2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Hendrik Averkamp (1585-1634). The pleasures of winter.
Temperature changes in the 20th century covered 98 percent of the Earth's surface for the first time in the last two thousand years, according to articles published in Nature and Nature Geoscience. Before this, warming and cooling took place in different regions of the planet at different times, that is, climatic changes were not global, the authors found out.
Over the past two thousand years, several epochs of sharp climatic fluctuations have been known. This is, for example, the Little Ice Age, which lasted from about 1300 to 1850. In the past few decades, this term has often been used to refer to a prolonged cold snap on an almost planetary scale. Less well known is the Medieval Warm Period (Medieval Climatic Optimum), which lasted from 800 to 1200. In the first centuries of our era, the Roman climatic optimum occurred - a relatively short period of warming, followed by a cold snap in the early Middle Ages, which lasted until about 750.
Climatologist Raphael Neukom from the University of Bern and colleagues from the PAGES 2K consortium, whose members are engaged in paleoclimatic reconstruction, decided to test the hypothesis whether these and other climatic changes over the past 2 thousand years have occurred on a global scale. The researchers used seven statistical models to plot temperature reconstructions from AD 1 to AD 2000 using data collected by the consortium. These included written evidence, the ratio of oxygen and hydrogen isotopes in lacustrine and marine sediments, glaciological data, tree rings, the composition of fossil corals and speleotherms (carbonate formations in caves).
Analysis of the data showed that until the 20th century, all climatic changes did not occur simultaneously on the entire planet. Warming and cold snaps occurred in different regions at different times. 84 percent of the 51-year warming or cooling peaks occurred in less than half of the world's regions. Thus, during the Little Ice Age, the greatest decrease in the temperature of the earth's surface in the central and northern Pacific region, apparently, occurred in the 15th century, in northwestern Europe and northeastern North America, the peak of cooling occurred in the 17th century, and in the rest regions - at the beginning of the 19th century.
At the same time, in the 20th century, temperature increases occurred on 98 percent of the planet's surface, with the exception of the interior of Antarctica. Scientists saw two long-term periods of warming. One began at the beginning of the 20th century and, according to the authors, was the result of anthropogenic impact and natural anomalies. The second, modern period, began in the mid-1970s and continues to this day. The temperature trends observed in the 20th century have already gone beyond the temperature changes in the pre-industrial periods. According to the authors, this indicates that the current climate changes are caused by anthropogenic impact.
Change in average temperature on the Earth's surface over the past two thousand years. Computer simulation data obtained using various statistical methods. They are superimposed on instrumental data (black line) for the years 1850-2017.
Change in average temperature on the Earth's surface over the past two thousand years. Computer simulation data obtained using various statistical methods.
“This article should finally stop people who argue that current climate change is part of the climate cycle. This article shows the really big difference between past climate change and global anthropogenic impacts,”said non-study climatologist Mark Maslin of University College London.
Recently, climatologists using computer simulations showed that the concentration of carbon dioxide in the Earth's atmosphere reached a maximum in the last three million years, and the global average temperature in 2018 exceeded the average temperature for 1850-1900 by 0, 99 ± 0, 13 degrees Celsius.