Advanced

Changes in biologically active ultraviolet radiation reaching the Earth's surface

McKenzie, Richard L.; Aucamp, Pieter J.; Bais, Alkiviades F.; Björn, Lars Olof LU and Ilyas, Mohammad (2007) In Photochemical and Photobiological Sciences 6(3). p.218-231
Abstract
The Montreal Protocol is working. Concentrations of major ozone-depleting substances in the

atmosphere are now decreasing, and the decline in total column amounts seen in the 1980s and 1990s at

mid-latitudes has not continued. In polar regions, there is much greater natural variability. Each spring,

large ozone holes continue to occur in Antarctica and less severe regions of depleted ozone continue to

occur in the Arctic. There is evidence that some of these changes are driven by changes in atmospheric

circulation rather than being solely attributable to reductions in ozone-depleting substances, which may

indicate a linkage to climate change. Global ozone is still lower than in the... (More)
The Montreal Protocol is working. Concentrations of major ozone-depleting substances in the

atmosphere are now decreasing, and the decline in total column amounts seen in the 1980s and 1990s at

mid-latitudes has not continued. In polar regions, there is much greater natural variability. Each spring,

large ozone holes continue to occur in Antarctica and less severe regions of depleted ozone continue to

occur in the Arctic. There is evidence that some of these changes are driven by changes in atmospheric

circulation rather than being solely attributable to reductions in ozone-depleting substances, which may

indicate a linkage to climate change. Global ozone is still lower than in the 1970s and a return to that

state is not expected for several decades. As changes in ozone impinge directly on UV radiation, elevated

UV radiation due to reduced ozone is expected to continue over that period. Long-term changes in

UV-B due to ozone depletion are difficult to verify through direct measurement, but there is strong

evidence that UV-B irradiance increased over the period of ozone depletion. At unpolluted sites in the

southern hemisphere, there is some evidence that UV-B irradiance has diminished since the late 1990s.

The availability and temporal extent of UV data have improved, and we are now able to evaluate the

changes in recent times compared with those estimated since the late 1920s, when ozone measurements

first became available. The increases in UV-B irradiance over the latter part of the 20th century have

been larger than the natural variability. There is increased evidence that aerosols have a larger effect on

surface UV-B radiation than previously thought. At some sites in the Northern Hemisphere, UV-B

irradiance may continue to increase because of continuing reductions in aerosol extinctions since the

1990s. Interactions between ozone depletion and climate change are complex and can be mediated

through changes in chemistry, radiation, and atmospheric circulation patterns. The changes can be in

both directions: ozone changes can affect climate, and climate change can affect ozone. The

observational evidence suggests that stratospheric ozone (and therefore UV-B) has responded relatively

quickly to changes in ozone-depleting substances, implying that climate interactions have not delayed

this process. Model calculations predict that at mid-latitudes a return of ozone to pre-1980 levels is

expected by the mid 21st century. However, it may take a decade or two longer in polar regions. Climate

change can also affect UV radiation through changes in cloudiness and albedo, without involving

ozone and since temperature changes over the 21st century are likely to be about 5 times greater than in

the past century. This is likely to have significant effects on future cloud, aerosol and surface reflectivity.

Consequently, unless strong mitigation measures are undertaken with respect to climate change,

profound effects on the biosphere and on the solar UV radiation received at the Earth’s surface can be

anticipated. The future remains uncertain. Ozone is expected to increase slowly over the decades ahead,

but it is not known whether ozone will return to higher levels, or lower levels, than those present prior

to the onset of ozone depletion in the 1970s. There is even greater uncertainty about future UV

