How did global warming come about, as the experts say? Based on data averages from various reputable scientific organizations' studies (website sources), hordes of scientists (and now the author) envision the following cause and effect scenarios that may lead to a nightmarish end for all life on Earth within a few decades , unless appropriate action is made by all capable humans starting now: 1. Almost a trillion tons of greenhouse gases now blanket our planet. From 1750s to present, the world's factories, power plants, steel mills, transports, etc. have used coal and hydrocarbons as fuel. These days, their combined emissions (largely carbon dioxide or CO2) have been estimated by scientists at a low 550 billion tons to a high 1.5 trillion tons, or mid-range 720 billion tons and rising. The heat-absorbing gases have stayed within Earth's atmosphere and will likely remain for thousands or millions of years (as in planet Mars), or disappear to pre-industrial lev