Twice now R Jordan in his correspondence to you has asked the question 'How does the carbon dioxide a heavy gas get to the trees?” There are at least two methods. The first is by wind and the second is by convection created by the warming of the earth by the sun causing the lighter carbon dioxide to rise and mix with the other gases. This is the same basic physics mechanisms that creates thunderstorms etc as well as global warming. This is one of the principles learned in first year physics a subject taking by almost all scientists studying for a their degree and is even part of the modern equivalent of the medical intermediate.
Professor(retired) D J Barnes PhD DIC MSc (first class hons)
BSc (all in physics) Tanners Point.