Methane gas is the second greatest contributor to anthropogenic climate change, and mitigating methane emissions is an important pathway to slow the rate of global warming in the coming decades. Despite this, bottom-up estimates of methane emission rates can vary significantly from measured emissions rates. This research presentation describes the efforts to identify, characterize, and measure methane emissions sources throughout the Greater Toronto Area and Southern Ontario using a variety of in situ and remote sensing methodologies, from bicycle-based in situ measurements to total column solar spectrometry observations. From these measurements waste sector methane emissions throughout the region are characterized using atmospheric measurements for the first time. Additionally, a multi-year study comparing different ground, aircraft, and satellite based landfill methane measurement methodologies is presented. Overall, this work will help improve emissions inventories to more intelligently guide methane emissions reduction efforts across Ontario.