New Directions: Stratospheric ozone recovery in a changing atmosphere (original) (raw)
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Reconciliation of halogen-induced ozone loss with the total-column ozone record
Nature Geoscience, 2014
The observed depletion of the ozone layer is attributed to anthropogenic 1 halogens, but the precision of this attribution is complicated by natural 2 dynamical variability (year-to-year meteorological variations) and by changes 3 in tropospheric ozone, leaving key aspects of the observed total ozone record 4 unexplained. These include inter-hemispheric differences in the response to 5 the Mount Pinatubo volcanic eruption, the lack of a decline prior to 1980 and 6 of any long-term decline in the tropics, and the apparent delay in ozone 7 recovery despite the significant decline of stratospheric halogen loading since 8 the late 1990s. Here we use a chemistry-climate model constrained by 9 observed meteorology to remove the effects of dynamical variability and to 10 estimate changes in tropospheric ozone. Ozone loss is shown to closely follow 11 stratospheric halogen loading, with pronounced enhancements in both 12 hemispheres following the volcanic eruptions of El Chichon and, especially, 13 Mount Pinatubo. Approximately 40% of the long-term non-volcanic loss is 14 found to have occurred by 1980. Long-term ozone loss is found in the tropical 15 stratosphere, but is masked in the column by tropospheric increases. Ozone 16 loss has declined by over 10% since stratospheric halogen loading peaked in 17 the late 1990s, indicating that recovery of the ozone layer is well underway. 18 19 Anthropogenic emissions of halogenated (principally chlorine) species have led to 20 an observable depletion of the ozone layer 1. Ozone depletion has been a matter of 21 wide public concern because of its implications for human and ecosystem health 2. 22 As a result of comprehensive controls on ozone-depleting substances, stratospheric
Stratospheric Ozone and Surface Ultraviolet Radiation
2011
Global Ozone Observations and Interpretation As a result of the Montreal Protocol, ozone is expected to recover from the effect of ozone-depleting substances (ODSs) as their abundances decline in the coming decades. The 2006 Assessment showed that globally averaged column ozone ceased to decline around 1996, meeting the criterion for the first stage of recovery. Ozone is expected to increase as a result of continued decrease in ODSs (second stage of recovery). This chapter discusses recent observations of ozone and ultraviolet radiation in the context of their historical records. Natural variability, observational uncertainty, and stratospheric cooling necessitate a long record in order to attribute an ozone increase to decreases in ODSs. Table S2-1 summarizes ozone changes since 1980. The primary tools used in this Assessment for prediction of ozone are chemistry-climate models (CCMs). These CCMs are designed to represent the processes determining the amount of stratospheric ozone and its response to changes in ODSs and greenhouse gases. Eighteen CCMs have been recently evaluated using a variety of process-based comparisons to measurements. The CCMs are further evaluated here by comparison of trends calculated from measurements with trends calculated from simulations designed to reproduce ozone behavior during an observing period. Total Column Ozone • Average total ozone values in 2006-2009 have remained at the same level for the past decade, about 3.5% and 2.5% below the 1964-1980 averages respectively for 90°S-90°N and 60°S-60°N. Average total ozone from CCM simulations behaves in a manner similar to observations between 1980 and 2009. The average column ozone for 1964-1980 is chosen as a reference for observed changes for two reasons: 1) reliable ground-based observations sufficient to produce a global average are available in this period; 2) a significant trend is not discernible in the observations during this period. • Southern Hemisphere midlatitude (35°S-60°S) annual mean total column ozone amounts over the period 2006-2009 have remained at the same level as observed during 1996-2005, approximately 6% below the 1964-1980 average. Simulations by CCMs also show declines of the same magnitude between 1980 and 1996, and minimal change after 1996, thus both observations and simulations are consistent with the expectations of the impact of ODSs on southern midlatitude ozone. • Northern Hemisphere midlatitude (35°N-60°N) annual mean total column ozone amounts over the period 2006-2009 have remained at the same