Becoming a Witness to Climate Change

Glass vial of air

Sanjayan is the lead scientist for The Nature Conservancy. You can follow Sanjayan on Twitter @msanjayan.

For years, I have understood the causes and consequences of climate change – intellectually at least – yet something always nagged at me. Like so many other things that we take on faith or on professional credentials, sometimes talking about climate change felt more ritual than real.

I first confronted this divide in perhaps the least convenient moment: during a David Letterman interview. David Letterman had invited me on the show and we ended up talking about climate change. He grilled me about the science and frankly, how pessimistic he was about the fate of the planet.

The whole thing shook me up tremendously – not during the chat but afterwards. I realized it was no longer enough to understand climate change intellectually. To truly believe, I had to see it first hand.

Then came my chance. I was asked to be the science contributor to a Showtime docu-series on climate change called Years of Living Dangerously. My role? To travel the around the world, meeting with top climate scientists, and asking the hardest, most frequently asked questions about climate change. I knew I had to say yes. Here was my chance to witness the evidence in person. I never guessed that my very first mission would be so illuminating.

My first filming expedition was up a 11,000-foot volcano to the Mauna Loa Observatory in Hawaii to learn about the Keeling Curve – a series of measurements that have plotted the ongoing change in concentration of carbon dioxide in Earth’s atmosphere since 1958. The Keeling Curve forms the basis for global measurement of carbon dioxide in the atmosphere and, according to recent reports U.S. budget cuts are threatening the future of the Observatory.

In the mid-1950s, a meticulous young scientist, Charles Keeling, searched the world for a place to deploy an instrument he had built to measure carbon dioxide. It had to be away from continental pollution and above the thermal inversion layer; he settled a site more than 11,000 feet up the windward slope of a Pacific volcano.

When he turned on the machine in 1958, it read 313 parts of carbon dioxide per million parts of air (PPM). As the years passed, Keeling noticed that the concentrations oscillated, cycling with the seasonal uptake by plants – most of which are in the northern hemisphere – during the summer growing months. He realized he was watching the planet breathe. The second thing he noticed was that the annual peaks of carbon dioxide were going up. Each year, the values were higher than comparable dates of the previous year. Carbon dioxide levels were rising – sharply.

Today, the Keeling Curve forms the longest continuous record of atmospheric carbon dioxide. The findings are obvious, incontrovertible and hugely influential.

During my visit, I asked the manager, a 20-year veteran, if he had ever seen the number go down. “No,” he said simply, with a hint of resignation. I asked if he despaired, but he wouldn’t answer. He was a scientist doing his job, just like Keeling. What we do with the numbers is up to the rest of us.

Before I left, he handed me a small glass vial. He had taken a bleed of air from the machine and hermetically sealed it with a metal cap – a pocket of air, captured inside the vial forever. Then he wrote the carbon dioxide concentration from that very moment.

On the vial, which now sits on my desk, is written “395.01 PPM” – the highest number on that date so far and it’s unlikely to go down in the lifetime of our grandchildren. Not long after my visit, the lab’s daylong carbon count rose above 400 for the first time.

When I look at that vial, I stop intellectualizing climate change – to me, it becomes absolutely real.

I feel it in my bones.

A version of this essay recently appeared in Nature Conservancy magazine. Watch a trailer of Showtime’s Years of Living Dangerously.


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  1. I love staying connected to you through your adventures. Thanks for writing this, Sanjayan.

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