It is not emitted in similar quantities to CO2. It is remarkable that practically all of the charts of greenhouse gases show methane as a fraction already multiplied by its Global Warming Potential factor. Its sensible to present the gases already weighted, but when its not explicit enough and raw figures by weight are hard to come by - its pretty natural to do the math again and re-multiply by the GWP factor - resulting in a shocking discovery that methane is widely misunderstood or misreported.

However, global anthropogenic emission of methane is about 300 Tera-grams per year [1]. Anthropogenic emission of CO2 is about 35 Giga-tonnes per year.

300 Tera-grams is 0.3 Giga-tonnes

300 Tera-grams of CH4 degrades in about 10 years into about 0.5 Gigatonnes of CO2. About 1.5%, one sixtieth of the CO2 problem which can last hundreds of years. Methane emissions present 10-15% of the immediate and near term problem - thats less than half, less than a quarter... seriously, its about an eighth. After 10-15 years the elimination of methane, eliminates about a sixtieth of the global warming emissions problem. This will be why the IPCC presents CO2 as the major issue, because they do find and show that it is.

[1] (Table 1) http://rsta.royalsocietypublishing.org/content/roypta/369/19...