evidence: A planet-wide cooling trend that began nearly 50 million years ago is reversing due to climate change, scientists report. [...] In a study published Monday in the Proceedings of the National Academy of Sciences (PNAS), scientists report that a planet-wide cooling trend that began nearly 50 million years ago is reversing due to climate change. According to the researchers, if current emission trends continue, then by 2030, Earth’s climate may resemble the mid-Pliocene epoch, which lasted from 3.3 million to three million years ago. During that period, there were no large ice sheets in the Northern Hemisphere and sea levels were about 60 feet higher than present. The epoch also marked the dawn of hominid evolution. What’s more, the researchers found that—again, if current emission trends continue—Earth’s climate could plunge further into the past. By 2150, the planet could look something like the Eocene epoch, which began just after dinosaurs went extinct and was characterized by high carbon dioxide levels, gigantic volcanic eruptions, and the advent of the ancestors of modern mammals.