scholarly journals Projections of UV radiation changes in the 21st century: impact of ozone recovery and cloud effects

2011 ◽  
Vol 11 (4) ◽  
pp. 10769-10797 ◽  
Author(s):  
A. F. Bais ◽  
K. Tourpali ◽  
A. Kazantzidis ◽  
H. Akiyoshi ◽  
S. Bekki ◽  
...  
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
High Latitudes ◽  
Northern Latitudes ◽  
Yearly Average ◽  
The 1960S ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
The Tropics

Abstract. Surface erythemal solar irradiance (UV-Ery) from 1960 to 2100 has been derived using radiative transfer calculations and projections of ozone, temperature and cloud change from 14 chemistry climate models (CCM), as part of the CCMVal-2 activity of SPARC. Our calculations show the influence of ozone depletion and recovery on erythemal irradiance. In addition, we investigate UV-Ery changes caused by climate changes due to increasing greenhouse gas concentrations. The latter include effects on both stratospheric ozone and cloud changes. The derived estimates provide a global picture of the likely changes in erythemal irradiance during the 21st century. Uncertainties arise from the assumed scenarios, different parameterizations – particularly of cloud effects on UV-Ery – and from the diversity in the CCM projections. The calculations suggest that relative to 1980 annually mean UV-Ery in the 2090s will be on average ~12% lower at high latitudes in both hemispheres, ~3% lower at mid latitudes, and marginally higher (~1%) in the tropics. The largest reduction (~16%) is projected for Antarctica in October. Cloud effects result in additional 2–3% reduction in UV-Ery at high latitudes, but they slightly moderate it at mid-latitudes (~1%). The year of return of erythemal irradiance to values of certain milestones (1965 and 1980) depends largely on the return of column ozone to the corresponding levels and is associated with large uncertainties mainly due to the spread of the model projections. The inclusion of cloud effects in the calculations has only a small effect of the return years. At mid and high latitudes, changes in clouds and stratospheric ozone dynamics due to greenhouse gases will sustain the erythemal irradiance at levels below those in 1965, despite the removal of ozone depleting substances. At high northern latitudes, the projected decreases in cloud transmittance towards the end of the 21st century will likely reduce the yearly average surface erythemal irradiance by up to 10% with respect to the 1960s.

scholarly journals Projections of UV radiation changes in the 21st century: impact of ozone recovery and cloud effects

2011 ◽  
Vol 11 (15) ◽  
pp. 7533-7545 ◽  
Author(s):  
A. F. Bais ◽  
K. Tourpali ◽  
A. Kazantzidis ◽  
H. Akiyoshi ◽  
S. Bekki ◽  
...  
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
High Latitudes ◽  
Global Circulation ◽  
Yearly Average ◽  
The 1960S ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
The Tropics

Abstract. Monthly averaged surface erythemal solar irradiance (UV-Ery) for local noon from 1960 to 2100 has been derived using radiative transfer calculations and projections of ozone, temperature and cloud change from 14 chemistry climate models (CCM), as part of the CCMVal-2 activity of SPARC. Our calculations show the influence of ozone depletion and recovery on erythemal irradiance. In addition, we investigate UV-Ery changes caused by climate change due to increasing greenhouse gas concentrations. The latter include effects of both stratospheric ozone and cloud changes. The derived estimates provide a global picture of the likely changes in erythemal irradiance during the 21st century. Uncertainties arise from the assumed scenarios, different parameterizations – particularly of cloud effects on UV-Ery – and the spread in the CCM projections. The calculations suggest that relative to 1980, annually mean UV-Ery in the 2090s will be on average ~12 % lower at high latitudes in both hemispheres, ~3 % lower at mid latitudes, and marginally higher (~1 %) in the tropics. The largest reduction (~16 %) is projected for Antarctica in October. Cloud effects are responsible for 2–3 % of the reduction in UV-Ery at high latitudes, but they slightly moderate it at mid-latitudes (~1 %). The year of return of erythemal irradiance to values of certain milestones (1965 and 1980) depends largely on the return of column ozone to the corresponding levels and is associated with large uncertainties mainly due to the spread of the model projections. The inclusion of cloud effects in the calculations has only a small effect of the return years. At mid and high latitudes, changes in clouds and stratospheric ozone transport by global circulation changes due to greenhouse gases will sustain the erythemal irradiance at levels below those in 1965, despite the removal of ozone depleting substances. At northern high latitudes (60°–90°), the projected decreases in cloud transmittance towards the end of the 21st century will reduce the yearly average surface erythemal irradiance by ~5 % with respect to the 1960s.

