There are a lot of natural sources of methane and the biggest human sources are oil and gas wells and some coal mines. So Europe for example tends to have low methane leakage. However that is using the current satellites, which are not able to detect smaller emission sources.

The other really big one are methane deposits in permafrost and the ocean depths, which could be released, when we reach certain temperature increases. Especially permafrost starts to release methane today, which is one of the earliest tipping points. So we really want to know when that starts to happen.

EDIT: Also methane does not stay in the atmosphere too long. So it lowering emissions would decrease temperatures relatively quickly.