Cutting Carbon Emissions Is Harder Than the Glasgow Climate Pact Thinks

The COP26 demands that we reduce global emissions by two-fifths in just nine years

2 min read

Three months ago the Glasgow Climate Pact (COP26) declared that by 2030 the world must cut total carbon dioxide emissions by 50 percent relative to the 2010 level, which was 30.4 billion tonnes. This would bring annual emissions to less than 20 billion tonnes, a level last seen more than 30 years ago.

What are the chances of that? Let’s look at the arithmetic.

First, assume that all energy-consuming sectors share the cuts equally and that global energy demand stays constant (instead of increasing by 2 percent a year, as it did in the prepandemic decade). Today our best commercial batteries have energy densities of about 300 watt-hours per kilogram, less than 3 percent as much as kerosene; among some 25,000 planes in the global commercial fleet, there is not a single high-capacity electric or hydrogen-powered aircraft. A 50 percent cut in kerosene-fueled flying would mean that by 2030 we would have to build about 12,000 new airplanes with capacities of from 100 people (the Embraer 190) to 400 people (the Boeing 777-300ER), all powered by as-yet-nonexistent superbatteries or equally nonexistent hydrogen systems. That’s what we’d need to fly about 2.2 billion passengers a year, for a total of about 4.3 trillion carbon-free passenger-kilometers. What are the chances of that?

In 2019 the world produced 1.28 billion tonnes of pig (cast) iron in blast furnaces fueled with coke made from metallurgical coal. That pig iron was charged into basic oxygen furnaces to make about 72 percent of the world’s steel (the rest comes mostly from electric arc furnaces melting scrap metal). Today there is not a single commercial steel-making plant that reduces iron ores by hydrogen. Moreover, nearly all hydrogen is now produced by the reforming of natural gas, and zero-carbon iron would require mass-scale electrolysis of water powered by renewable energies, something we still haven't got. A 50 percent cut of today’s carbon dependence would mean that by 2030 we would have to smelt more than 640 million tonnes of iron–more than the annual output of all of the blast furnaces outside China–-by using green hydrogen instead of coke. What are the chances of that?

Decarbonizing the global fleet of cars by 50 percent in nine years would require that we manufacture 63 million EVs a year, nearly as much as the total global production of all cars in 2019.

In 2021 there were some 1.4 billion motor vehicles on the road, of which no more than 1 percent were electric. Even if the global road fleet were to stop growing, decarbonizing 50 percent of it by 2030 would require that we manufacture about 600 million new electric passenger vehicles in nine years—that’s about 66 million a year, more than the total global production of all cars in 2019. In addition, the electricity to run those cars would have to come from zero-carbon sources. What are the chances of that?

To set goals that correspond to available technical capabilities while taking into account reasonable advances in the production and adoption of non-carbon energy sources, we must start with grade-school algebra. What are the chances of that?

This article appears in the February 2022 print issue as “Decarbonization Algebra.”

The Conversation (5)
Daniel Wasser
Daniel Wasser14 Feb, 2022

I was disappointed in this editorial. While the author's numbers are fine, his argument lacks a broader view of the potential solutions to reducing carbon emissions. "Decarbonizing the global fleet of cars by 50 percent in nine years would require that we manufacture 66 million EVs a year" -- actually, no. There is more than one way of reducing carbon emissions of the global fleet by 50 percent. For instance, if the average global fleet fuel economy increased from its current 7.2 Lge/100km (32 mpg) to 3.6 Lge/100km (64 mpg) that would reduce carbon emissions by 50 percent. This is technically feasible (though politically challenging!) and much more doable than increasing EV production capacity more than 6000 percent. And note that decarbonizing via the EV route would require that the EVs be powered by carbon-free electricity generation. If you "do the math" on that, it is equally infeasible. EVs, batteries and electrolysis of water are not the only (or even the best) ways to reduce carbon emissions. I read the Spectrum opinion pieces because I expect them reflect them to be informed by a solid engineering analysis that I cannot get in other publications. This editorial did not that expectation.

Joachim Falkenhagen
Joachim Falkenhagen07 Feb, 2022

"that’s about 66 million a year, more than the total global production of all cars in 2019"

Just use a different year for comparison "Global sales of automobiles are forecast to fall to just under 70 million units in 2021, down from a peak of almost 80 million units in 2017." (googled).

If there was scarcity in production abilities, produce smaller cars, e.g. cars with half the weight and half the per-car material consumption, allowing for twice the number of cars to be made with the same input. These will also not need 500 miles-range-batteries.

Put more existing cars out of service, and the 50% target could be reached even easier.

Gary Amstutz
Gary Amstutz05 Mar, 2022

This article paints a dark and grim future without offering any solutions to our problems. Certainly there are challenges ahead of us but the good news is that Solar Panels do in fact work, Wind Generators work, Concentrated Solar works, Electric Cars work, and Green Hydrogen can be made. And so the challenge is less of a scientific problem and more of logistics problem of how to ramp up the manufacturing process, financing, and delivery process. There is a political problem in the sense that too many people are climate deniers that do not list Climate Change as a high priority or are still denying it even exists. The recent war in Ukraine if nothing else should point out how important energy independence can be and if we were all driving electric cars there would be no need to concern ourselves with obtaining oil from countries that hate us or are engaged in international war fare. Energy Independence = Renewable Energy products. Perhaps that would sell better than Climate Change prevention. Zero Emissions also means better air quality that offers a healthier environment for all. According to the Emissions Database for Global Atmospheric Research the transportation and electricity generation sectors of the economy together create about half of all GHG and we already have solutions for both. We could accomplish much by implementing the solutions we already have. Let's do it !