Comparison of observed lower stratospheric ozone changes with free-running chemistry climate models

2020 ◽  
Author(s):  
William Ball ◽  
Gabriel Chiodo ◽  
Marta Abalos ◽  
Justin Alsing
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Total Column Ozone ◽  
Free Running ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
The Tropics

<p>The ozone layer was damaged last century due to the emissions of long-lived ozone depleting substances (ODSs). Following the Montreal Protocol that banned ODSs, a reduction in total column ozone (TCO) ceased in the late 1990s. Today, ozone above 32 km displays a clear recovery. Nevertheless, a clear detection of TCO recovery in observations remains elusive, and there is mounting evidence of decreasing ozone in the lower stratosphere (below 24 km) in the tropics out to the mid-latitudes (30-60°). Chemistry climate models (CCMs) predict that lower stratospheric ozone will decrease in the tropics by 2100, but not at mid-latitudes.<br> <br>Here, we compare the CCMVal-2 models, which informed the WMO 2014 ozone assessment and show similar tendencies to more recent CCMI data, with observations over 1998-2016. We find that over this period, modelled ozone declines in the tropics are similar to those seen in observations and are likely driven by increased tropical upwelling. Conversely, CCMs generally show ozone increases in the mid-latitude lower stratosphere where observations show a negative tendency. We provide evidence from JRA-55 and ERA-Interim reanalyses indicating that mid-latitude trends are due to enhanced mixing between the tropics and extratropics, in agreement with other studies. </p><p>Additional analysis of temperature and water vapour further supports our findings. Overall, our results suggest that expected changes in large scale circulation from increasing greenhouse gases may now already be underway. While model projections suggest extra-tropical ozone should recover by 2100, our study raises questions about their ability to simulate lower stratospheric changes in this region.</p>

scholarly journals Stratospheric ozone in the post-CFC era

2008 ◽  
Vol 8 (6) ◽  
pp. 20223-20237 ◽  
Author(s):  
F. Li ◽  
R. S. Stolarski ◽  
P. A. Newman
Keyword(s):  
Greenhouse Gas ◽  
21St Century ◽  
Crucial Role ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Advective Transport ◽  
Recent Past ◽  
Column Ozone ◽  
The Tropics

Abstract. Vertical and latitudinal changes in the stratospheric ozone in the post-chlorofluorocarbon (CFC) era are investigated using simulations of the recent past and the 21st century with a coupled chemistry-climate model. Model results reveal that, in the 2060s when the stratospheric halogen loading is projected to return to its 1980 values, the extratropical column ozone is significantly higher than that in 1975–1984, but the tropical column ozone does not recover to 1980 values. Upper and lower stratospheric ozone changes in the post-CFC era have very different patterns. Above 15 hPa ozone increases almost latitudinally uniformly by 6 Dobson Unit (DU), whereas below 15 hPa ozone decreases in the tropics by 8 DU and increases in the extratropics by up to 16 DU. The upper stratospheric ozone increase is a photochemical response to greenhouse gas induced strong cooling, and the lower stratospheric ozone changes are consistent with enhanced mean advective transport due to a stronger Brewer-Dobson circulation. The model results suggest that the strengthening of the Brewer-Dobson circulation plays a crucial role in ozone recovery and ozone distributions in the post-CFC era.

scholarly journals Improving Antarctic Total Ozone Projections by a Process-Oriented Multiple Diagnostic Ensemble Regression

2013 ◽  
Vol 70 (12) ◽  
pp. 3959-3976 ◽  
Author(s):  
Alexey Yu. Karpechko ◽  
Douglas Maraun ◽  
Veronika Eyring
Keyword(s):  
Regression Model ◽  
Total Ozone ◽  
Climate Models ◽  
Prediction Interval ◽  
Stratospheric Ozone ◽  
Total Column Ozone ◽  
Process Oriented ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Ensemble Regression

