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Red Herring & Black Swan: Climate Change Math


The traditional statistics on greenhouse gases don’t capture emissions related to trade, shipping, or international aviation. But that’s not the only reason they’re misleading.

Sixteen-year-old climate activist Greta Thunberg walked into the Houses of Parliament on April 23 with a clear message for Britain’s lawmakers: you need to do much more to prevent catastrophic climate change.

And, she added, almost as an aside: you’ve been counting wrong.

It’s worth reading her words in context. “Since 1990, the United Kingdom has achieved a 37-percent reduction of its territorial CO2 [carbon dioxide] emissions, according to the Global Carbon Project. And that does sound very impressive. But these numbers do not include emissions from aviation, shipping, and those associated with imports and exports. If these numbers are included the reduction is around 10 percent since 1990—or an average of 0.4 percent a year.”

Thunberg was citing numbers from a Manchester research institute. She might also have quoted the United Kingdom’s Office for National Statistics, whose provisional estimates “suggest that in 2018, total UK greenhouse gas emissions were 43.5 percent lower than in 1990.” This figure, too, ignores emissions from international shipping (2.6 percent of the global greenhouse gas emissions total, according to the OECD) and aviation (2.0 percent of global CO2 emissions according to the UN). And it leaves out the emissions embodied in imported goods—obviously, if a coal-powered factory shuts down in Britain and is replaced by a similar factory in China, it’s not doing the climate any good.

Cooking the Books?

What’s going on here? Are the British government and the Global Carbon Project, which Thunberg quotes, cooking the books?

No. National emissions inventories conducted under the UN Framework Convention on Climate Change only consider emissions that occur within the borders of a given country, leaving responsibility for trade-related emissions with the exporting nation.

In fact, the so-called emission outsourcing that Thunberg is referring to has been less of a problem in Britain over the last decade. Analysis by Zeke Hausfather for Carbon Brief shows that while “domestic emissions reductions were largely offset by increased CO2 embodied in imported goods until the mid-2000s, reductions since around 2007 have not been offset by CO2 in imported goods.”

Emission-counters simply have to make decisions: we need some sort of national figures as a way to understand the global figures. And sometimes numerical inconsistency is unavoidable. Sharp readers may have noticed that this article uses CO2 emissions for shipping and greenhouse gas emissions for aviation. That’s simply how the two most authoritative organizations track the damage caused by those sectors. (CO2 is the most common heat-trapping greenhouse gas, but others, such as the methane that comes from cow belches or the hydrofluorocarbons that come from refrigeration, are more potent.)

Missing the Forest

Nevertheless, intentionally or not, the 37 percent reduction figure is misleading, for two reasons. First, because it does not accurately measure the greenhouse gas emissions for which the UK’s inhabitants are ultimately responsible. Uncounted emissions are becoming more important in general. As a report by the German Öko Institut points out, transport demand in today’s globalized world is growing so fast that international aviation and maritime transport could account for almost 40 percent of global CO2 emissions by 2050 unless drastic action is taken.

That’s partly because the world is having more success plucking low-hanging fruit, such as promoting sales of hybrid cars, than improving already-efficient airplanes. That’s fine. It makes sense to begin with measures that interfere less with economic growth. But more disruptive regulation and behavioral changes are essential if the world is to have a chance of getting a grip on climate change.

The second reason the UK’s national emission figure is misleading is because, well, it’s national. The UK could stop burning fossil fuels tomorrow, and the rest of the world, barring a rapid energy transformation, would do more than enough to ensure that the British also suffered from heat waves, crop failures, rising sea levels, and the associated economic chaos and disaster-induced migration. The British government is committed to the Paris Agreement and spends £1 billion a year on foreign aid for combating climate change—a good start, with much more to be done.

Again, one need not single out the UK for special criticism. Unlike Vladimir Putin or Donald Trump, Theresa May at least acknowledges the science; British emissions have fallen as global emissions have risen, with particularly strong progress in the electricity sector. Yet this is still not enough for Britain to meet its own targets for the next decade.

Thunberg Goes Global

For some politicians, gloomy interventions like Thunberg’s are unwelcome—UK energy minister Claire Perry expressed skepticism about the Extinction Rebellion protests that have rocked London this spring, worrying they were leaving people “fearful for the future rather than hopeful.”

Debating activists’ tactics is all well and good, but it’s undeniably counter-productive to be too self-congratulatory about falling national emissions when tracking an existential threat that demands global cooperation.
Thunberg, then, is making a factually accurate and important point about the red herring that is national, production-based emission statistics. She also follows her own logic, speaking not only to Swedish schoolchildren or the UK parliament, but also to international organizations like the EU and the UN.

Her point is: however you’re counting, the numbers don’t add up.