Frequently Asked Questions

• What sort of natural variations does the ozone layer show?

  Over the UK stratospheric ozone has a strong seasonal cycle with a Spring maximum and Autumn minimum.

  During a year typical daily values can vary between 240 and 400 DU and changes of 30% over a few days are not uncommon. Over the last 35 years ozone has declined about 0.5 Du/year with the largest declines in the Spring. However, there has been little change in stratospheric ozone over the last 10 years.