Geoscience Reference
In-Depth Information
would be much warmer than they are today, the higher latitudes would be much colder, and the sea-
sons would be very much more marked. Instead, the Earth's oceans damp down the sun's ardour.
All through the summer, the oceans soak up sunlight. Unlike land, the oceans are pretty much
transparent, so the sun's rays can penetrate deep into the interior. Also, the ocean's currents keep water
moving. Warm surface water is replaced by cold water rising up from the deep to take its place in the
sun. The oceans work like a vast storage heater: they absorb heat throughout the summer, and then
slowly release it during the winter. That's why seasonal changes are so much more extreme in the
middle of continents than they are at the margins. Places like Nebraska or central Siberia are too far
from the ocean to benefit from its summer cooling and winter warming.
But on the Snowball, all that would have changed. According to Jim's model, the whole place
would have been like Nebraska or Siberia. With ice covering the oceans, there would have been no
more of this gentle amelioration of the seasons. And here's the key point: that argument would apply
right down to the tropics. Even places just a short distance from the equator would have had exagger-
ated seasons. The Flinders Ranges of South Australia would have experienced a temperature differen-
ce between winter and summer of perhaps 30 degrees C. And though the annual average temperature
would have been bitterly cold, summer temperatures could even have crept up above freezing for a
few brief months of the year. Bingo. There's your freeze and thaw. There's your explanation for the
sand wedges.
6
George Williams still believes in his Big Tilt, but most other researchers have begun to edge away
from it. The Snowball, it seemed, had survived yet another test. But Linda and Nick were still work-
ing on finding an alternative idea, one that was less wacky that George's and less extreme than Paul's.
Nick's final e-mail to Paul, back when they were still—just about—speaking, had contained this jaunty
assurance: “In parallel with an effort to develop good tests, I also accept your challenge to seek a better
hypothesis.” And that's exactly what Nick did. He and Linda teamed up with an Australian researcher
and longtime collaborator of Nick's, Martin Kennedy. And by the end of 2000, it was beginning to
look as if they were on to something.