Abstract Accurate projections of stratospheric ozone are required because ozone changes affect exposure to ultraviolet radiation and tropospheric climate. Unweighted multimodel ensemble-mean (uMMM) projections from chemistry–climate models (CCMs) are commonly used to project ozone in the twenty-first century, when ozone-depleting substances are expected to decline and greenhouse gases are expected to rise. Here, the authors address the question of whether Antarctic total column ozone projections in October given by the uMMM of CCM simulations can be improved by using a process-oriented multiple diagnostic ensemble regression (MDER) method. This method is based on the correlation between simulated future ozone and selected key processes relevant for stratospheric ozone under present-day conditions. The regression model is built using an algorithm that selects those process-oriented diagnostics that explain a significant fraction of the spread in the projected ozone among the CCMs. The regression model with observed diagnostics is then used to predict future ozone and associated uncertainty. The precision of the authors’ method is tested in a pseudoreality; that is, the prediction is validated against an independent CCM projection used to replace unavailable future observations. The tests show that MDER has higher precision than uMMM, suggesting an improvement in the estimate of future Antarctic ozone. The authors’ method projects that Antarctic total ozone will return to 1980 values at around 2055 with the 95% prediction interval ranging from 2035 to 2080. This reduces the range of return dates across the ensemble of CCMs by about a decade and suggests that the earliest simulated return dates are unlikely.

scholarly journals Multi-model assessment of stratospheric ozone return dates and ozone recovery in CCMVal-2 models

2010 ◽  
Vol 10 (19) ◽  
pp. 9451-9472 ◽  
Author(s):  
V. Eyring ◽  
I. Cionni ◽  
G. E. Bodeker ◽  
A. J. Charlton-Perez ◽  
D. E. Kinnison ◽  
...  
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Full Recovery ◽  
Steady Increase ◽  
Model Assessment ◽  
Total Column Ozone ◽  
Column Ozone ◽  
Total Column

Abstract. Projections of stratospheric ozone from a suite of chemistry-climate models (CCMs) have been analyzed. In addition to a reference simulation where anthropogenic halogenated ozone depleting substances (ODSs) and greenhouse gases (GHGs) vary with time, sensitivity simulations with either ODS or GHG concentrations fixed at 1960 levels were performed to disaggregate the drivers of projected ozone changes. These simulations were also used to assess the two distinct milestones of ozone returning to historical values (ozone return dates) and ozone no longer being influenced by ODSs (full ozone recovery). The date of ozone returning to historical values does not indicate complete recovery from ODSs in most cases, because GHG-induced changes accelerate or decelerate ozone changes in many regions. In the upper stratosphere where CO2-induced stratospheric cooling increases ozone, full ozone recovery is projected to not likely have occurred by 2100 even though ozone returns to its 1980 or even 1960 levels well before (~2025 and 2040, respectively). In contrast, in the tropical lower stratosphere ozone decreases continuously from 1960 to 2100 due to projected increases in tropical upwelling, while by around 2040 it is already very likely that full recovery from the effects of ODSs has occurred, although ODS concentrations are still elevated by this date. In the midlatitude lower stratosphere the evolution differs from that in the tropics, and rather than a steady decrease in ozone, first a decrease in ozone is simulated from 1960 to 2000, which is then followed by a steady increase through the 21st century. Ozone in the midlatitude lower stratosphere returns to 1980 levels by ~2045 in the Northern Hemisphere (NH) and by ~2055 in the Southern Hemisphere (SH), and full ozone recovery is likely reached by 2100 in both hemispheres. Overall, in all regions except the tropical lower stratosphere, full ozone recovery from ODSs occurs significantly later than the return of total column ozone to its 1980 level. The latest return of total column ozone is projected to occur over Antarctica (~2045–2060) whereas it is not likely that full ozone recovery is reached by the end of the 21st century in this region. Arctic total column ozone is projected to return to 1980 levels well before polar stratospheric halogen loading does so (~2025–2030 for total column ozone, cf. 2050–2070 for Cly+60×Bry) and it is likely that full recovery of total column ozone from the effects of ODSs has occurred by ~2035. In contrast to the Antarctic, by 2100 Arctic total column ozone is projected to be above 1960 levels, but not in the fixed GHG simulation, indicating that climate change plays a significant role.

scholarly journals Inconsistencies between chemistry climate model and observed lower stratospheric trends since 1998

2019 ◽  
Author(s):  
William T. Ball ◽  
Gabriel Chiodo ◽  
Marta Abalos ◽  
Justin Alsing
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Ozone Layer ◽  
Montreal Protocol ◽  
Total Column Ozone ◽  
Temperature Trends ◽  
Ozone Depleting Substances ◽  
The Tropics

