Block · one region of the page, as the scanner read it. It may hold a whole story, part of one, several, or an advertisement; stitching blocks into articles is the next step. Text is supplied OCR.
Page 5 · column 1 of 6 · from the scan, no model involved
Global warming is becoming
the center of intense debate over what action, if any, it calls for. Here’s what we know for sure:
Earth’s energy comes from the sun. Some sunlight is reflected back into space by clouds or snow, but most passes through the atmosphere and warms Earth’s surface. Infra-red rays carry an equal amount of heat back into space, stabilizing Earth’s temperature. Our atmosphere contains small quantities of “greenhouse” gases (GHGs) - principally carbon dioxide (C02), methane and water vapor - which allow sunlight in, but impede infra-red outflow, acting like glass in a greenhouse. Thus, some heat is trapped, making Earth habitable. Adding atmospheric GHGs leads to increased surface warming — “global warming” - sufficient to force out enough heat through the denser GHG blanket to maintain balance.
Earth’s average temperature has varied slowly - by 8 to 10 degrees Fahrenheit - over several 100,000-year cycles, caused by gradual fluctuations in the Earth’s orbit, volcanoes and other natural phenomena, including
89.3%