Hi Kathy - well you answered my previous question about your areas connection to agriculture! I see where you're coming from as you're debating between focusing on the MWEE part or the climate change part. I think the answer is both! We like to talk about the MWEE as not something extra or added on but instead as an approach to teaching/learning. 

The questions that you're asking a great investigative questions... they're broad enough for your students to take on, refine, and identify more specific questions that they're interested in. I think if you contextualize this MWEE within your climate unit there will be a nice natural progression. One of the resources for this course is the National Climate Assessment and there is a whole section on agriculture (direct link to that page is here).  I think that Key Message 3 - Extreme Precipitation and Soil Erosion might be a good fit for all of the ideas that you're considering above. But check out the whole thing as you might find that there is a better fit for your context. Hope this helps and looking forward to seeing this idea develop!