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A runaway spurt of global warming 55 million years ago turned Earth into a hothouse but how this happened remains worryingly unclear, scientists said on Monday. Previous research into this period, called the Palaeocene-Eocene Thermal Maximum, or PETM, estimates the planet's surface temperature blasted upwards by between five and nine degrees Celsius (nine and 16.2 degrees Fahrenheit) in just a few thousand years. The Arctic Ocean warmed to 23 C (73 F), or about the temperature of a lukewarm bath. How PETM happened is unclear but climatologists are eager to find out, as this could shed light on aspects of...

A rapid rise in temperature on ancient Earth triggered a climate response that may have prolonged the warming for many thousands of years, according to scientists. Their study, published online in Nature Geoscience, provides new evidence of a climate feedback that could explain the long duration of the Paleocene-Eocene Thermal Maximum (PETM), which is considered the best analogue for modern climate change. The findings also suggest that climate change today could have long-lasting impacts on global temperature even if humans are able to curb greenhouse gas emissions. "We found evidence for a feedback that occurs with rapid warming that can...

Enlarge ImageProbing the past. Dark, red-brown ocean sediment layers reveal a telltale warming episode in cores retrieved by the drill ship JOIDES Resolution (inset).Credit: J. C. Zachos; (inset) Integrated Ocean Drilling Program Carbon dioxide (CO2) gets a bad rep for contributing to global warming, and deservedly so. But scientists say they can't entirely blame the greenhouse gas for a curious spike in Earth's temperature 55 million years ago. New research reveals that something else also seems to have warmed the planet during that time, though no one's quite sure what it was. Over the past couple of decades, researchers...