How Many Children Can One Oil Depot Kill?

I'm sorry if you find the title of this page offensive. Once you've read to the end, I hope you'll agree that it's fair.

In spring 2022 I witnessed protesters at an oil depot (not me) heckling the site supervisor, calling him a "child-killer". I felt bad for him.

When a friend of mine spotted the Nature paper The Mortality Cost of Carbon (https://www.nature.com/articles/s41467-021-24487-w), I realised I could use it to estimate the deaths caused by such a facility. That study estimates "that adding 4,434 metric tons of carbon dioxide in 2020 ... causes one excess death globally in expectation between 2020-2100".

However, that headline estimate is based on warming of 4.1°C by 2100. That's higher than the current best-case scenario where - if they're ever implemented - "national climate pledges combined with other mitigation measures put the world on track for a global temperature rise of 2.7°C by the end of the century", according to the UN Environment Programme's "Emissions Gap Report 2021". Fortunately, the authors include in their Table 1 a second estimate based on 2.4°C warming by 2100. In that case adding 9,318 metric tons of carbon dioxide in 2020 causes one excess death globally in expectation between 2020-2100.

The paper's estimates are worked out by considering "marginal emissions" ie what would happen if those tonnes of climate-warming gases were not emitted:

"The 2020 MCC is the number of expected temperature-related excess deaths globally from 2020 to 2100 caused by the emission of one additional metric ton of carbon-dioxide-equivalent emissions in 2020... Excess deaths are deaths attributable to climate change that occur prematurely relative to a counterfactual scenario in which the marginal emission did not occur."

Future Deaths Caused by the Oil Depot

In written evidence to court a consultant to the operator states:

  • "The pipeline generally transports in excess of 6 billion litres of product each year"
  • "The [business] stores and transports aviation fuel via pipeline to [two major] airports as well as via road tanker to others generally supplying in excess of 3.5 billion litres of product each year."

I think this means that the depot supplies 3.5 billion litres of aviation fuel each year and 2.5 billion litres of petrol and diesel.

Let's use a rough average of 2.5kgCO₂ emitted per litre of fuel burned. Then the depot facilitates the emission of 15 billion kgCO₂ each year. If "9,318 tonnes of CO₂ cause 1 future death", then:

Each year fossil fuel from this one oil depot causes 1,600 future deaths

Each day fossil fuel from this one oil depot causes 4.4 future deaths

How many of those deaths will be of children? It's somewhere between 0 and 1,600 extra dead children for each year that the oil depot operates.

By the way, the study considers only directly temperature-related deaths; there will be many more deaths that it does not cover, eg from food shortages. See Notes & Sources below.

Possible objections

"The emissions from the fossil fuels being supplied by the oil depot today are not the emissions that will cause the predicted deaths; the deaths will be caused by later emissions that take us beyond 2°C."

That's only true if we, in the present, have more right to burn the limited carbon budget than other people in the future. Unless use of fossil fuels is rapidly reduced, the planet is going to warm beyond safe levels, and all those burning fossil fuels and facilitating that, now and in the future, will share equally (in proportion to their emissions) the responsibility for the future deaths they cause.

"The study is based on tonnes of CO₂ emitted in 2020; it's now 2022."

Given that the study estimates excess deaths between 2020 and 2100, we can expect that the estimates for excess deaths caused by emissions in 2022 will be very similar.

Notes & Sources

The headline estimate in the study comes with massive error bars: the actual value of how many tonnes CO₂ causes one extra future death (if we hit 4.1°C) could be anywhere from 0 to 9,000.

The number of tonnes CO₂ causing one extra future death is highly dependent on how far we warm the planet. The authors write:

  • "The MCC are highly sensitive to future climate policy"
  • "We have shown that in the DICE baseline emissions scenario that results in 4.1°C warming by 2100, the central estimate MCC is significant. It implies that adding 4,434 metric tons of carbon dioxide in 2020 ... causes one excess death globally in expectation between 2020 and 2100."

The error bars are particularly huge because future climate policy is uncertain.

Figure 4 in the study suggests that if global warming be can limited to 2°C, there will be almost no extra deaths. Above that excess deaths climb steeply. If we hit 4.1°C, emissions linked to the oil depot each year will cause 3,400 future deaths.

Note: the study considers only directly temperature-related deaths, stating:

"the mortality damage function only represents temperature-related mortality; it leaves out potentially important climate-mortality pathways such as the effect of climate change on infectious disease, civil and interstate war, food supply, and flooding"

By "temperature-related mortality" they mean deaths caused by the wet-bulb ambient temperature.

And where did the study's authors get their data from? All reputable sources:

Credits

Thanks to my friend Alex Zeffertt for alerting me to this study.



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