Earth Hasn’t Warmed This Fast in Tens of Millions of Years

• News, Chelsea Harvey,E&E (Author)

Scientists just completed one of the most comprehensive investigations of Earth’s climate history—and the findings aren’t favorable. They found that the planet could eventually warm to levels it hasn’t reached in at least 34 million years. The researchers, led by Thomas Westerhold of the University of Bremen in Germany, constructed datasets using chemical analyses of ancient sediments, drilled from the bottom of the ocean. These sediments, some of which are 66 million years old, are filled with the preserved shells of tiny organisms that can tell scientists about the temperature and chemical composition of the ocean when they were formed. Advertisement The sediments, collected from around the world over the course of many years, allowed the researchers to reconstruct Earth’s climate history going back to the mass extinction that killed three-quarters of the planet’s species, including dinosaurs. They found that the planet has passed through four distinct climate phases: warmhouse, hothouse, coolhouse and icehouse states. Transitions from one state to another have generally depended on changing greenhouse gas levels, often driven by volcanic eruptions and other natural processes, and shifts in the Earth’s orbit that affected the amount of solar energy reaching the planet. In the hottest phases, more than 50 million years ago, temperatures on Earth were more than 10 degrees Celsius hotter than they are today. But it’s important to note that it took the planet thousands or even millions of years to reach these levels—and that was long before humans ever walked the Earth. That’s in stark contrast to the kind of climate change that human activity is driving today.