Methane gas from a human's butt that was sequestered by a cow, not burped or flatulate, that came from grass, that came from the atmosphere that came from the oceans, goes back to the atmosphere that reacts with lightening discharge that falls dissolved in rain back to the oceans, forms carbonates that are subducted by plate teutonics, released as CO2 through volcanoes and earthquakes.
Hence a net neutral carbon exchange. It does not matter where in the cycle you examine, it does not alter the carbon. The only facetious argument is where the carbon came from and where it is going.
Just like the water cycle; vapor - liquid - solid and back again. Where did the water come from and where is it going to?
By their percentage contribution to the greenhouse effect on Earth the four major gases are:
- water vapor, 36–70%
- carbon dioxide, 9–26%
- methane, 4–9%
- ozone, 3–7%
The major non-gas contributor to the Earth's greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on radiative properties of the atmosphere.
The idea of attacking carbon dioxide as the major cause of global warming is for fools who did not learn anything in science. Or, they were recently educated by our political correct institutions of higher learning.