Free Astronomy Magazine January-February 2022

30 JANUARY-FEBRUARY 2022 ASTRO PUBLISHING measure an average sur- face temperature higher than 1.5 °C above previ- ous stable values, with the goal to contain the increase to within 2 °C in the next decades to avoid reaching the noto- rious “point of no re- turn.” This expression, too often interpreted as “the end of the world,” essentially concerns only mankind because the biosphere, as a whole, would be minimally affected by global warming that were to con- tinue at current rates, even up to and exceeding the levels of the mPWP. Almost all animal and plant G lobal atmospheric carbon dioxide concentrations (CO 2 ) in parts per million (ppm) for the past 800,000 years. The peaks and valleys track ice ages (low CO 2 ) and warmer interglacials (higher CO 2 ). During these cycles, CO 2 was never higher than 300 ppm. On the geologic time scale, the increase (orange dashed line) looks virtually instantaneous. Graph by NOAA (climate.gov) based on data from Lüthi, et al., 2008, via the NOAA NCEI Paleoclimatology Program. P reliminary results from a Smith- sonian Institution project led by Scott Wing and Paul Huber, showing Earth’s average surface temperature over the past 500 million years. For most of the time, global tempera- tures appear to have been too warm (red portions of line) for persis- tent polar ice caps. The most recent 50 million years are an exception. A preliminary global temperature curve shows that marine life diversi- fied in extreme heat (1) before land- based plants absorbed carbon dioxide (CO 2 ) and polar ice caps formed (2). Volcanoes and erosion swung CO 2 levels up and down (3), but mammals evolved in a warm pe- riod (4). Now, humans are rapidly warming the climate again (5). Im- age adapted from the Smithsonian National Museum of Natural History. Those phenomena are the normal and predictable consequences of the increased energy accumulated in the troposphere. Compared to the pre- industrial average values, today we This should be a real warning for humanity, which risks experiencing similar scenarios within one or two centuries if the release of CO 2 into the atmosphere is not significantly reduced. Although the phenomenon has been known for a long time, global warming seems to have become a problem only recently, due to the exacerbation of some meteorologi- cal phenomena that affect people, their assets, and their economic ac- tivities with greater violence than in the past.