aspect of the system, Caldeira is, at any given moment, working on four or
five disparate projects. He particularly likes computations of a
provocative or surprising nature; for example, he once calculated that
cutting down all the world’s forests and replacing them with grasslands
would have a slight cooling effect. (Grasslands, which are lighter in color
than forests, absorb less sunlight.) Other calculations of his show that to
keep pace with the present rate of temperature change, plants and
animals would have to migrate poleward by thirty feet a day, and that a
molecule of CO 2 generated by burning fossil fuels will, in the course of its
lifetime in the atmosphere, trap a hundred thousand times more heat
than was released in producing it.
At One Tree, life for Caldeira and his team revolved around the tides.
An hour before the first low tide of the day and then an hour afterward,
someone had to collect water samples out at DK-13, so named because the
Australian researcher who had set up the site, Donald Kinsey, had labeled
it with his initials. A little more than twelve hours later, the process would
be repeated, and so on, from one low tide to the next. The experiment was
slow tech rather than high tech; the idea was to measure various
properties of the water that Kinsey had measured back in the nineteen-
seventies, then compare the two sets of data and try to tease out how
calcification rates on the reef had changed in the intervening decades. In
daylight, the trip to DK-13 could be made by one person. In the dark, in
deference to the fact that “no one can hear you scream,” the rule was that
two had to go.
My first evening on One Tree, low tide fell at 8:53 PM. Caldeira was
making the post–low-tide trip, and I volunteered to go with him. At
around nine o’clock, we gathered up half a dozen sampling bottles, a pair
of flashlights, and a handheld GPS unit and started out.
From the research station, it was about a mile walk to DK-13. The
route, which someone had plugged into the GPS unit, led around the
southern tip of the island and over a slick expanse of rubble that had been
nicknamed the “algal highway.” From there it veered out onto the reef