I'm not sure what's done for Cap-and-Trade, when actual money might be at stake. Here's a link, which you may have seen, about how individual facility monitori

I'm not sure what's done for Cap-and-Trade, when actual money might be at stake. Here's a link, which you may have seen, about how individual facility monitoring can work, when you need quantitative flux estimates: https://ww2.arb.ca.gov/our-work/programs/methane/ab1496-research https://ww2.arb.ca.gov/our-work/programs/methane/ab1496-rese... See at the bottom -- a third-party will fly a plane in circles around the site to measure all concentrations in a surface enclosing the site. The concentrations, plus wind speed, give the site emissions. (I think that's intuitive, but it's also the divergence theorem from vector calculus.) That's a lot of work to get just one day's emissions. And there are technical issues already because you want to get the whole surface concentrations+windspeed at the same time, but you can't, because the plane has to circle the site over many hours. Despite those cautionary footnotes, this approach is used in calibration/validation of the concentration/emission relationship. Getting it all quantitatively right, as opposed to just seeing a plume, is a complex problem. People are still exploring how it can all work together (space, airborne, in situ, plus modeling).