Dr. Jonathon Foley is a former graduate of the University of Wisconsin like I am, and has spent much of his life looking at the impacts of changing climate on the earth. Here is a short and easy to read discussion of how we know climate is changing and where the greenhouse gases that are causing those changes are coming from, based on three pie charts. Note that agriculture and food production is a fairly large source but not as large as energy production and just a little larger than transportation. This is for the entire world, too, so these pie charts would look different if we just looked at the US, where agricultural production is more efficient than in many other countries. You can read it at his blog at https://globalecoguy.org/the-three-most-important-graphs-in-climate-change-e64d3f4ed76.