This phenomenon is what scientists call the "greenhouse effect." Without it, scientists estimate that the average temperature on Earth would be colder by approximately 30 degrees Celsius, far too cold to sustain our current ecosystem. Second, we need to clarify the ways humans contribute to the greenhouse effect. While the greenhouse effect is an essential environmental prerequisite for life on Earth, there really can be too much of a good thing. The problem begin when human activities distort and accelerate the natural process by creating more greenhouse gases in the atmosphere than are necessary to warm the planet to an ideal temperature, for example, burning natural gas, coal and oil - including gasoline for automobile engines - raises the level of carbon dioxide in the atmosphere; some farming practices and land-use changes increase the levels of methane and nitrous oxide.