Think anthropogenic climate change started in the 1880s with the Industrial Revolution? Think again, a new study in the journal Nature warns.

As Chelsea Harvey explains for The Washington Post, “Using paleoclimate records from the past 500 years, the researchers show that sustained warming began to occur in both the tropical oceans and the Northern Hemisphere land masses as far back as the 1830s — and they’re saying industrial-era greenhouse gas emissions were the cause, even back then.”

People started keeping organized records on global temperatures starting around the 1880s, and most scientists look to 1880 as the start of human influence on the climate. But just looking at these records from the 1880s doesn’t tell the full story of anthropogenic climate change, lead author Nerilie Abram says.

“We can see that by only looking from the 1880s on, we don’t have the full picture of how we’ve been changing the climate,” she said.