During the day, the sun shines through the atmosphere, warming the earth’s surface. At night the earth's surface cools, releasing heat back into the air. But some of the heat is trapped by the greenhouse gases in the atmosphere. That's what keeps the earth’s temperature at an average 14˚C (57˚F).
The gases act like the glass walls of a greenhouse which gives it the name, greenhouse gases. Without this greenhouse effect, temperatures would drop to as low as -18˚C (-0.4˚F); too cold to sustain life on earth.
But human activities are changing earth's natural greenhouse effect with a dramatic increase in the release of greenhouse gases. Scientists agree greenhouse gases are the cause of global warming and climate change.
Since the Industrial Revolution, humans have been releasing larger amounts of greenhouse gases into the atmosphere. In the past century that amount has increased suddenly, with the effect of global warming. Global temperatures have increased in the past 30 years and are now the highest since records began.