correct, but the higher figures of the footprint calculators are far more relevant if we want a true indication of how our lifestyles are affecting our environment.
There is a more sinister side to this analysis. The United Kingdom’s production-based CO2 emissions have fallen by 45% between 1990 and 2020 which might suggest we are on a trajectory to hit zero sometime in the early 2050s. In the lead in to the CoP 26 meeting in Glasgow last year, which the UK was chairing, our government used this figure quite prominently to prove its climate credentials.
Consumption based CO2 emissions by contrast have only fallen by about half this (22%). Many products that used to be manufactured within the UK leading to CO2 are not accounted for within the production-based figures, but are not included now they are manufactured overseas. This illustrates why using consumption-based figures is so importatn. If you take into account the dramatic increases in international aviation over the last 30 years, then the real decrease is almost certainly even less. An article published in the New York Times, using a slightly different dataset, suggested that UK CO2 emissions were extremely similar in 2015 to what they were in 1990 (see graph below).
On this basis the UK government would find is much more difficult to claim that it is a world leader in reducing carbon emissions. It is interesting to note that the Government stopped including consumption-based estimates in its annual reports on CO2 emissions in 2018 (see, for example, the latest such report) and now appears to focus entirely on the more flattering production-based estimates.