Whether or not you agree with Bill McKibben‘s assessment that “the enemy” in the struggle to cut greenhouse gas emissions is the fossil fuel industry, I think you’ll find his new Rolling Stone essay impressive. This could be for no other reason than the three numbers he features in the piece—numbers he says “provide intellectual clarity about the greatest challenge humans have ever faced.”

2° C: The number climate negotiators have long accepted as the upper bound of acceptable global temperature rise relative to preindustrial times. The International Energy Agency recently warned that the window to hit this target, via an overhaul of the world’s energy system, is closing quickly. The aim of mitigation strategies is prevent an increase of more than 2°; we’ve already hit 0.8°.

565 gigatons: The amount of CO2 sophisticated climate models say humans could add to the atmosphere between now and midcentury and maintain, as McKibben writes, “some reasonable hope” of keeping the increase below 2°C.

2795 gigatons: The amount of CO2 that would be emitted, according to an organization called Carbon Tracker, by burning all the “proven” fossil fuel reserves now owned by public and private companies and governments. (Carbon Tracker’s website says the group is “working to align the capital markets with climate change objectives“.)

Clearly, the CO2 numbers are estimates. But the huge disparity is indeed clarifying.

(Anyone think it misleading to frame the situation this way? Please tell us how in the comments.)

Drastic numbers call for drastic analogies. Cue McKibben:

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.