NPR logo

Revisiting The 'Keeling Curve'

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
Revisiting The 'Keeling Curve'


Revisiting The 'Keeling Curve'

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


Today's hearing had echoes of Gore's famous documentary, "An Inconvenient Truth." In that film, he talks about a graph that first got him interested in the science of global warming. The graph is called the Keeling Curve. It's named after a scientist named Charles David Keeling. It shows a continuous rise in carbon dioxide emissions in the earth's atmosphere. Back in 2007, my colleague Madeleine Brand traveled to Hawaii to find out more about Mr. Keeling.


In a way, Hawaii is the birthplace of global warming science. It's there, atop the Mauna Loa Volcano on the big island some 11,000 feet up, that Charles David Keeling went to sample the world's purest air. His research made global warming a fact, not just a theory. Now, the Keeling Curve is considered one of the most important discoveries of the 20th century, along with the DNA Helix and Darwin's Finches.

Keeling was a man obsessed with carbon dioxide. He didn't realize till much later the larger significance of his work, but it all rests on this tiny sound.

(Soundbite of air rushing into a glass flask)

BRAND: That's the sound of air rushing into a glass flask. Keeling designed that flask. It's the size and shape of a bowling ball. He'd hold it into the wind and...

(Soundbite of air rushing into a glass flask)

BRAND: Close it off. Inside, nothing but air. And then, he'd analyze that important nothingness back at the lab to find out how much CO2 was in there. Keeling would go out to gather the wind anytime he could, even on weekends. He'd bring along his young bride, Louise.

Ms. LOUISE KEELING: We went around collecting air samples, various places, when we were first married, camping out.

BRAND: You did it together?

Ms. KEELING: Yes, we did it together.

BRAND: Together, Louise and Dave - she called him by his middle name - would go on these cheap vacations, but they were really science trips.

Ms. KEELING: When we went to - we had a summer home in Montana, and even there, Dave would take air samples. I have a picture of him in his PJs going up the hill behind our place in Montana with a rucksack and the flasks, alarm clock and his tent. We were camping in a very dense area, and he was taking air samples during the night, every three hours, and he had a notebook. And in the middle of the night, and we heard this noise, and my husband turned the flashlight on, and the deer was walking away with the notebook in his mouth.

(Soundbite of laughter)

So Dave just hollered, and it was a buck, and it ran off and luckily dropped the notebook. And we have - we still have that. I think it has teeth marks in it.

(Soundbite of laughter)

BRAND: Those chewed on notebooks were among the many, many, many notebooks Keeling filled with columns of numbers.

Mr. RALPH KEELING: He didn't know what he was going to find. I think that's quite clear. No one really knew that there was going to be this simple beautiful record that emerged.

BRAND: Ralph Keeling is also a scientist. He's carrying on his dad's work.

Mr. KEELING: I think he had a sense that people were going to look back on this and say, wow, these are great records, and someone needs to do this. So he was playing for us right now, in a sense.

(Soundbite of music)

BRAND: Well, he is playing for us right now. That's Charles Keeling on a home recording.

(Soundbite of music)

Ms. KEELING: I didn't know anything about his science, but I knew he was a great musician.

BRAND: Louise was just 19 years old when she met Dave at a concert he gave at a neighbor's house. She says he could have been anything, a lawyer, an astronomer. He almost became a professional pianist.

(Soundbite of music)

BRAND: This is not a man who did things half way.

(Soundbite of music)

Ms. KEELING: His outlet was, he would sit at the piano and play for hours.

(Soundbite of music)

Ms. KEELING: I used to want to open the windows and the doors so all the neighbors would hear him play, because he was very good.

BRAND: He had a drive for perfection in piano and in science. When he was just 27 years old, he challenged his boss, Roger Revelle, a world-renowned climate scientist, about how to take carbon dioxide measurements. Revelle wanted Keeling to measure carbon dioxide the traditional way, and that meant taking air samples around the world, sort of like taking a public opinion poll of the air and take that poll, say, every 10 years to see how much the CO2 had increased.

No, no, no, said Keeling. You don't need to go all over the world because the air will come to you, better to measure in one place, one clean place, and measure every day. In 1958, Keeling set up his CO2 measuring station in the middle of the Pacific Ocean, on a dormant volcano, Mauna Loa, Hawaii. You have to drive up a twisty road among red and black volcano. It's what I imagine Mars looks like. And when I get there, wow. I can feel what Keeling must have felt. The clouds are below me.

