There’s not enough evidence to say the net zero emissions target will be missed by 49 years

“The problem is, the government’s own figures show that they are missing the carbon budget—let alone 2050, it will be 2099 before this country meets zero.”

Jeremy Corbyn, 5 February 2020

“Despite pledging to meet net zero emissions by 2050, the government are currently on track to meet that target only by 2099. Can we afford to wait another 79 years before we reach net zero in this country?”

Jeremy Corbyn, 29 January 2020

There is not enough evidence to support Jeremy Corbyn’s claim that the government will not meet its net zero emissions target until 2099—49 years later than planned. 

Labour’s claim rests on the assumption that carbon emissions will continue to reduce at the same rate they did last year. And that in 2099 emissions will finally be low enough (according to the World Wide Fund for Nature) to be offset with carbon capture initiatives.

As we’ve written before, simply drawing a line into the future has little value as a prediction or forecast. 

The net zero target aims for the UK to emit as many greenhouse gasses as it removes from the environment by 2050. Although the UK has made fast progress on cutting emissions—which have fallen 43% since 1990—we have written before it is unlikely to reach the target.

Labour’s methodology rests on uncertain assumptions

The claim, made at Prime Ministers’ Questions for the last two weeks, was originally cited by Mr Corbyn in July last year, and is based on Labour analysis of emissions rates. 

The analysis is based on two assumptions. An assumption about what level of emissions can be balanced by offsetting measures, and an assumption about when the UK will reach that level of emissions. Both are uncertain. 

On the first, Labour used a figure suggested by the WWF that 94 million tonnes of greenhouse gas emissions “is sufficiently low to be compensated for by GGR [greenhouse gas removal] and achieve net-zero emissions”. This figure is not used by the Committee on Climate Change (an independent body that advises the government) or by the government. Because Labour’s analysis only focused on carbon emissions it adjusted that 94 million tonnes of greenhouse gas (though there are some issues with using this figure which we’ll get to in a moment). Around 80% of greenhouse gases in any given year are carbon emissions, so Labour set the target as roughly 80% of the 94 million tonnes.

As for when Labour expect the UK to reach this target it took the current net CO2 emissions and assumed that the estimated 2% fall observed between 2017 and 2018 would be replicated every year. Using this method the ‘target’ in Labour’s analysis would be met by roughly the end of the century, though by our count slightly earlier than 2099.

But carbon emissions are variable and looking at the change over just one year could give a misleading impression. Carbon dioxide emissions fell by 2.9% between 2016 and 2017, and by 5.7% between 2015 and 2016. When doing the same calculation but using an average of the last three years’ reductions, the Labour analysis says the target would be met nearly 30 years sooner in 2061, illustrating the volatility of its estimate. 

A spokesperson for the Committee on Climate Change said: “Annual emissions reductions are likely to vary, and average emissions reductions in the past are not necessarily an indicator for future emissions.”

In its original analysis Labour said it was looking at when the target would be met if “progress continues at its current rate” so it doesn’t include the possibility that carbon reduction could accelerate, perhaps through advancements in new technologies, or even slow over the coming decades. 

Bad sums

Even if Labour’s methodology had been fair, it also made mistakes when doing the calculation. 

Firstly, there are issues with the figure it used when projecting forward last year’s carbon dioxide reduction.

As we mentioned the analysis Labour did was based on provisional figures for the estimated fall in carbon emissions between 2017 and 2018. In the original press release from July 2019, Labour said: “Emission reduction has slowed to a crawl in recent years, with the amount of carbon released falling only 1.5 per cent in 2018”. In the analysis we’ve seen, Labour said this was rounded to 2%.

But the provisional figures on carbon emissions didn’t say they only fell by 1.5% between 2017 and 2018. They said they fell by 2.4%.

Using the 2% rounded figure, Labour found net zero wouldn’t be achieved until 2099. If Labour had used the unrounded 2.4% figure, net zero would have been projected to have been achieved by 2086—a full 13 years earlier

The final data, published this week, shows carbon emissions fell 2.2% between 2017 and 2018.

The second problem with Labour’s sums is that they seem to have misinterpreted the findings of the WWF.

The WWF said that 94 million tonnes of greenhouse gas could be removed and so emissions of 94 million tonnes would achieve net-zero. That 94 million tonnes is a gross figure so doesn’t count any greenhouse gas removal. However, the government statistics Labour used as a starting point for its analysis are net figures, as they take into account both the current gross emissions and gross removals. 

Therefore Labour was wrong to assume that when net carbon emissions reach 80% of 94 million tonnes it would equate to net zero—their forecasting should either have measured when the UK’s net emissions are projected to reach zero or when the UK’s gross emissions are projected to reach 94 million tonnes. 

The WWF figures also include emissions from shipping and aviation, but these are omitted from the government emissions figures used by Labour for their analysis.