In the last part of the 20th century, scientists developed the theory that the planet was warming and that the primary cause was the increasing amounts of atmospheric carbon dioxide (CO2), which are the product of burning oil, natural gas, and coal (fossil fuels). Although many climatologists believe in the so-called greenhouse effect, many others do not subscribe to this theory. Further, Earth’s temperature has increased and decreased many times in its long history. We have had higher temperatures and we have had lower temperatures, including various ice ages. In fact, a period called the ‘little ice age’ ended around the middle to the end of the nineteenth century. Then the temperature rose until about 1940, at which point it decreased until 1975. In fact, a Newsweek article published 28 April 1975, discussed the possibility of global cooling, which seemed to be the consensus among scientists at the time. There are three critical questions that need to be answered in order to resolve the issue.
a. Is Earth actually warming?