Of Parts Per Million vs. Millions of Partners

The latest climate threshold we’ve crossed is no cause for celebration. But it should inspire us to reflect — and regroup.


When scientist Charles Keeling first began measuring atmospheric levels of carbon dioxide back in the late 1950s, the numbers he was getting on his instruments showed concentrations of anywhere between 310 and 316 parts of CO2 per million. As he continued to measure and record these levels over the course of decades, the steady rise that he observed in these concentrations — combined with scientists’ basic understanding of the dynamic between atmospheric carbon dioxide and atmospheric warming — led to our modern concepts of global warming and the climate change that accompanies it.

Keeling died ten years ago this June. On Wednesday, scientists at the National Oceanic and Atmospheric Administration (NOAA) paid him a mournful sort of tribute by releasing a data set confirming that humanity recently crossed an unnerving threshold. This March, for the first time since record keeping began, global atmospheric C02 levels did not fall below an average of 400 ppm for an entire month. The news came as yet another sobering reminder that human activity over the last 150 years — most notably our continuous burning of fossil fuels — has profoundly altered the physical makeup of our atmosphere.

And as Dr. Keeling and the generations of climate scientists that followed him have made clear, by fundamentally altering the chemistry of the earth’s atmosphere in this way, we have also fundamentally altered its climate, its oceans, and its plant and animal life — the entire interconnected ecosystem, that is to say, on which humans and all other organisms depend. Climate and atmospheric scientists are in agreement that we haven’t had this much carbon dioxide in our atmosphere in over 800,000 years. Lest there be any doubt as to how so much of it got there, these scientists also agree that CO2 levels have risen by 120 ppm since the advent of the Industrial Revolution. And half of this rise, they furthermore note, has taken place over the last 35 years.

It wasn’t very long ago at all that some scientists and climate advocates were coalescing around the figure of 350 ppm as the “safety threshold” below which atmospheric CO2 needed to fall were we ever to stand a chance of reversing climate change. On the one hand, then, Wednesday’s announcement by NOAA could be seen by some as a dispiriting sign.

But I don’t see it that way. In the last two decades, we’ve made extraordinary progress in slashing greenhouse-gas emissions through various means: heightening our energy efficiency, pursuing renewable energy sources, cutting pollution, and more. And later this year, world leaders will gather outside of Paris to draft what is, inarguably, the most important and urgently needed climate agreement since the phenomenon of climate change was first discovered and given a name. While Charles Keeling won’t be there to address the delegates personally, his legacy will be on full display; in a very real way his measurements and observations will serve as the scientific lingua franca for this multinational gathering.

I’ll be thinking of him, and thanking him for his dedication and meticulousness, while I’m there. And I firmly believe that when the summit is adjourned and we all return home to our respective countries, we’ll be better prepared to fight climate change at all levels — and more confident about our capacity for doing so — thanks in large part to the work that he did. Ten years after his passing, that’s the tribute that he deserves.