Which gas is NOT considered a major greenhouse gas?

Ozone is considered a minor greenhouse gas compared to the others listed. While ozone does play a role in the greenhouse effect, it is not classified as a major greenhouse gas in the same way that carbon dioxide, methane, and water vapor are.

Carbon dioxide and methane are significant contributors to the greenhouse effect due to their abundance and longevity in the atmosphere. Water vapor is also a primary greenhouse gas because it accounts for a large, natural portion of the greenhouse effect, and its concentration can increase in response to temperature changes. Ozone, while influential especially in the stratosphere and lower atmosphere, does not have the same overall impact as those major gases when considering their roles in global warming and climate change.

Thus, identifying ozone as not being a major greenhouse gas is accurate, as its relative concentration and the extent of its impact are less significant than that of water vapor, carbon dioxide, and methane.