I do not know about iron in the mesosphere. There are many other more active gasses, elements, and processes in the mesosphere which i can imagine to be more important in the effect of climate. However, when you append the global warming as questino, i must make you realize that everything affects global warming. Its a system-> the entire atmosphere sun, galactic rays, intergalactic rays, universe. Now, the question is how much of each and how they are coupled...and what we can do about it.