Three Numbers for a Sustainable Future


I’m reposting this piece from my old website because it explains our carbon budget and why it’s so important that we stay within it. It also ties in well with my recent post, We Need to Talk.

McKibbon’s approach appears simplistic, but that’s okay. The science of climate change can be overwhelming with its multitude of calculations, so concision is good.

I heard Bill McKibben speak while I was at Royal Roads. I’ve read McKibben’s work. He is the well-know author of The End of Nature and the founder of Recently he has set out to create a movement for change.

McKibben was in Vermont, and our Skype call was interrupted several times by momentary outages and power bumps. Still his message came across loud and clear.

He pointed to three numbers. The first is 2 degrees Celsius. During the 2009 Copenhagen Climate Conference, 2 degrees was identified as the bottom line: 2 degrees is the amount our temperature can increase without threatening civilization as we know it. After that, all bets are off.

The second number is 565 Gigatons. “Scientists estimate that humans can pour roughly 565 more gigatons of carbon dioxide into the atmosphere by midcentury and still have some reasonable hope of staying below two degrees” (McKibben, 2012). McKibben calls this our “global carbon budget.”

Here’s the final number, and it’s a doozy: 2,795 Gigatons. 2,795 Gigatons is the “proven oil and gas reserves of the fossil-fuel companies, and the countries…that act like fossil-fuel companies. In short, it’s the fossil fuel we’re currently planning to burn” (McKibben, 2012). In case you hadn’t noticed 2,795 Gigatons far surpasses 565 Gigatons. In fact, it is five times the number that could keep us within the 2 degree limit that would allow our civilization to survive.

2,795 Gigatons does not include new reserves as they are discovered and it doesn’t include the numbers from shale gas, but it does, quite accurately, illustrate the carbon dioxide in the current reserves held by companies like ExxonMobil, Lukoil, BP, Chevron, Shell, ConocoPhillips, Gazprom and a long list of lesser-know coal, oil and gas producers. So the bottom line is this: To stay within the “safe” 2 degree increase in temperature, 80% of all reserves would need to stay in the ground.

Although we may look at this number and it may appear very abstract, it is NOT abstract for companies like Exxon or Lukoil. “It’s figured into share prices, companies are borrowing money against it, nations are basing their budgets on the presumed returns from their patrimony” (McKibben, 2012). So — what does this mean?

At current market values, those 2,795 Gigatons represent $27 trillion. To tell industry that they must leave 80% of fossil fuels in the ground is to tell them they must give up $20 trillion in assets. Stock prices would fall; investors would bail; companies would collapse. What we forget is this: the alternative is far worse.

If you would like to read Bill McKibben’s article, “Global Warming’s Terrifying New Math,” you can read the entire article online.


McKibben, R. (2012). Global warming’s terrifying new math. Rolling Stone. Retrieved from


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