In order to limit the global temperature rise to 1.5 degrees above pre-industrial levels in the long term – as agreed in the Paris Climate Agreement – all emissions still being produced after 2050 must continually be offset by removing carbon dioxide from the atmosphere. Options for achieving this include afforestation, bioenergy plants with carbon capture, or machines that extract the greenhouse gas directly from the air. The carbon is then stored deep underground in former oil and gas reservoirs. “However, based on realistic calculations, the sustainable long-term annual capacity of all these natural and technological CO₂ sinks amounts to less than ten percent of current annual greenhouse gas emissions,” says Julia Danzer, summarizing one of the key findings of the new study she has published together with Gottfried Kirchengast from the Wegener Center and Institute of Physics at the University of Graz. In the study, the two also analyze how globally limited emission and removal budgets can be allocated across countries that individually, and collectively as a worldwide goal, want to achieve climate neutrality.
Gaming world exposes injustice
Kirchengast and Danzer have developed a simple yet instructive “computer game model” for this purpose, which they used to explore justice aspects in such budget allocations. In a fictional “Austro-World”, they placed four stylized countries: Richland and Poorland, each with a population of three million persons; Wonderland with two million persons; and Otherland with one million. The countries have two decades to individually and collectively achieve net-zero emissions. With a carbon removal budget of, say, 100 million tonnes of CO2 – which, in a fair world, is distributed with equal shares per person – the maths is simple: Richland and Poorland each receive around 33 million tonnes, Wonderland 22 million and Otherland 11 million tonnes.
Starting from such a fair world, the researchers have examined further plausible scenarios in which the game is getting unfair – such as Richland claiming a larger emission budget at the expense of Poorland and additionally exploiting advantages in CO2 sinks. “For example, an oil-producing country can make other countries depending on it once again, after the profit from oil sales before, by its control over the empty underground reservoirs now used for carbon storage,” explains Kirchengast. The result of an unfair scenario of this kind: Richland has a sharply raised carbon removal budget of 63 million tonnes of CO2, whilst Poorland is left with only 16 million.
“Our model is deliberately simple in this initial study, but it highlights the fundamental problem. In a next step, it can be applied to real-world country data,” emphasizes Kirchengast. “But even as it stands, it is clear just how much a lax climate policy is placing a huge and extremely unfair burden on the current generation of children, given the limited capacity of sustainable CO2 sinks.” “Scaling up carbon dioxide removal to billion-ton capacities also takes a long time, whether you’re planting trees or developing new technologies,” adds Julia Danzer. “Our study shows that fairness is just as important here as it is for the urgently needed reduction of greenhouse gases within the limited emission budget.”
