Two gray machines sit inside a pair of utilitarian buildings here, sniffing the fresh breezes that blow across thousands of miles of ocean.
They make no noise. 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 humanitys 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. Keelings 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.