scholarly journals Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011)

2012 ◽  
Vol 12 (5) ◽  
pp. 2533-2540 ◽  
Author(s):  
C. McLandress ◽  
J. Perlwitz ◽  
T. G. Shepherd
Keyword(s):  
Northern Hemisphere ◽  
Climate Models ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Temperature Response ◽  
Ocean Model ◽  
Tropospheric Temperature ◽  
Cmip3 Model ◽  
Incomplete Removal

Abstract. In a recent paper Hu et al. (2011) suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of CMIP3 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We suggest that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.

scholarly journals Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011)

2011 ◽  
Vol 11 (12) ◽  
pp. 32993-33012 ◽  
Author(s):  
C. McLandress ◽  
J. Perlwitz ◽  
T. G. Shepherd
Keyword(s):  
Northern Hemisphere ◽  
Climate Models ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Temperature Response ◽  
Ocean Model ◽  
Tropospheric Temperature ◽  
Surface Warming ◽  
Incomplete Removal

Abstract. In a recent paper Hu et al. (2011) suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of IPCC AR4 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We argue that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.

scholarly journals The representation of solar cycle signals in stratospheric ozone. Part II: Analysis of global models

2017 ◽  
Author(s):  
Amanda C. Maycock ◽  
Katja Matthes ◽  
Susann Tegtmeier ◽  
Hauke Schmidt ◽  
Rémi Thiéblemont ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Climate Models ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Temperature Response ◽  
Solar Variability ◽  
High Latitudes ◽  
Stratospheric Temperature ◽  
The Impact

Abstract. The impact of changes in incoming solar irradiance on stratospheric ozone abundances should be included in climate model simulations to fully capture the atmospheric response to solar variability. This study presents the first systematic comparison of the solar-ozone response (SOR) during the 11 year solar cycle amongst different chemistry-climate models (CCMs) and ozone databases specified in climate models that do not include chemistry. We analyse the SOR in eight CCMs from the WCRP/SPARC Chemistry-Climate Model Initiative (CCMI-1) and compare these with three ozone databases: the Bodeker Scientific database, the SPARC/AC&C database for CMIP5, and the SPARC/CCMI database for CMIP6. The results reveal substantial differences in the representation of the SOR between the CMIP5 and CMIP6 ozone databases. The peak amplitude of theSOR in the upper stratosphere (1–5 hPa) decreases from 5 % to 2 % between the CMIP5 and CMIP6 databases. This difference is because the CMIP5 database was constructed from a regression model fit to satellite observations, whereas the CMIP6 database is constructed from CCM simulations, which use a spectral solar irradiance (SSI) dataset with relatively weak UV forcing. The SOR in the CMIP6 ozone database is therefore implicitly more similar to the SOR in the CCMI-1 models than to the CMIP5 ozone database, which shows a greater resemblance in amplitude and structure to the SOR in the Bodeker database. The latitudinal structure of the annual mean SOR in the CMIP6 ozone database and CCMI-1 models is considerably smoother than in the CMIP5 database, which shows strong gradients in the SOR across the midlatitudes owing to the paucity of observations at high latitudes. The SORs in the CMIP6 ozone database and in the CCMI-1 models show a strong seasonal dependence, including large meridional gradients at mid to high latitudes during winter; such seasonal variations in the SOR are not included in the CMIP5 ozone database. Sensitivity experiments with a global atmospheric model without chemistry (ECHAM6.3) are performed to assess the impact of changes in the representation of the SOR and SSI forcing between CMIP5 and CMIP6. The experiments show that the smaller amplitude of the SOR in the CMIP6 ozone database compared to CMIP5 causes a decrease in the modelled tropical stratospheric temperature response over the solar cycle of up to 0.6 K, or around 50 % of the total amplitude. The changes in the SOR explain most of the difference in the amplitude of the tropical stratospheric temperature response in the case with combined changes in SOR and SSI between CMIP5 and CMIP6. The results emphasise the importance of adequately representing the SOR in climate models to capture the impact of solar variability on the atmosphere. Since a number of limitations in the representation of the SOR in the CMIP5 ozone database have been identified, CMIP6 models without chemistry are encouraged to use the CMIP6 ozone database to capture the climate impacts of solar variability.

