Missing one key component

Overall, I found this article very interesting. I am constantly trying to use a systems approach to Earth science as I develop curriculum. The only reason for not giving this article 5 stars... See More

Overall, I found this article very interesting. I am constantly trying to use a systems approach to Earth science as I develop curriculum. The only reason for not giving this article 5 stars is the lack of inclusion of the cryosphere. I realize the model referenced in this article was developed by NASA, but that was in 1983! Lots of things have changed since then, and I think NASA would agree at this point that the cryosphere is an extremely important part of our Earth system. In fact, they are spending quite a lot of money on research in the Polar Regions. Just to reiterate, a very useful article, and very much the direction our Earth science, and science curriculum in general should be headed!