"For each degree centigrade of warmer temperature, it is predicted that 10 percent of all known species will disappear," Djoghlaf told Reuters. "Therefore this idea of stabilizing the temperature at no more than 2 Celsius…will lead to the disappearance of 20 percent of known species," he said. "Climate change is contributing to the loss of biodiversity."

While you're guessing, why not 25 percent or 50 percent?  For that matter, why not one percent, none or an increase in species by five percent?  Perhaps climate change will motivate further diversification.  I mean, if we are all just guessing, why not tailor predictions in a more interesting manner?