TEMPERATURE RISING
A Scientist, His Work and a Climate Reckoning

Jonathan Kingston/Aurora Select, for The New York Times
Published: December 21, 2010

MAUNA LOA OBSERVATORY, Hawaii — Two gray machines sit inside a pair of utilitarian buildings here, sniffing the fresh breezes that blow across thousands of miles of ocean. But once an hour, they spit out a number, and for decades, it has been rising relentlessly.

The first machine of this type was installed on Mauna Loa in the 1950s at the behest of Charles David Keeling, a scientist from San Diego. His resulting discovery, of the increasing level of carbon dioxide in the atmosphere, transformed the scientific understanding of humanity’s relationship with the earth. A graph of his findings is inscribed on a wall in Washington as one of the great achievements of modern science.

Yet, five years after Dr. Keeling’s death, his discovery is a focus not of celebration but of conflict. It has become the touchstone of a worldwide political debate over global warming.

When Dr. Keeling, as a young researcher, became the first person in the world to develop an accurate technique for measuring carbon dioxide in the air, the amount he discovered was 310 parts per million. That means every million pints of air, for example, contained 310 pints of carbon dioxide.

By 2005, the year he died, the number had risen to 380 parts per million. Sometime in the next few years it is expected to pass 400. Without stronger action to limit emissions, the number could pass 560 before the end of the century, double what it was before the Industrial Revolution.

The greatest question in climate science is: What will that do to the temperature of the earth?

Scientists have long known that carbon dioxide traps heat at the surface of the planet. They cite growing evidence that the inexorable rise of the gas is altering the climate in ways that threaten human welfare.

Fossil fuel emissions, they say, are like a runaway train, hurtling the world’s citizens toward a stone wall — a carbon dioxide level that, over time, will cause profound changes.

The risks include melting ice sheets, rising seas, more droughts and heat waves, more flash floods, worse storms, extinction of many plants and animals, depletion of sea life and — perhaps most important — difficulty in producing an adequate supply of food. Many of these changes are taking place at a modest level already, the scientists say, but are expected to intensify.

Reacting to such warnings, President George Bush committed the United States in 1992 to limiting its emissions of greenhouse gases, especially carbon dioxide. Scores of other nations made the same pledge, in a treaty that was long on promises and short on specifics.

But in 1998, when it came time to commit to details in a document known as the Kyoto Protocol, Congress balked. Many countries did ratify the protocol, but it had only a limited effect, and the past decade has seen little additional progress in controlling emissions.

Many countries are reluctant to commit themselves to tough emission limits, fearing that doing so will hurt economic growth. International climate talks in Cancún, Mexico, this month ended with only modest progress. The Obama administration, which came into office pledging to limit emissions in the United States, scaled back its ambitions after climate and energy legislation died in the Senate this year.

Challengers have mounted a vigorous assault on the science of climate change. Polls indicate that the public has grown more doubtful about that science. Some of the Republicans who will take control of the House of Representatives in January have promised to subject climate researchers to a season of new scrutiny.

One of them is Representative Dana Rohrabacher, Republican of California. In a recent Congressional hearing on global warming, he said, “The CO2 levels in the atmosphere are rather undramatic.”

But most scientists trained in the physics of the atmosphere have a different reaction to the increase.

“I find it shocking,” said Pieter P. Tans, who runs the government monitoring program of which the Mauna Loa Observatory is a part. “We really are in a predicament here, and it’s getting worse every year.”

As the political debate drags on, the mute gray boxes atop Mauna Loa keep spitting out their numbers, providing a reality check: not only is the carbon dioxide level rising relentlessly, but the pace of that rise is accelerating over time.

“Nature doesn’t care how hard we tried,” Jeffrey D. Sachs, the Columbia University economist, said at a recent seminar. “Nature cares how high the parts per million mount. This is running away.”

A Passion for Precision

Perhaps the biggest reason the world learned of the risk of global warming was the unusual personality of a single American scientist.

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