Water vapor is the most abundant greenhouse gas so it is the main cause of recent global warming
Water vapor is fundamentally different from the other greenhouse gasses which directly cause global warming. It leaves the atmosphere in a matter of days and its atmospheric concentration is ultimately governed by temperature. It is critical for the natural greenhouse effect, but it is a negligible contributor to the enhanced greenhouse effect. We already know, beyond any reasonable doubt, that human emissions of the other greenhouse gasses is the primary cause of global warming.