scholarly journals Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011)

2012 ◽  
Vol 12 (1) ◽  
pp. 2853-2861 ◽  
Author(s):  
M. Previdi ◽  
L. M. Polvani
Keyword(s):  
Greenhouse Gases ◽  
Surface Temperature ◽  
Temperature Change ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Temperature Response ◽  
First Century ◽  
Tropospheric Temperature ◽  
Surface Temperature Change ◽  
Twenty First Century

Abstract. Stratospheric ozone recovery is expected to figure prominently in twenty-first century climate change. In a recent paper, Hu et al. (2011) argue that one impact of ozone recovery will be to enhance the warming of the surface-troposphere system produced by increases in well-mixed greenhouse gases; furthermore, this enhanced warming would be strongest in the Northern Hemisphere, which is surprising since previous studies have consistently shown the effects of stratospheric ozone changes to be most pronounced in the Southern Hemisphere. Hu et al. (2011) base their claims largely on differences in the simulated temperature change between two groups of IPCC climate models, one group which included stratospheric ozone recovery in its twenty-first century simulations and a second group which did not. Both groups of models were forced with the same increases in well-mixed greenhouse gases according to the A1B emissions scenario. In the current work, we compare the surface temperature responses of the same two groups of models in a different experiment in which atmospheric CO2 was increased by 1% per year until doubling. We find remarkably similar differences in the simulated surface temperature change between the two sets of models as Hu et al. (2011) found for the A1B experiment, suggesting that the enhanced warming which they attribute to stratospheric ozone recovery is actually a reflection of different responses of the two model groups to greenhouse gas forcing.

scholarly journals Formulation of an ocean model for global climate simulations

2005 ◽  
Vol 2 (3) ◽  
pp. 165-246 ◽  
Author(s):  
S. M. Griffies ◽  
A. Gnanadesikan ◽  
K. W. Dixon ◽  
J. P. Dunne ◽  
R. Gerdes ◽  
...  
Keyword(s):  
Free Surface ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Three Dimensional ◽  
Coupled Model ◽  
Ocean Model ◽  
Tidal Mixing ◽  
The Arctic ◽  
Tracer Transport

Abstract. This paper summarizes the formulation of the ocean component to the Geophysical Fluid Dynamics Laboratory's (GFDL) coupled climate model used for the 4th IPCC Assessment (AR4) of global climate change. In particular, it reviews elements of ocean climate models and how they are pieced together for use in a state-of-the-art coupled model. Novel issues are also highlighted, with particular attention given to sensitivity of the coupled simulation to physical parameterizations and numerical methods. Features of the model described here include the following: (1) tripolar grid to resolve the Arctic Ocean without polar filtering, (2) partial bottom step representation of topography to better represent topographically influenced advective and wave processes, (3) more accurate equation of state, (4) three-dimensional flux limited tracer advection to reduce overshoots and undershoots, (5) incorporation of regional climatological variability in shortwave penetration, (6) neutral physics parameterization for representation of the pathways of tracer transport, (7) staggered time stepping for tracer conservation and numerical efficiency, (8) anisotropic horizontal viscosities for representation of equatorial currents, (9) parameterization of exchange with marginal seas, (10) incorporation of a free surface that accomodates a dynamic ice model and wave propagation, (11) transport of water across the ocean free surface to eliminate unphysical "virtual tracer flux" methods, (12) parameterization of tidal mixing on continental shelves.

scholarly journals Contributions to stratospheric ozone changes from ozone depleting substances and greenhouse gases

2010 ◽  
Vol 10 (4) ◽  
pp. 9647-9694 ◽  
Author(s):  
D. A. Plummer ◽  
J. F. Scinocca ◽  
T. G. Shepherd ◽  
M. C. Reader ◽  
A. I. Jonsson
Keyword(s):  
Greenhouse Gases ◽  
21St Century ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Ocean Model ◽  
Residual Circulation ◽  
Chemical Effects ◽  
Ozone Depleting Substances ◽  
Year 2000

