A Swedish study found that the planet was warmer in ancient Roman times and the Middle Ages than today, challenging the mainstream idea that man-made greenhouse gas emissions are the main drivers of global warming.
The study, by scientist Leif Kullman, analyzed 455 “radiocarbon-dated mega-fossils” in the Scandes mountains and found that tree lines for different species of trees were higher during the Roman and Medieval times than they are today. Not only that, but the temperatures were higher as well.
“Historical tree line positions are viewed in relation to early 21st century equivalents, and indicate that tree line elevations attained during the past century and in association with modern climate warming are highly unusual, but not unique, phenomena from the perspective of the past 4,800 years,” Kullman found. “Prior to that, the pine tree line (and summer temperatures) was consistently higher than present, as it was also during the Roman and Medieval periods.”
Kullman also wrote that “summer temperatures during the early Holocene thermal optimum may have been 2.3°C higher than present.” The “Holocene thermal optimum was a warm period that occurred between 9,000 and 5,000 years ago. This warm period was followed by a gradual cooling period.”
According to Kullman, the temperature spikes were during the Roman and Medieval warming periods “were succeeded by a distinct tree line/temperature dip, broadly corresponding to the Little Ice Age.”