David Biello in Scientific American:
Roughly 251 million years ago, an estimated 70 percent of land plants and animals died, along with 84 percent of ocean organisms—an event known as the end Permian extinction. The cause is unknown but it is known that this period was also an extremely warm one. A new analysis of the temperature and fossil records over the past 520 million years reveals that the end of the Permian is not alone in this association: global warming is consistently associated with planetwide die-offs.
“There have been three major greenhouse phases in the time period we analyzed and the peaks in temperature of each coincide with mass extinctions,” says ecologist Peter Mayhew of the University of York in England, who led the research examining the fossil and temperature records. “The fossil record and temperature data sets already existed but nobody had looked at the relationships between them.”
Pairing these data—the relative number of different shallow sea organisms extant during a given time period and the record of temperature encased in the varying levels of oxygen isotopes in their shells over 10 million year intervals—reveals that eras with relatively high concentrations of greenhouse gases bode ill for the number of species on Earth. “The rule appears to be that greenhouse worlds adversely affect biodiversity,” Mayhew says.