It is somewhat deceptive framing, because methane can not accumulate in the atmosphere the way CO2 does. Its levels in the atmosphere will break down relatively quickly if we reduce output, unlike CO2. But the present level of methane in the atmosphere basically captures about 30% as much heat as the present level of CO2. That still leaves CO2 as significantly larger immediate problem and the much larger future problem.
We must do what we can, observing that every little counts - a little, and every lot counts a lot.
Yeah but that CO2 is already part of the ppm that is measured. And water vapor of course, has the ability to cool or heat depending on the position in the atmosphere and amount of particulates for it to condensate on (to form clouds).
No, we don't have anything close to a precise global temperature over the entire Holocene (the period you describe, that we are presently in, coinciding with the end of the most recent glacial period). We at best have spotty tree rings, ice core samples (which are inherently limited to arctic regions), and other various rough proxies which have a higher margin of error than we have observed in even the past 100 years.
Good, broadly available, consistently measured temperature data from daily mercury record keeping was mainly only really done in UK and colonial U.S. until the late 1800s. Even then most of the world did not maintain standards for temperature stations until the early to mid 20th century. Global temperature estimates that actually span the whole globe were not really possible until the weather satellite era, around the late 1970s. So there is a big problem when comparing the precision and breadth of modern temperature data with historical estimations for a number of reasons. Not least of which is that we do not really see the sample rates of historical data necessary to estimate the periodic, even as small as decadal, swings to any high degree of accuracy.
