National Geographic reports about a new study that found the current global warming period is the longest in 1,200 years. They studied three rings, ice cores, fossils and other "proxy climate records" from 14 sites around the globe and conclude the present warming period has lasted longer and affects a broader area than any other such period in the last 1,200 years.
The team limited its study to the Northern Hemisphere during the last 1,200 years, for which there are relatively rich proxy climate data.
"We found that between [A.D.] 890 and 1170, there was statistically significant widespread warmth corresponding approximately to the so-called Medieval Warm Period," Osborn said.
However, the most widespread warmth was found not in the Middle Ages but during the 20th century.
The team says by now almost the entire Northern Hemisphere is warmer than normal.