According to a Mashable article, Earth's current warming trend is leading climate scientists to believe that Pliocene-like temperatures could return within the next century. The Pliocene, which occurred around three million years ago, was a time when sea levels were approximately 30 feet higher than they are today. The world was also significantly warmer at around 5 degrees Fahrenheit, or 3 degrees Celsius, higher than pre-Industrial Revolution temperatures. The article notes that the current atmosphere contains levels of CO2 that have not been seen for millions of years. This steep increase in CO2 levels is the result of human activity and the burning of fossil fuels.

If nations do not take significant measures to reduce carbon emissions, sea levels could rise tens of feet, leaving already vulnerable coastlines underwater.

Despite taking centuries or even thousands of years to fully rise, this could greatly affect both human civilization and the natural landscape we know today. The current state of the planet could set the stage for a relatively quick return to Pliocene-like climes.

"Pliocene warmth and Earth’s CO2 levels have always naturally wavered. Humans didn’t exist and wouldn’t exist for millions of years during the Pliocene – through hirsute primate ancestors were already walking around Africa at the time", Mashable explains.

While humans may not have existed during the Pliocene, its return could have devastating consequences for life as we know it. The article notes how heat waves, wildfires, and major storms are already being exacerbated by climate change, which is predicted to further worsen as average global temperatures increase.