National Geographic : 2007 Oct
has evolved. I recently had the opportunity to visit the Hub bard Glacier in Alaska. The park ranger stated that it is growing. Why is this, and how does its growth rate compare with others receding? TIM CARTER Stoughton, Wisconsin Most of the world's glaciers are thinning and receding. Few are advancing. Hubbard's atypical growth is due to the heavy snowfall it receives, a large per centage of which occurs at very high elevations. This overcom pensates for the melting and calving that occurs at its end. It seems odd that those who deny that global warming is caused by mankind claim that supporters of the concept have ulterior motives, when it is clearly evident that the naysay ers have the obvious ulterior motive: to carry on comfortable and profit-motivated lifestyles. Naysayers often claim that the warming of the Earth is a natu ral cycle and that the melting is just part of this cycle. However, it seems evident that it is more than mere coincidence that these glaciers and ice sheets have been around since long before man swung down from trees. Yet these natural fea tures of such incredible scale are melting and disappearing before our very eyes. CHRISTIAN GLENN Woodbridge, Virginia Your article warns us about the dangers of global warming caused by "cars and industry." It then tells us that the scientists who study the big thaw do so by snowmobile, truck, rocket launched satellite, helicopter, and Chilean Navy airplane. If the scientists themselves can't stop spewing petrochemical pollu tion-directly into the heart of these endangered environments, no less-why do they think any body else should or will? JOHN RUCH Boston, Massachusetts Write, Email, Fax Write National Geographic Magazine PO Box 98199 Washington, DC 20090-8199 Email firstname.lastname@example.org Fax 202-828-5460 Include name, address, and daytime telephone. Letters may be edited for clarity and length. It is what makes fire-retardant materials for the people who keep us safe. It is chemistry.