Free Astronomy Magazine January-February 2022

31 JANUARY-FEBRUARY 2022 ASTRO PUBLISHING lion years, for example, there were at least two long heat peaks, the first of which, called the Cre- taceous Thermal Maxi- mum (CTM), occurred around 92 million years ago, while the second, known as the Paleocene- Eocene Thermal Maxi- mum (PETM), manifested itself around 55 million years ago. The geologi- cal records from those periods tell us that dur- ing the CTM, atmos- pheric carbon dioxide levels certainly rose over 1000 ppm and possibly even over 2000 ppm. At those levels, average sur- face temperatures must have been at least 5 to perhaps more than 8 de- grees Celsius higher than in the pre-industrial era (in 1750, the average temperature was close to 14 °C or 57 °F; today it is around 15.5 °C or 60 °F). Even during the CTM, sea levels were 50 to 100 me- T he amount of carbon dioxide in the atmosphere (blue line) has increased along with human emissions (gray line) since the start of the Industrial Revolution in 1750. Emissions rose slowly to about 5 billion tons per year in the mid-20 th century before skyrocketing to more than 35 billion tons per year by the end of the century. NOAA (climate.gov) graph, adapted from original by Dr. Howard Diamond (NOAA ARL). Atmospheric CO 2 data from NOAA and ETHZ. CO 2 emissions data from Our World in Data and the Global Carbon Project. D epiction of living biota during the Paleocene-Eocene Thermal Maximum, which occurred around 55 million years ago. Geological and paleontologi- cal evidence tells us that life on Earth proliferated wonderfully at that time, al- though average surface temperatures were over 5 °C higher than today. [National Geographic, Aldo Chiappe] species would adapt gradually, changing habits and behaviors. Our ancestors of the Upper Paleolithic (from 35,000 to 12,000 years ago) would certainly not have com- plained about a few more degrees of higher temperature, while for “Homo Technologicus” an average of half a degree Celsius more per century is already a drama. It should be noted that the temperatures of the mPWP were no more than sweet warmth when compared to those of previous, much warmer periods, dur- ing which life proliferated anyway and everywhere. In the last 100 mil-