One of the approaches to meet Canada’s GHG reduction goal is to set emission mitigation plans in mega cities. The Greater Toronto Area, is the largest mega city in Canada with a population over 6 million.  Understanding and reducing methane (CH4) emissions are of particular interest due to its high global warming potential and short life time. To set a mitigation plan, it’s important to first quantify the emissions by preparing an emission inventory. The next step is to monitor CH4 levels in the atmosphere on a regular basis to observe any trends that might follow specific mitigation policies.

In this study, we first developed a bottom-up methane emission inventory with a high spatial resolution for the GTA. Then we set up a network of four Fourier Transform Spectrometers (FTS) to regularly monitor total column abundance of CH4 as well as CO2 and CO in the GTA. The measurements are used to estimate CH4 emissions in the GTA and the results are compared with the bottom-up emission inventory value.