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Global Warming’s Terrifying New Math, Bill McKibben

The First Number: 2° Celsius

So far, we’ve raised the average temperature of the planet just under 0.8 degrees Celsius, and that has caused far more damage than most scientists expected. (A third of summer sea ice in the Arctic is gone, the oceans are 30 percent more acidic, and since warm air holds more water vapor than cold, the atmosphere over the oceans is a shocking five percent wetter, loading the dice for devastating floods.) Given those impacts, in fact, many scientists have come to think that two degrees is far too lenient a target. “Any number much above one degree involves a gamble,” writes Kerry Emanuel of MIT, a leading authority on hurricanes, “and the odds become less and less favorable as the temperature goes up.” Thomas Lovejoy, once the World Bank’s chief biodiversity adviser, puts it like this: “If we’re seeing what we’re seeing today at 0.8 degrees Celsius, two degrees is simply too much.” NASA scientist James Hansen, the planet’s most prominent climatologist, is even blunter: “The target that has been talked about in international negotiations for two degrees of warming is actually a prescription for long-term disaster.” At the Copenhagen summit, a spokesman for small island nations warned that many would not survive a two-degree rise: “Some countries will flat-out disappear.” When delegates from developing nations were warned that two degrees would represent a “suicide pact” for drought-stricken Africa, many of them started chanting, “One degree, one Africa.”

The Second Number: 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. (“Reasonable,” in this case, means four chances in five, or somewhat worse odds than playing Russian roulette with a six-shooter.)

This idea of a global “carbon budget” emerged about a decade ago, as scientists began to calculate how much oil, coal and gas could still safely be burned. Since we’ve increased the Earth’s temperature by 0.8 degrees so far, we’re currently less than halfway to the target. But, in fact, computer models calculate that even if we stopped increasing CO₂ now, the temperature would likely still rise another 0.8 degrees, as previously released carbon continues to overheat the atmosphere. That means we’re already three-quarters of the way to the two-degree target.

The Third Number: 2,795 Gigatons

This number is the scariest of all – one that, for the first time, meshes the political and scientific dimensions of our dilemma. It was highlighted last summer by the Carbon Tracker Initiative, a team of London financial analysts and environmentalists who published a report in an effort to educate investors about the possible risks that climate change poses to their stock portfolios. The number describes the amount of carbon already contained in the proven coal and oil and gas reserves of the fossil-fuel companies, and the countries (think Venezuela or Kuwait) that act like fossil-fuel companies. In short, it’s the fossil fuel we’re currently planning to burn. And the key point is that this new number – 2,795 – is higher than 565. Five times higher.

Which is exactly why this new number, 2,795 gigatons, is such a big deal. Think of two degrees Celsius as the legal drinking limit – equivalent to the 0.08 blood-alcohol level below which you might get away with driving home. The 565 gigatons is how many drinks you could have and still stay below that limit – the six beers, say, you might consume in an evening. And the 2,795 gigatons? That’s the three 12-packs the fossil-fuel industry has on the table, already opened and ready to pour.

We have five times as much oil and coal and gas on the books as climate scientists think is safe to burn. We’d have to keep 80 percent of those reserves locked away underground to avoid that fate. Before we knew those numbers, our fate had been likely. Now, barring some massive intervention, it seems certain.

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What all these climate numbers make painfully, usefully clear is that the planet does indeed have an enemy – one far more committed to action than governments or individuals. Given this hard math, we need to view the fossil-fuel industry in a new light. It has become a rogue industry, reckless like no other force on Earth. It is Public Enemy Number One to the survival of our planetary civilization. “Lots of companies do rotten things in the course of their business – pay terrible wages, make people work in sweatshops – and we pressure them to change those practices,” says veteran anti-corporate leader Naomi Klein, who is at work on a book about the climate crisis. “But these numbers make clear that with the fossil-fuel industry, wrecking the planet is their business model. It’s what they do.”