I think that is the root of the problem, there is no one magick trick. We need to attack it from many angles, as each of them is weighting only a couple of percents. Reduce air traffic and reduce meat consumption and reduce fossil fuel for transportation and reduce deforestation...
I had similar idea, a tool to model the economy of a country. The idea would be to give to every one a simple tool to groundcheck political programms before voting. The economy is complex, there is no simple solution to a complex problem, only trade offs. But you need to see the effect of these trade offs before making a decision and elect one or another politician.