Answer to Question 1
Yes. As discussed in this chapter, bromine compounds used in fire extinguishers
do cause ozone depletion in the stratosphere. Bromine and chlorine behave similarly.
Answer to Question 2
There are many avenues of evidence. In historical times, we have human
descriptions in diaries and books. For earlier times, there is evidence from ice cores, from
pollen buried in lake sediments, from oxygen isotope ratios in the shells of diatoms on the
ocean floor, etc.