Ancient global climate events rippled unevenly across the globe
https://www.sciencemag.org/news/2019/07/ancient-global-climate-events-rippled-unevenly-across-globe
Source: By Sid Perkins, Science Magazine.
Excerpt: In the past 2000 years, Earth has drifted in and out of extended periods of warmer- and cooler-than-normal climate, including the so-called Medieval Warm Period and the Little Ice Age. Scientists long thought that during these hot and cold spells, temperatures rose and fell in sync across the globe. In fact, Earth warmed and cooled unevenly, with different regions reaching peak high and low temperatures at different times, two new studies suggest. The one exception: Since the mid–19th century, warming trends have covered some 98% of the globe. Widespread networks of weather stations that could accurately record local temperatures didn’t exist until the last half of the 1800s. But scientists can estimate past temperatures using a variety of natural proxies. These “paleothermometers” include the widths of tree rings and the proportions of isotopes—forms of atoms such as oxygen that contain different numbers of neutrons—in glacial ice, corals, clam shells, cave deposits, and even lake sediments. ...the Little Ice Age (which most scientists say began between 1350 and 1450 before being overtaken by warming in the 1800s) was undoubtedly the longest and deepest cool spell of the past 2 millennia. Most scientists had presumed that the Little Ice Age unfolded pretty much the same everywhere, Neukom says. But his team’s new analyses, reported in Nature, reveal that’s not the case. In the central and eastern Pacific Ocean, the coldest decades of the Little Ice Age fell during the 15th century. In northwestern Europe and the southeastern United States, the deepest cold occurred during the 17th century. For the rest of the world, the strongest chill didn’t occur until the mid–19th century, almost at the very end of this colder-than-normal interval. ...The results show the current global warming is unusual not only in magnitude, but also in terms of its geography, says Scott St. George, a paleoclimatologist at the University of Minnesota in Minneapolis.... “No matter where you go, you can’t avoid the dramatic march toward warmer temperatures.”....
Source: By Sid Perkins, Science Magazine.
Excerpt: In the past 2000 years, Earth has drifted in and out of extended periods of warmer- and cooler-than-normal climate, including the so-called Medieval Warm Period and the Little Ice Age. Scientists long thought that during these hot and cold spells, temperatures rose and fell in sync across the globe. In fact, Earth warmed and cooled unevenly, with different regions reaching peak high and low temperatures at different times, two new studies suggest. The one exception: Since the mid–19th century, warming trends have covered some 98% of the globe. Widespread networks of weather stations that could accurately record local temperatures didn’t exist until the last half of the 1800s. But scientists can estimate past temperatures using a variety of natural proxies. These “paleothermometers” include the widths of tree rings and the proportions of isotopes—forms of atoms such as oxygen that contain different numbers of neutrons—in glacial ice, corals, clam shells, cave deposits, and even lake sediments. ...the Little Ice Age (which most scientists say began between 1350 and 1450 before being overtaken by warming in the 1800s) was undoubtedly the longest and deepest cool spell of the past 2 millennia. Most scientists had presumed that the Little Ice Age unfolded pretty much the same everywhere, Neukom says. But his team’s new analyses, reported in Nature, reveal that’s not the case. In the central and eastern Pacific Ocean, the coldest decades of the Little Ice Age fell during the 15th century. In northwestern Europe and the southeastern United States, the deepest cold occurred during the 17th century. For the rest of the world, the strongest chill didn’t occur until the mid–19th century, almost at the very end of this colder-than-normal interval. ...The results show the current global warming is unusual not only in magnitude, but also in terms of its geography, says Scott St. George, a paleoclimatologist at the University of Minnesota in Minneapolis.... “No matter where you go, you can’t avoid the dramatic march toward warmer temperatures.”....