Industrial emissions (排放) of carbon dioxide and other planet-warming greenhouse gases have raised the global average temperature by about 0.8°C since the beginning of the Industrial Revolution. But studies have disagreed about what impact the rise is having on the world's species, says Mark Urban, an ecologist at the University of Connecticut, Storrs. Some have estimated that as many as 54% of species could eventually become extinct as a result of the climate change, but others have suggested no significant impact.①

    Such disparate result might originate from the limited nature of some individual studies, possibly because they focused only on a few species or a relatively small geographical region, says Urban.② To address these limits, Urban used statistical methods to help blend the results of previous studies into an apples-to-apples comparison that estimates the risk of extinction of species worldwide.

    ③He chose to analyze only the results of studies that had assessed extinction risks of more than one species. Then he researched into the details, such as the regions in which species considered, whether those species were limited to one small region or were widely spread, and whether the species were free to move as climate changed or were blocked by barriers such as mountain ranges or urban development.④

    Effects of climate change aren't always immediate, Urban says, and the risks of extinction he's estimated are the long-term results of species not being able to find a suitable habitat. Maybe the habitat will merely shrink to a size that can't support the species, or maybe it will disappear entirely. In some cases, he notes, a species might not be able to outpace the shift in its range, dying out before it can reach a new homeland. For over the generations that rapid warming might kill them off before they can spread to a suitable new habitat.