The scientists can tell that this carbon influx occurred over a period of a few thousand years—a blink of an eye in geological terms—and that it had a dramatic impact on land and sea creatures. According to one of the papers presented in Bilbao, Arctic surface waters actually warmed by 9 or 10°C. The deep sea itself, long thought to be immutable, warmed by 4 or 5°C, and so did the surface temperatures of the cyclone-prone waters of the tropics. Temperatures in the middle of the big continents rose by an average of 5°C. It was a splendid time for mammals, which moved across the continents and mutated into new forms. This period of global adaptation lasted roughly 150,000 years.
Scientists don’t like to ring alarm bells unnecessarily. Nevertheless, in the last decade, the most authoritative reports on climate change have presented increasingly pessimistic worst-case scenarios about rising temperatures. For climate scientists, getting the danger across has been a challenge, to say the least. It’s difficult enough to come to grips with the fact that our actions are altering the planet’s climate system; it’s almost impossible to conceive of rethinking the engine of economic growth—fossil fuels.
Initially, scientists tended to downplay worst-case scenarios. For example, the 1995 report from the Intergovernmental Panel on Climate Change (ipcc), one of three gold-standard reports so far from the United Nations groups that draw together climate findings, postulated a global temperature rise of 3.5°C by 2100 if things got really bad. The level of the ocean, the report concluded, might rise by as much as 95 centimetres—not a great situation to be in, but not the end of civilization as we know it.
The panel’s 2001 report, which informs Al Gore’s lectures, book, and documentary An Inconvenient Truth, went further. Temperatures might increase by as much as 5.8°C, it said. Ocean levels might rise by as much as 88 centimetres, less than originally forecast—unless the Greenland ice sheets were to melt, in which case they could rise by as much as 7 metres. But this was unlikely to happen for thousands of years.
The next report, which is to be released in four parts through 2007, isn’t expected to go much further on the intensity of the shifts. Rather, it will focus on strategies to deal with the coming changes. Privately though, as their predictions about climate change begin to come true, some scientists fear that they have undersold their own findings in two ways: the changes are taking place at the most severe end of the spectrum and they are happening more quickly than many had expected. Global climate change is shaping up to be both intense and abrupt.
In his report on the economics of climate change, which was released in October 2006, Nicholas Stern stated that “prompt and strong action is clearly warranted” and that if no efforts were made to reduce emissions, there was a 50 percent chance that in the longer term the average global temperature could rise by 5°C—a radical increase “equivalent to the change in average temperatures from the last ice age to today.” So just as people are getting used to the idea that the climate is actually changing, that it’s the result of burning fossil fuels, and that the changes will likely alter life on earth as we know it, we are faced with the possibility that it will happen faster than most scientists’ own worst fears. Call it the more inconvenient truth.
We are at the Lizarraga Pass in the wild Pyrenees, part of the Navarre. The fog is heavy, and it feels chilly after the wall of wet heat in Bilbao. Horses are strolling up a mountain path, nosing the grass. Colts play. A clutch of black sheep gaze down at us.
And here is the petm boundary marker, which to me looks like dirt. There are no obvious fossils, no rocks, nothing to distinguish it. Nothing that indicates to me where it begins or ends. But the geologists and paleontologists swarm, wielding hammers and magnifying lenses. They hack away, collecting and carefully labelling samples to take back to their laboratories around the world.
They are seeing stories from the deep past in this dirt. Fifty-five million years ago, this is where land and sea met, explains Robert Speijer, a geologist at Katholieke Universiteit Leuven in Belgium. The movement of tectonic plates forced the Iberian peninsula up against Europe, bringing all of this geological evidence to the surface as the Pyrenees were created. Thanks to that, and to the farmers who likely cleared the forests here during the Middle Ages, this part of the record is now visible and relatively undisturbed.
How, I ask, do they know this is the right spot? “Well, this is the Paleocene,” Speijer says, pointing to the layer of fossil record on the other side of the dirt in question. “And that is certainly Eocene,” he says, pointing to another indistinguishable slice of earth. That means the chunk in the middle is the border between the two epochs, containing stories that could reveal much about the fate of our own world. It is not quite two metres high.
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