The snowball Earth hypothesis: testing the limits of global change

The gradual discovery that late Neoproterozoic ice sheets extended to sea level near the equator poses a palaeoenvironmental conundrum. Was the Earth's orbital obliquity > 60° (making the tropics colder than the poles) for 4.0 billion years following the lunar‐forming impact, or did climate cool globally for some reason to the point at which runaway ice‐albedo feedback created a `snowball' Earth? The high‐obliquity hypothesis does not account for major features of the Neoproterozoic glacial record such as the abrupt onsets and terminations of discrete glacial events, their close association with large (> 10‰) negative δ 13 C shifts in seawater proxies, the deposition of strange carbonate layers (`cap…

• NS
  National Science Foundation
• NA
  National Aeronautics and Space Administration
• HU
  Harvard University