The air is quite thin up here, and everyone who comes up here feels a little woozy and has to get their mountain legs or their volcano legs. The air is just so clean feeling, so crisp. A few scientists work here at Mauna Loa, one of them is Steve Ryan. He takes measurements once a week, exactly the same way Keeling did when he set it all up 50 years ago.

And now, Steve's going to take a measurement, a CO2 measurement...

Dr. STEVE RYAN (Scientist, National Oceanic & Atmospheric Administration, Mauna Loa): I have one of the original Keeling flasks. I'm going to open it up and take an air sample, and air will rush inside and fill it up, but I have to be careful not to contaminate it with my own breath. And then, I'm going to hold my breath, walk into the wind, and you'll hear the sound of the flask opening. Here we go.

(Soundbite of rushing air)

Dr. RYAN: There it is. We have exposed a flask.

(Soundbite of laughter)

BRAND: I can't help being amazed by how low-tech it all is. The 50-year-old flask held up to the wind, then sent by regular U.S. mail back to the mainland to be analyzed. That happens once a week. Every 10 minutes, a mechanical analyzer takes air samples inside a cinderblock building on Mauna Loa.

(Soundbite of rushing air)

BRAND: It spits out graph paper with frenetic lines on it. For years, the lines would be measured by hand, just as Keeling commanded. He insisted that his measurements be carried out exactly the same way for decades. Only last year, after his death, did the scientists feel free to switch to a computer. John Chin took the hand-made measurements for 40 years with a calculator, pencil, and ruler. Is that a ruler?

Dr. JOHN CHIN (Physicist, Mauna Loa Observatory): Yep. That's a air sample trace.

(Soundbite of laughter)


(Soundbite of laughter)

Dr. RYAN: I just did a calculation. If Johnny did this for 20 years, and every 10 minutes, you had...

Dr. CHIN: Every 10 minutes.

Dr. RYAN: Every 10 minutes that comes a little over one million data points in 20 years by hand. Amazing, isn't it?

(Soundbite of laughter)

BRAND: One million data points? Why, oh, why so much data? Was it necessary? I mean, after all, Keeling had proved his point several times over. Carbon dioxide was increasing. It had been for decades. Here's his son, Ralph.

Dr. RALPH KEELING (Program Director, Scripps CO2 Program): I think there was a sense, OK, well, you did this problem. You saw - this problem is done, why don't you move on to something else? And he was saying no. I mean, we need to keep this going. This is important.

BRAND: Keeling had to constantly fight to keep his Mauna Loa station running. Science funding tends to go with the new, not the 50-year-old measurements. The people with money in Washington wanted to know where were the discoveries, where were the exciting breakthroughs. The answer was right in front of them, right there on that line, the Keeling Curve.

At Mauna Loa, the curve is blown up on the wall. I look closely, and Steve Ryan, the scientist there, says in every dip and spike, you can see what has happened in the world over the last 50 years. What was this for?

Dr. RYAN: And then if you look at this average line, it kind of flattened out here, and that was after the collapse of the Soviet Union. So the former Soviet Empire, the economy kind of slackened off for a couple years.

BRAND: Once you hit 2000, that's a steep increase.

Dr. RYAN: Yeah. Well now, there's the China and India becoming more into first world nations.

BRAND: Becoming industrial?

Dr. RYAN: Also, fossil fuel usage is increasing.

BRAND: Back in California, at the Scripps Institution of Oceanography, Ralph Keeling now continues plotting the Keeling Curve his father began a half century ago.

Mr. KEELING: You can look at it as a beautiful scientific record, or you can look at it as an alarm bell.

BRAND: That record is responsible for our current understanding that global warming is indeed happening, and that humans are causing most of it.

Mr. KEELING: It took a while to get to the point of actually realizing that this was an alarm bell.

BRAND: And how did your dad look at it?

Mr. KEELING: I'm not sure. (Laughing) I think he was proud of it as a scientific achievement, so probably, initially, as a beautiful record.

BRAND: Charles Keeling died in 2005 at his home in Montana, where he'd go to relax. But even then - it was late spring - he couldn't resist hiking into the wilderness with his tent, his notebook, and his flasks to find out what the wind was saying.

(Soundbite of music)

COHEN: Stay with us on Day to Day from NPR News.

Copyright © 2009 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.



Please keep your community civil. All comments must follow the Community rules and terms of use, and will be moderated prior to posting. NPR reserves the right to use the comments we receive, in whole or in part, and to use the commenter's name and location, in any medium. See also the Terms of Use, Privacy Policy and Community FAQ.