Abstract. A state-of-the-art chemistry climate model coupled to a three-dimensional ocean model is used to produce three experiments, all seamlessly covering the period 1950–2100, forced by different combinations of long-lived Greenhouse Gases (GHGs) and Ozone Depleting Substances (ODSs). The experiments are designed to investigate the mechanisms by which GHGs and ODSs affect the evolution of ozone, including changes in the Brewer-Dobson circulation of the stratosphere and cooling of the upper stratosphere by CO2. Separating the effects of GHGs and ODSs on ozone, we find the decrease in upper stratospheric ozone from ODSs up to the year 2000 is approximately 30% larger than the actual decrease in ozone due to the offsetting effects of cooling by increased CO2. Over the 21st century, as ODSs decrease, continued cooling from CO2 is projected to account for more than 50% of the projected increase in upper stratospheric ozone. Changes below 20 hPa show a redistribution of ozone from tropical to extra-tropical latitudes with an increase in the Brewer-Dobson circulation, while globally averaged the amount of ozone below 20 hPa decreases over the 21st century. Further analysis by linear regression shows that changes associated with GHGs do not appreciably alter the recovery of stratospheric ozone from the effects of ODSs; over much of the stratosphere ozone recovery follows the decline of halogen concentrations within statistical uncertainty, though the lower polar stratosphere of the Southern Hemisphere is an exception with ozone concentrations recovering more slowly than indicated by the halogen concentrations. These results also reveal the degree to which climate change, and stratospheric CO2 cooling in particular, mutes the chemical effects of N2O on ozone in the standard future scenario used for the WMO Ozone Assessment. Increases in the residual circulation of the atmosphere and chemical effects from CO2 cooling more than halve the increase in reactive nitrogen in the mid to upper stratosphere that results from the specified increase in N2O between 1950 and 2100.

scholarly journals Tropospheric temperature response to stratospheric ozone recovery in the 21st century

2011 ◽  
Vol 11 (15) ◽  
pp. 7687-7699 ◽  
Author(s):  
Y. Hu ◽  
Y. Xia ◽  
Q. Fu
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Temperature Response ◽  
Ozone Layer ◽  
Montreal Protocol ◽  
Polar Regions ◽  
Tropospheric Temperature ◽  
Intergovernmental Panel ◽  
Maximum Enhancement

Abstract. Recent simulations predicted that the stratospheric ozone layer will likely return to pre-1980 levels in the middle of the 21st century, as a result of the decline of ozone depleting substances under the Montreal Protocol. Since the ozone layer is an important component in determining stratospheric and tropospheric-surface energy balance, the recovery of stratospheric ozone may have significant impact on tropospheric-surface climate. Here, using multi-model results from both the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4) models and coupled chemistry-climate models, we show that as ozone recovery is considered, the troposphere is warmed more than that without considering ozone recovery, suggesting an enhancement of tropospheric warming due to ozone recovery. It is found that the enhanced tropospheric warming is mostly significant in the upper troposphere, with a global and annual mean magnitude of ~0.41 K for 2001–2050. We also find that relatively large enhanced warming occurs in the extratropics and polar regions in summer and autumn in both hemispheres, while the enhanced warming is stronger in the Northern Hemisphere than in the Southern Hemisphere. Enhanced warming is also found at the surface. The global and annual mean enhancement of surface warming is about 0.16 K for 2001–2050, with maximum enhancement in the winter Arctic.

scholarly journals Preindustrial to present day changes in tropospheric hydroxyl radical and methane lifetime from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

2012 ◽  
Vol 12 (11) ◽  
pp. 30755-30804 ◽  
Author(s):  
V. Naik ◽  
A. Voulgarakis ◽  
A. M. Fiore ◽  
L. W. Horowitz ◽  
J.-F. Lamarque ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Hydroxyl Radical ◽  
Northern Hemisphere ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Tropospheric Temperature ◽  
Model Intercomparison ◽  
Intercomparison Project ◽  
Global Mean