Abstract. The stratospheric ozone layer shields surface life from harmful ultraviolet radiation. Following the Montreal Protocol ban of long-lived ozone depleting substances (ODSs), rapid depletion of total column ozone (TCO) ceased in the late 1990s and ozone above 32 km now enjoys a clear recovery. However, there is still no confirmation of TCO recovery, and evidence has emerged that ongoing quasi-global (60° S–60° N) lower stratospheric ozone decreases may be responsible, dominated by low latitudes (30° S–30° N). Chemistry climate models (CCMs) used to project future changes predict that lower stratospheric ozone will decrease in the tropics by 2100, but not at mid-latitudes (30°–60°). Here, we show that CCMs display an ozone decline similar to that observed in the tropics over 1998–2016, likely driven by a increase of tropical upwelling. On the other hand, mid-latitude lower stratospheric ozone is observed to decrease, while CCMs show an increase. Despite opposing lower stratospheric ozone changes, which should induce opposite temperature trends, CCM and observed temperature trends agree; we demonstrate that opposing model-observation stratospheric water vapour (SWV) trends, and their associated radiative effects, explain why temperature changes agree in spite of opposing ozone trends. We provide new evidence that the observed mid-latitude trends can be explained by enhanced mixing between the tropics and extratropics. We further show that the temperature trends are consistent with the observed mid-latitude ozone decrease. Together, our results suggest that large scale circulation changes expected in the future from increased greenhouse gases (GHGs) may now already be underway, but that most CCMs are not simulating well mid-latitude ozone layer changes. The reason CCMs do not exhibit the observed changes urgently needs to be understood to improve confidence in future projections of the ozone layer.

scholarly journals Attribution of observed changes in stratospheric ozone and temperature

2010 ◽  
Vol 10 (7) ◽  
pp. 17341-17367
Author(s):  
N. P. Gillett ◽  
H. Akiyoshi ◽  
S. Bekki ◽  
V. Eyring ◽  
R. Garcia ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Total Ozone ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Total Column Ozone ◽  
Detection And Attribution ◽  
Stratospheric Temperature ◽  
Ozone Depleting Substances ◽  
Column Ozone ◽  
Total Column

Abstract. Three recently-completed sets of simulations of multiple chemistry-climate models with greenhouse gases only, with all anthropogenic forcings, and with anthropogenic and natural forcings, allow the causes of observed stratospheric changes to be quantitatively assessed using detection and attribution techniques. The total column ozone response to halogenated ozone depleting substances and to natural forcings is detectable and consistent in models and observations. However, the total ozone response to greenhouse gases in the models and observations appears to be inconsistent, which may be due to the models' inability to properly simulate tropospheric ozone changes. In the middle and upper stratosphere, simulated and observed SBUV/SAGE ozone changes are broadly consistent, and separate anthropogenic and natural responses are detectable in observations. The influence of ozone depleting substances and natural forcings can also be detected separately in observed lower stratospheric temperature, and the magnitudes of the simulated and observed responses to these forcings and to greenhouse gas changes are found to be consistent. In the mid and upper stratosphere the simulated natural and combined anthropogenic responses are detectable and consistent with observations, but the influences of greenhouse gases and ozone-depleting substances could not be separately detected in our analysis.

scholarly journals Multi-model assessment of stratospheric ozone return dates and ozone recovery in CCMVal-2 models

2010 ◽  
Vol 10 (5) ◽  
pp. 11659-11710 ◽  
Author(s):  
V. Eyring ◽  
I. Cionni ◽  
G. E. Bodeker ◽  
A. J. Charlton-Perez ◽  
D. E. Kinnison ◽  
...  
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Full Recovery ◽  
Steady Increase ◽  
Model Assessment ◽  
Total Column Ozone ◽  
Column Ozone ◽  
Total Column

Abstract. Projections of stratospheric ozone from a suite of chemistry-climate models (CCMs) have been analyzed. In addition to a reference simulation where anthropogenic halogenated ozone depleting substances (ODSs) and greenhouse gases (GHGs) vary with time, sensitivity simulations with either ODSs or GHGs concentrations fixed at 1960 levels were performed to disaggregate the drivers of projected ozone changes. These simulations were also used to assess the two distinct milestones of ozone returning to historical values (ozone return dates) and ozone no longer being influenced by ODSs (full ozone recovery). These two milestones are different. The date of ozone returning to historical values does not indicate complete recovery from ODSs in most cases, because GHG induced changes accelerate or decelerate ozone changes in many regions. In the upper stratosphere where GHG induced stratospheric cooling increases ozone, full ozone recovery has not likely occurred by 2100 while ozone returns to its 1980 or even 1960 levels well before (~2025 and 2040, respectively). In contrast, in the tropical lower stratosphere ozone decreases continuously from 1960 to 2100 due to projected increases in tropical upwelling, while by around 2040 it is already very likely that full recovery from the effects of ODSs has occurred, although ODS concentrations are still elevated by this date. In the lower midlatitude stratosphere the evolution differs from that in the tropics, and rather than a steady decrease of ozone, first a decrease of ozone is simulated between 1960 and 2000, which is then followed by a steady increase throughout the 21st century. Ozone in the lower stratosphere midlatitudes returns to its 1980 levels ${\\sim}$2045 in the NH and ~2055 in the SH, and full ozone recovery is likely reached by 2100 in both hemispheres. Overall, in all regions except the tropical lower stratosphere, full ozone recovery from ODSs occurs significantly later than the return of total column ozone to its 1980 level. The latest return of total column ozone is projected to occur over Antarctica (~2050–2060) whereas it is not likely that full ozone recovery is reached by the end of the 21st century in this region. Arctic total column ozone is projected to return to 1980 levels well before Cly does so (~2020–2030) and while it is likely that full recovery of ozone from the effects of ODSs has occurred by ~2035, at no time before 2100 is it very likely that full recovery has occurred. In contrast to the Antarctic, by 2100 Arctic total column ozone is projected to be above 1960 levels, but not in the fixed GHG simulation, indicating that climate change plays a significant role.

