Climate change is happening, the only question is whether mankind will outdo nature:
252 million years ago the Earth's most severe known extinction event occured.
"96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It was the largest known mass extinction of insects. Some 57% of all biological families and 83% of all genera became extinct." (wikipedia)
"The speed of the recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until the Middle Triassic), due both to the severity of the extinction and because grim conditions returned periodically for another 5 million years." (wikipedia)