Abstract. We have analysed results from 17 global models, participating in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), to explore trends in hydroxyl radical concentration (OH) and methane (CH4) lifetime since preindustrial times (1850) and gain a better understanding of their key drivers. For the present day (2000), the models tend to simulate higher OH abundances in the Northern Hemisphere versus Southern Hemisphere. Evaluation of simulated carbon monoxide concentrations, the primary sink for OH, against observations suggests low biases in the Northern Hemisphere that may contribute to the high north-south OH asymmetry in the models. A comparison of modelled and observed methyl chloroform lifetime suggests that the present day global multi-model mean OH concentration is slightly overestimated. Despite large regional changes, the modelled global mean OH concentration is roughly constant over the past 150 yr, due to concurrent increases in OH sources (humidity, tropospheric ozone, and NOx emissions), together with decreases in stratospheric ozone and increase in tropospheric temperature, compensated by increases in OH sinks (methane abundance, carbon monoxide and non-methane volatile organic carbon (NMVOC) emissions). The large intermodel diversity in the sign and magnitude of OH and methane lifetime changes over this period reflects differences in the relative importance of chemical and physical drivers of OH within each model. For the 1980 to 2000 period, we find that climate warming and a slight increase in mean OH leads to a 4.3 ± 1.9% decrease in the methane lifetime. Analysing sensitivity simulations performed by 10 models, we find that preindustrial to present day climate change decreased the methane lifetime by about 4 months, representing a negative feedback on the climate system. Further, using a subset of the models, we find that global mean OH increased by 46.4 ± 12.2% in response to preindustrial to present day anthropogenic NOx emission increases, and decreased by 17.3 ± 2.3%, 7.6 ± 1.5%, and 3.1 ± 3.0% due to methane burden, and anthropogenic CO, and NMVOC emissions increases, respectively.

scholarly journals On the attribution of stratospheric ozone and temperature changes to changes in ozone-depleting substances and well-mixed greenhouse gases

2007 ◽  
Vol 7 (4) ◽  
pp. 12327-12347 ◽  
Author(s):  
T. G. Shepherd ◽  
A. I. Jonsson
Keyword(s):  
Climate Model ◽  
Traditional Approach ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Temperature Response ◽  
Temperature Changes ◽  
Stratospheric Temperature ◽  
Cooling Effects ◽  
Ozone Depleting Substances ◽  
Global Mean

Abstract. The vertical profile of global-mean stratospheric temperature changes has traditionally represented an important diagnostic for the attribution of the cooling effects of stratospheric ozone depletion and CO2 increases. However, CO2-induced cooling alters ozone abundance by perturbing ozone chemistry, thereby coupling the stratospheric ozone-temperature response to changes in CO2 and ozone-depleting substances (ODSs). Here we untangle the ozone-temperature coupling and show that the attribution of global-mean stratospheric temperature changes to CO2 and ODS changes (which are the true anthropogenic forcing agents) can be quite different from the traditional attribution to CO2 and ozone changes. The significance of these effects is quantified empirically using simulations from a three-dimensional chemistry-climate model. The results confirm the essential validity of the traditional approach in attributing changes during the past period of rapid ODS increases, although we find that about 10% of the upper stratospheric ozone decrease from ODS increases over the period 1975–1995 was offset by the increase in CO2, and the CO2-induced cooling in the upper stratosphere has been somewhat overestimated. When considering ozone recovery, however, the ozone-temperature coupling is a first-order effect; fully 2/5 of the upper stratospheric ozone increase projected to occur from 2010–2040 is attributable to CO2 increases. Thus, it has now become necessary to base attribution of global-mean stratospheric temperature changes on CO2 and ODS changes rather than on CO2 and ozone changes.

scholarly journals Paleoclimate Constraints on the Spatiotemporal Character of Past and Future Droughts