scholarly journals Stratospheric ozone in the post-CFC era

2009 ◽  
Vol 9 (6) ◽  
pp. 2207-2213 ◽  
Author(s):  
F. Li ◽  
R. S. Stolarski ◽  
P. A. Newman
Keyword(s):  
Greenhouse Gas ◽  
21St Century ◽  
Crucial Role ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Advective Transport ◽  
Recent Past ◽  
Column Ozone ◽  
The Tropics

Abstract. Vertical and latitudinal changes in the stratospheric ozone in the post-chlorofluorocarbon (CFC) era are investigated using simulations of the recent past and the 21st century with a coupled chemistry-climate model. Model results reveal that, in the 2060s when the stratospheric halogen loading is projected to return to its 1980 values, the extratropical column ozone is significantly higher than that in 1975–1984, but the tropical column ozone does not recover to 1980 values. Upper and lower stratospheric ozone changes in the post-CFC era have very different patterns. Above 15 hPa ozone increases almost latitudinally uniformly by 6 Dobson Unit (DU), whereas below 15 hPa ozone decreases in the tropics by 8 DU and increases in the extratropics by up to 16 DU. The upper stratospheric ozone increase is a photochemical response to greenhouse gas induced strong cooling, and the lower stratospheric ozone changes are consistent with enhanced mean advective transport due to a stronger Brewer-Dobson circulation. The model results suggest that the strengthening of the Brewer-Dobson circulation plays a crucial role in ozone recovery and ozone distributions in the post-CFC era.

scholarly journals Stratospheric ozone measurements at Arosa (Switzerland): History and scientific relevance

2017 ◽  
Author(s):  
Johannes Staehelin ◽  
Pierre Viatte ◽  
Rene Stübi ◽  
Fiona Tummon ◽  
Thomas Peter
Keyword(s):  
Ozone Depletion ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Cost Savings ◽  
Ozone Layer ◽  
Montreal Protocol ◽  
Global Environmental Policy ◽  
History Of ◽  
Ozone Depleting Substances ◽  
Column Ozone

Abstract. In 1926 the stratospheric ozone measurements of the Light Climatic Observatory (LKO) of Arosa (Switzerland) started, marking the start of the world's longest total (or column) ozone measurements. These measurements were driven by the recognition of the importance of atmospheric ozone for human health as well as by scientific curiosity in this by then not well characterized atmospheric trace gas. Since the mid-1970s ground-based measurements of stratospheric ozone have also been justified to society by the need to document the effects of anthropogenic Ozone Depleting Substances (ODSs), which cause stratospheric ozone depletion. Levels of ODSs peaked around the mid-1990s as a result of a global environmental policy to protect the ozone layer implemented by the 1987 Montreal Protocol and its subsequent amendments and adjustments. Consequently, chemical ozone depletion caused by ODSs stopped worsening around the mid-1990s. This renders justification for continued ozone measurements more difficult, and is likely to do so even more in future, when stratospheric ozone recovery is expected. Tendencies of increased cost savings in ozone measurements seem perceptible worldwide, also in Arosa. However, the large natural variability in ozone on diurnal, seasonal and interannual scales complicates to demonstrate the success of the Montreal Protocol. Moreover, chemistry-climate models predict a “super-recovery” of the ozone layer in the second half of this century, i.e. an increase of ozone concentrations beyond pre-1970 levels, as a consequence of ongoing climate change. This paper presents the evolution of the ozone layer and the history of international ozone research and discusses the justification of these measurements for past, present and future.

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