vel climbs again," Lowe says. "It may never return to its full glorious 70 degrees Centigrade level, but it probably climbed to make the Earth warm again."Continents played key role in collapse and regeneration of Earth's early greenhouse, geologists say If a time machine could take us back 4.6 billion years to the Earth's birth, we'd see our sun shining 20 to 25 percent less brightly than today. Without an earthly greenhouse to trap the sun's energy and warm the atmosphere, our world would be a spinning ball of ice. Life may never have evolved. But life did evolve, so greenhouse gases must have been around to warm the Earth. Evidence from the geologic record indicates an abundance of the greenhouse gas carbon dioxide. Methane probably was present as well, but that greenhouse gas
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