evidence: Earth’s greenhouse gases trap heat in the atmosphere and warm the planet. The main gases responsible for the greenhouse effect include carbon dioxide, methane, nitrous oxide, and water vapor. In addition to these natural compounds, synthetic fluorinated gases also function as greenhouse gases. Different greenhouse gases have different chemical properties and are removed from the atmosphere, over time, by various processes. Carbon dioxide, for example, is absorbed by "carbon sinks" such as forests, soil, and the ocean. Fluorinated gases are only destroyed by sunlight in the far upper atmosphere. [...] The most significant gases that cause global warming via the greenhouse effect are the following: [...] The most abundant greenhouse gas overall, water vapor differs from other greenhouse gases in that changes in its atmospheric concentrations are linked not to human activities directly, but rather to the warming that results from the other greenhouse gases we emit. Warmer air holds more water. And since water vapor is a greenhouse gas, more water absorbs more heat, inducing even greater warming and perpetuating a positive feedback loop. (It’s worth noting, however, that the net impact of this feedback loop is still uncertain, as increased water vapor also increases cloud cover that reflects the sun’s energy away from the earth but holds heat in at night.)