I want to revisit Bill McKibben’s influential 2012 Rolling Stone article, “Global Warming’s Terrifying New Math.” I’d like us to consider where we stand today on three key issues highlighted in that piece: global temperature rise, the world’s remaining carbon budget, and the volume of fossil fuel reserves that must stay untapped to avoid dangerous warming.
2˚ Celsius:
This is the maximum global temperature increase above pre-industrial levels that scientists and policymakers have widely agreed upon to avoid the most catastrophic impacts of climate change. Crossing this threshold could lead to severe environmental, social, and economic consequences.
Now: August 2025
The world is experiencing more frequent and severe extreme weather events, and we are getting dangerously close to several climate tipping points. The current 12‑month global average temperature is 1.64°C above pre‑industrial levels. According to Copernicus Climate Service:
“The global-average temperature for the past 12 months (August 2023 – July 2024) is 0.76°C above the 1991–2020 average and 1.64°C above the 1850–1900 pre-industrial average.”
The Global Tipping Points Report warns that five major Earth systems are already at risk of crossing irreversible thresholds at today’s warming levels. These include the Greenland and West Antarctic ice sheets, thawing permafrost, widespread coral reef loss, and major changes to ocean circulation in the Labrador Sea and sub-polar North Atlantic.
Although scientists remain cautious in predicting exactly when tipping points will be crossed, the risks they pose are serious enough to demand urgent action. At the 2025 Exeter Conference on Tipping Points, scientists issued a clear call for immediate steps to address the crisis.
565 Gigatons:
This is the amount of carbon dioxide (CO2) that scientists estimated we could still emit into the atmosphere by mid-century and have a reasonable chance of staying below the 2˚C limit. It represents the remaining carbon budget that humanity has if we want to avoid the worst effects of global warming.
Now: August 2025
Human activity releases about 40 gigatons of CO₂ each year. Over the past 13 years, that adds up to around 520 gigatons, leaving only about 45 gigatons in the carbon budget if we want to stay below 1.5°C of warming. Yet, as Copernicus has already reported, global temperatures have already passed that level.
To have a 50% chance of limiting warming to 2°C, the remaining carbon budget is about 1,110 gigatons—roughly 27 years’ worth of emissions at today’s rates (as of early 2025). But at 2°C of warming, scientists warn we are very likely to cross at least one irreversible climate tipping point.
2,795 Gigatons:
This is the amount of CO2 that would be released if we burnt all the known fossil fuel reserves (oil, coal, and gas) currently held by fossil fuel companies and nations.
This number is about five times higher than the 565 gigatons we can afford to emit, meaning that the vast majority of fossil fuel reserves need to stay
Now: August 2025
If all known fossil fuel reserves were burnt, they would release about 4,777 gigatons of CO₂.
That’s 20 to 37 times more than the amount we can emit to stay below 1.5°C of warming.
And it’s 4.3 times more than what’s allowed to stay below 2°C.
This means that much of the oil, coal, and gas currently counted as assets on company balance sheets are in fact “stranded assets”—resources that cannot be used if we want to avoid a climate catastrophe.
Photo by Pixabay: https://www.pexels.com/photo/electric-towers-during-golden-hour-221012/