Earth reached a new geologic epoch in the 1950s, an international scientific working group has concluded — as carbon pollution from burning fossil fuels, radioactive releases from nuclear tests and bombs, and astounding amounts of man-made substances such as fertilizers, pesticides and plastic changed the Earth’s atmosphere, land and waters.

Now, a deep lake near Toronto, Canada, with sediment deposits recording the changes, is proposed as a historic marker for the start of the Anthropocene epoch, a potential new chapter in Earth’s history.

This evidence of humans’ ability to transform the environment should also serve as a warning: With power comes a responsibility to address the consequences of human activity, including global warming.