Methane has a particular molecular structure that enables it to trap more heat than carbon dioxide. however, methane does
not exist as long as carbon dioxide in the atmosphere. all of the following are sources of anthropogenic methane except:
1. ruminant digestion
ii. agricultural practices
iii. fertilizers
iv. municipal solid waste landfills
v. deforestation
vi. fossil fuel extraction

Anthropogenic sources of methane include leaks during fossil fuel mining, rice agriculture, raising livestock (cattle and sheep), and municipal landfills. Methanogens thrive in the oxygen-free (anaerobic) environment of landfills, releasing the gas in significant quantities. The gas is purposefully ignited to prevent explosion or captured for its commercial value as a fuel.

Livestock such as sheep, goats, camel, cattle, and buffalo currently account for 15 percent of the annual anthropogenic methane emissions

So from that I would guess at deforestation as that releases CO2 not methane but yeah. I go the info of google. Hope this helps :)

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.