The recent United Nations IPCC (Intergovernmental Panel on Climate Change) 6^th Assessment Report has set off a frenzy of “after-market analysis” in the environmental community to help the public make sense of the scientific jargon in the report. There is no ambiguity that we must reduce emissions to a level that can be absorbed by natural systems; if greenhouse gases continue to increase in the atmosphere, the earth’s climate systems will get perilously unstable. The buzz is about what happens if we do not reduce emissions fast enough – in other words, what are the probabilities of various climate calamities under different decarbonization pathways? Glen Peters, Research Director at the Center for International Climate Research in Oslo, published the above graphic.

Each line in the graphic represents a future emissions scenario. Let’s look at the red line. In that scenario, CO₂ emissions fall starting in 2021, reach 50% reduction by about 2040 and net zero by about 2080. In this scenario, what is the total carbon budget since the start of 2020? Answer: 900 Gigatons of CO₂ (a gigaton is a billion tons) – that’s the cumulative emissions from 2020 to the end of the century. And is it possible that we will restrict global warming to 1.5^oC under this scenario? Answer: yes, but with a paltry probability of 17% and therefore unlikely. In other words, we take an 83% risk of exceeding 1.5^oC of warming and being exposed to the concomitant environmental risks.

Now turn your eye to the orange line. It aggressively reduces CO₂ much faster: 50% reduction by 2030 and net zero by 2040, in line with CURE100 goals. Accordingly, the carbon budget is only 300 Gigatons of CO₂, 1/3 of the red line that we looked at. And what is the probability of keeping warming within 1.5^oC? A good answer: 83% and therefore highly likely.

As Greta Thunberg tweeted, “This basically sums up our situation.”

Either we aggressively decarbonize and achieve a high probability of keeping warming at manageable levels, or we decarbonize at a more sedate pace  — the business-as-usual approach — but take much higher environmental risks.

What does all this have to do with roulette wheels?