SnowballEarth_590Ma 1 3 True True True True True False False False False False False False False True True True True True True True True True True True True True 1 40 False 0 7 0 0 0 0 0 0 0 0 0 0 0 0.2908 False 0 0 0 0 0 0 0 0 0 0 0 0 1.224 False 0 0 0 0 False 0 0 0 0 0 0 0 0 0 0 0 0 0 False 0 0 0 0 0 0 0 0 0 0 0 0 1285 False 0 0 0 0 0 0 0 0 0 0 0 0 none 0 0 0 123456789 1 kbasin NOV1910.rsfVaranger.A01.sC9MLD 0 0 0 0 02/11/05 0 0 0 This experiment simulates an ice age climate that occurred early in Earth's history. There is geologic evidence that this ice age was so extreme that continental ice sheets were stable in the tropics at elevations near sea level. Some hypotheses suggest that the oceans were also frozen over for up to 10 million years. In this experiment we test the impact of low levels of solar luminosity, decreased CO2, and altered paleogeography (continents, vegetation, mountains, ice sheets altered). CD8X10_V2_NoMtsNoLIce 12/31/00 G8X10_V2_NoMtsNoLIce 0 5 1 Snowball Earth: Neoproterozoic 590Ma, -6% solar, 40ppm CO2 Predict 0 0 O8X10_Varanger2_2000MLD 24 1905 otspec_Varanger.002.sC9 O8X10_Varanger2_2000MaxMLD SnowballEarth_580Ma RPLK25 RTAU.G25L15 0.9539411279525502607 REG8X10 12/01/1900 Z8X10_V2_NoMtsNoLIce V8X10_V2 Mark Chandler True False False True False 0 1 0 1900 00/00/00 Snowball Earth Varanger2_600Ma False False With the debate over global warming capturing the attention of many, it is not surprising that a great deal of current climate research is aimed at understanding the causes and effects of warmer climates. However, despite the likelihood that the 21st century will be an exceptionally warm century we are technically still in the midst of an ice age – the Pleistocene – that has persisted for nearly two million years. The Pleistocene ice age has been the focus of many climate studies that have helped us to better understand not only cold climates, but the Earth’s climate system in general. However, just as there have been periods in Earth history that were warmer even than what we expect from global warming, the Earth has experienced ice ages that were far colder than the Pleistocene. SUPER GLACIALS OF THE NEOPROTEROZOIC ERA Between 543 million and 1 billion years ago, during the Neoproterozoic Era, the Earth twice dipped into deep freezes that most geologists consider to have been among the coldest climates in the history of our planet. A variety of evidence suggests that Earth experienced two broad intervals of widespread glaciation: the first around 750 million years ago (the Sturtian glaciation) and another at approximately 580 million years before present (the Varanger or Marinoan glaciation; see Figure 1). One of the more remarkable features of these glaciations is the determination, based on the characteristics and distribution of certain sedimentary rocks and climate model results, that continent-scale ice sheets existed at sea level within 10 degrees of the equator – equivalent to the modern-day latitude of Costa Rica. Because the extreme cold conditions are thought to have produced snow and ice cover over much of the Earth's surface, the Sturtian and Varanger glaciations have become known as "snowball Earth" intervals. The possible occurrence of ice sheets in the tropics was a controversial topic until fairly recently, when data clearly supporting their existence came to light (Sohl et al., 1999). Still controversial is the question of whether the tropical oceans were also totally covered with sea ice during these extreme glacial intervals. Proponents of total or near-total freeze-over of the tropical oceans have argued that such occurrences had an enormous impact of the subsequent evolution of multicellular life on Earth, and in fact may have been the trigger for the "Cambrian explosion" of life forms that were the ancestors of much of modern multicellular life. The broader ramifications of the glaciations' effects have thus provoked a great deal of interest in understanding just what climatic conditions might have been like during the glacial intervals, and what climate forcings may have been reponsible for producing such extremely cold conditions. EdGCM Simulations of Snowball Earth Intervals Paleoclimate modeling does presen 2 Model II 1.0.6 8x10x9 False 0 0 0 0 0 0 0 0 0 0 0 0 0 0