It is said the reason the USS Yorktown survived the Battle of the Coral Sea was because of a chemical that is as common as the air we breath. This chemical saved many aircraft carriers and airplanes during WWII (and consequently lives). The chemical is also of grave concern to us today because elevation of this chemical has been increasing since the 1960's. Yet historical data show that this chemical always increase and decrease in a ~ 20,000 year cycle.