radiation, since it will be additionally influenced by changes in aerosols and clouds. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Photochemical and Photobiological Sciences
volume
6
issue
3
pages
218 - 231
publisher
Royal Society of Chemistry
external identifiers
  • wos:000244739000014
ISSN
1474-9092
project
Photobiology
language
English
LU publication?
yes
id
1eaba432-3365-4a1b-99c9-cc838bd2c883 (old id 630222)
date added to LUP
2007-12-15 14:31:25
date last changed
2016-08-23 14:33:44
@article{1eaba432-3365-4a1b-99c9-cc838bd2c883,
  abstract     = {The Montreal Protocol is working. Concentrations of major ozone-depleting substances in the<br/><br>
atmosphere are now decreasing, and the decline in total column amounts seen in the 1980s and 1990s at<br/><br>
mid-latitudes has not continued. In polar regions, there is much greater natural variability. Each spring,<br/><br>
large ozone holes continue to occur in Antarctica and less severe regions of depleted ozone continue to<br/><br>
occur in the Arctic. There is evidence that some of these changes are driven by changes in atmospheric<br/><br>
circulation rather than being solely attributable to reductions in ozone-depleting substances, which may<br/><br>
indicate a linkage to climate change. Global ozone is still lower than in the 1970s and a return to that<br/><br>
state is not expected for several decades. As changes in ozone impinge directly on UV radiation, elevated<br/><br>
UV radiation due to reduced ozone is expected to continue over that period. Long-term changes in<br/><br>
UV-B due to ozone depletion are difficult to verify through direct measurement, but there is strong<br/><br>
evidence that UV-B irradiance increased over the period of ozone depletion. At unpolluted sites in the<br/><br>
southern hemisphere, there is some evidence that UV-B irradiance has diminished since the late 1990s.<br/><br>
The availability and temporal extent of UV data have improved, and we are now able to evaluate the<br/><br>
changes in recent times compared with those estimated since the late 1920s, when ozone measurements<br/><br>
first became available. The increases in UV-B irradiance over the latter part of the 20th century have<br/><br>
been larger than the natural variability. There is increased evidence that aerosols have a larger effect on<br/><br>
surface UV-B radiation than previously thought. At some sites in the Northern Hemisphere, UV-B<br/><br>
irradiance may continue to increase because of continuing reductions in aerosol extinctions since the<br/><br>
1990s. Interactions between ozone depletion and climate change are complex and can be mediated<br/><br>
through changes in chemistry, radiation, and atmospheric circulation patterns. The changes can be in<br/><br>
both directions: ozone changes can affect climate, and climate change can affect ozone. The<br/><br>
observational evidence suggests that stratospheric ozone (and therefore UV-B) has responded relatively<br/><br>
quickly to changes in ozone-depleting substances, implying that climate interactions have not delayed<br/><br>
this process. Model calculations predict that at mid-latitudes a return of ozone to pre-1980 levels is<br/><br>
expected by the mid 21st century. However, it may take a decade or two longer in polar regions. Climate<br/><br>
change can also affect UV radiation through changes in cloudiness and albedo, without involving<br/><br>
ozone and since temperature changes over the 21st century are likely to be about 5 times greater than in<br/><br>
the past century. This is likely to have significant effects on future cloud, aerosol and surface reflectivity.<br/><br>
Consequently, unless strong mitigation measures are undertaken with respect to climate change,<br/><br>
profound effects on the biosphere and on the solar UV radiation received at the Earth’s surface can be<br/><br>
anticipated. The future remains uncertain. Ozone is expected to increase slowly over the decades ahead,<br/><br>
but it is not known whether ozone will return to higher levels, or lower levels, than those present prior<br/><br>
to the onset of ozone depletion in the 1970s. There is even greater uncertainty about future UV<br/><br>
radiation, since it will be additionally influenced by changes in aerosols and clouds.},
  author       = {McKenzie, Richard L. and Aucamp, Pieter J. and Bais, Alkiviades F. and Björn, Lars Olof and Ilyas, Mohammad},
  issn         = {1474-9092},
  language     = {eng},
  number       = {3},
  pages        = {218--231},
  publisher    = {Royal Society of Chemistry},
  series       = {Photochemical and Photobiological Sciences},
  title        = {Changes in biologically active ultraviolet radiation reaching the Earth's surface},
  volume       = {6},
  year         = {2007},
}