A new discussion paper by former senior NASA climate scientist James Hansen and 11 other experts published in the Earth System Dynamics journal reveals the steady rise of Earth’s temperatures over the past 45 years means the planet is now as warm as it was during the interglacial Eemian period, which ended more than 115,000 years ago. Back then, Earth’s sea levels were 20-30 feet higher than they are today and there was “much less ice,” The Guardian reported.

While this paper has yet to be peer reviewed, its findings become all the more alarming when paired with the National Oceanic and Atmospheric Administration’s latest warning. Last week, the NOAA said that carbon dioxide levels “will not drop below the symbolic 400 parts per million (ppm) mark in our lifetimes--the highest concentration of CO2 since the Pliocene era 3 million years ago,” The Guardian reported.

In the Pliocene era, sea levels were a whopping 65 feet higher than they are today and there was so little ice near the north pole that trees were able to grow. Those conditions, NOAA scientist Bruce Bauer said, are a “bellwether for what future climate might be like.”