2020 ◽  
Vol 33 (22) ◽  
pp. 9883-9903
Author(s):  
S. Coats ◽  
J. E. Smerdon ◽  
S. Stevenson ◽  
J. T. Fasullo ◽  
B. Otto-Bliesner ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Climate Models ◽  
Climate Model ◽  
Dimensional Space ◽  
Three Dimensional ◽  
First Century ◽  
Spatiotemporal Characteristics ◽  
Dimensional Space Time ◽  
Simulated Drought ◽  
Climate Model Simulations

AbstractMachine-learning-based methods that identify drought in three-dimensional space–time are applied to climate model simulations and tree-ring-based reconstructions of hydroclimate over the Northern Hemisphere extratropics for the past 1000 years, as well as twenty-first-century projections. Analyzing reconstructed and simulated drought in this context provides a paleoclimate constraint on the spatiotemporal characteristics of simulated droughts. Climate models project that there will be large increases in the persistence and severity of droughts over the coming century, but with little change in their spatial extent. Nevertheless, climate models exhibit biases in the spatiotemporal characteristics of persistent and severe droughts over parts of the Northern Hemisphere. We use the paleoclimate record and results from a linear inverse modeling-based framework to conclude that climate models underestimate the range of potential future hydroclimate states. Complicating this picture, however, are divergent changes in the characteristics of persistent and severe droughts when quantified using different hydroclimate metrics. Collectively our results imply that these divergent responses and the aforementioned biases must be better understood if we are to increase confidence in future hydroclimate projections. Importantly, the novel framework presented herein can be applied to other climate features to robustly describe their spatiotemporal characteristics and provide constraints on future changes to those characteristics.

scholarly journals Quantifying the contributions to stratospheric ozone changes from ozone depleting substances and greenhouse gases

2010 ◽  
Vol 10 (18) ◽  
pp. 8803-8820 ◽  
Author(s):  
D. A. Plummer ◽  
J. F. Scinocca ◽  
T. G. Shepherd ◽  
M. C. Reader ◽  
A. I. Jonsson
Keyword(s):  
Greenhouse Gases ◽  
21St Century ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Ocean Model ◽  
Residual Circulation ◽  
Total Column Ozone ◽  
Chemical Effects ◽  
Ozone Depleting Substances

Abstract. A state-of-the-art chemistry climate model coupled to a three-dimensional ocean model is used to produce three experiments, all seamlessly covering the period 1950–2100, forced by different combinations of long-lived Greenhouse Gases (GHGs) and Ozone Depleting Substances (ODSs). The experiments are designed to quantify the separate effects of GHGs and ODSs on the evolution of ozone, as well as the extent to which these effects are independent of each other, by alternately holding one set of these two forcings constant in combination with a third experiment where both ODSs and GHGs vary. We estimate that up to the year 2000 the net decrease in the column amount of ozone above 20 hPa is approximately 75% of the decrease that can be attributed to ODSs due to the offsetting effects of cooling by increased CO2. Over the 21st century, as ODSs decrease, continued cooling from CO2 is projected to account for more than 50% of the projected increase in ozone above 20 hPa. Changes in ozone below 20 hPa show a redistribution of ozone from tropical to extra-tropical latitudes with an increase in the Brewer-Dobson circulation. In addition to a latitudinal redistribution of ozone, we find that the globally averaged column amount of ozone below 20 hPa decreases over the 21st century, which significantly mitigates the effect of upper stratospheric cooling on total column ozone. Analysis by linear regression shows that the recovery of ozone from the effects of ODSs generally follows the decline in reactive chlorine and bromine levels, with the exception of the lower polar stratosphere where recovery of ozone in the second half of the 21st century is slower than would be indicated by the decline in reactive chlorine and bromine concentrations. These results also reveal the degree to which GHG-related effects mute the chemical effects of N2O on ozone in the standard future scenario used for the WMO Ozone Assessment. Increases in the residual circulation of the atmosphere and chemical effects from CO2 cooling more than halve the increase in reactive nitrogen in the mid to upper stratosphere that results from the specified increase in N2O between 1950 and 2100.

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