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• 1994 Assessment
  • Cover Page
  • Authors, Contributors, and Reviewers
  • Preface
  • Executive Summary
  • Common Questions About Ozone
  • Copies and Citations
• Full Report
  • Contents, Preface, Executive Summary
  • Chapter 1
  • Chapter 2
  • Chapter 3
  • Chapter 4
  • Chapter 5
  • Chapter 6
  • Chapter 7
  • Chapter 8
  • Chapter 9
  • Chapter 10
  • Chapter 11
  • Chapter 12
  • Chapter 13
  • Common Questions About Ozone
  • Appendices

Common Questions About Ozone (4)

Scientific Assessment of Ozone Depletion: 1994
Executive Summary

World Meteorological Organization Global Ozone Research and Monitoring Project - Report No. 37

United Nations Environment Programme

World Meteorological Organization

National Oceanic and Atmospheric Administration

National Aeronautics and Space Administration

Can Changes in the Sun's Output Be Responsible for the Observed Changes in Ozone?

Stratospheric ozone is primarily created by ultraviolet (UV) light coming from the Sun, so the Sun's output affects the rate at which ozone is produced. The Sun's energy release (both as UV light and as charged particles such as electrons and protons) does vary, especially over the well-known 11-year sunspot cycle. Observations over several solar cycles (since the 1960s) show that total global ozone levels decrease by 1-2% from the maximum to the minimum of a typical cycle. Changes in the Sun's output cannot be responsible for the observed long-term changes in ozone, because these downward trends are much larger than 1-2%. Further, during the period since 1979, the Sun's energy output has gone from a maximum to a minimum in 1985 and back through another maximum in 1991, but the trend in ozone was downward throughout that time. The ozone trends presented in this and previous international scientific assessments have been obtained by evaluating the long-term changes in ozone concentrations after accounting for the solar influence (as has been done in the figure below).

Common Questions About Ozone

• Introduction
• How Can Chlorofluorocarbons (CFCs) Get to the Stratosphere If They're Heavier than Air?
• What is the Evidence that Stratospheric Ozone is Destroyed by Chlorine and Bromine?
• Does Most of the Chlorine in the Stratosphere Come from Human or Natural Sources?
• [Can Changes in the Sun's Output Be Responsible for the Observed Changes in Ozone?]
• When Did the Antarctic Ozone Hole First Appear?
• Why is the Ozone Hole Observed over Antarctica When CFCs Are Released Mainly in the Northern Hemisphere?
• Is the Depletion of the Ozone Layer Leading to an Increase in Ground-Level Ultraviolet Radiation?
• How Severe Is the Ozone Depletion Now, and Is It Expected to Get Worse?