New research led by scientists at the Australian National University's Research School of Earth suggests that humans first started to significantly change the climate in the 1830s, near the beginning of the Industrial Revolution. The findings have been published in the journal Nature, and "were based on natural records of climate variation in the world's oceans and continents, including those found in corals, ice cores, tree rings and the changing chemistry of stalagmites in caves." Sydney Morning Herald reports: "Nerilie Abram, another of the lead authors and an associate professor at the Australian National University's Research School of Earth Sciences, said greenhouse gas levels rose from about 280 parts per million in the 1830s to about 295 ppm by the end of that century. They now exceed 400 ppm. Understanding how humans were already altering the composition of the atmosphere through the 19th century means the warming is closer to the 1.5 to 2 degrees target agreed at last year's Paris climate summit than most people realize." "It was one of those moments where science really surprised us," says Abram. "But the results were clear. The climate warming we are witnessing today started about 180 years ago."