New research led by Australian scientists has pegged back the timing of when humans had clearly begun to change the climate to the 1830s. The findings, published on Thursday in the journal Nature, 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. 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.
— source smh.com.au
remember safe maximum limit of CO2 is 350 ppm.