level as observed during 1998-2005, approximately 3.5% below the 1964-1980 average. A minimum about 5.5% below the 1964-1980 average was reached in the mid-1990s. Simulations by CCMs agree with these measurements, again showing the consistency of data with the expected impact of ODSs. The simulations also indicate that the minimum in the mid-1990s was primarily caused by the ozone response to effects of volcanic aerosols from the 1991 eruption of Mt. Pinatubo. • The latitude dependence of simulated total column ozone trends generally agrees with that derived from measurements, showing large negative trends at Southern Hemisphere mid and high latitudes and Northern Hemisphere midlatitudes for the period of ODS increase. However, in the tropics the statistically significant range of trends produced by CCMs (−1.5 to −4 Dobson units per decade (DU/decade)) does not agree with the trend obtained from measurements (+0.3 ± 1 DU/decade). Ozone Profiles • Northern Hemisphere midlatitude (35°N-60°N) ozone between 12 and 15 km decreased between 1979 and 1995, and increased between 1996 and 2009. The increase since the mid-1990s is larger than the changes expected from the decline in ODS abundances. Increased by 1 to 2%, but uncertainties are large Southern midlatitudes 1980-1996 Declined by 6% No information Declined by about 7% Declined by about 10% Southern midlatitudes 1996-2009 Remained at approximately the same level No statistically significant changes No statistically significant changes Increased by 1 to 3%, but uncertainties are large 2.3 Stratospheric Ozone and Surface UV Polar Ozone Observations and Interpretation • The Antarctic ozone hole continued to appear each spring from 2006 to 2009. This is expected because decreases in stratospheric chlorine and bromine have been moderate over the last few years. Analysis shows that since 1979 the abundance of total column ozone in the Antarctic ozone hole has evolved in a manner consistent with the time evolution of ODSs. Since about 1997 the ODS amounts have been nearly constant and the depth and magnitude of the ozone hole have been controlled by variations in temperature and dynamics. The October mean column ozone within the vortex has been about 40% below 1980 values for the past fifteen years. • Arctic winter and spring ozone loss has varied between 2007 and 2010, but remained in a range comparable to the values that have prevailed since the early 1990s. Chemical loss of about 80% of the losses observed in the record cold winters of 1999/2000 and 2004/2005 has occurred in recent cold winters. • Recent laboratory measurements of the chlorine monoxide dimer (ClOOCl) dissociation cross section and analyses of observations from aircraft and satellites have reaffirmed the fundamental understanding that polar springtime ozone depletion is caused primarily by the ClO + ClO catalytic ozone destruction cycle, with significant contributions from the BrO + ClO cycle. • Polar stratospheric clouds (PSCs) over Antarctica occur more frequently in early June and less frequently in September than expected based on the previous satellite PSC climatology. This result is obtained from measurements by a new class of satellite instruments that provide daily vortex-wide information concerning PSC composition and occurrence in both hemispheres. The previous satellite PSC climatology was developed from solar occultation instruments that have limited daily coverage. • Calculations constrained to match observed temperatures and halogen levels produce Antarctic ozone losses that are close to those derived from data. Without constraints, CCMs simulate many aspects of the Antarctic ozone hole, however they do not simultaneously produce the cold temperatures, isolation from middle latitudes, deep descent, and high amounts of halogens in the polar vortex. Furthermore, most CCMs underestimate the Arctic ozone loss that is derived from observations, primarily because the simulated northern winter vortices are too warm. Ultraviolet Radiation Ground-based measurements of solar ultraviolet (UV) radiation (wavelength 280-400 nanometers) remain limited both spatially and in duration. However, there have been advances both in reconstructing longer-term UV records from other types of ground-based measurements and in satellite UV retrievals. Where these UV data sets coincide, long-term changes agree, even though there may be differences in instantaneous, absolute levels of UV.
Geophysical Research Letters, 1998
Satellite observations of total ozone at 40-60øN are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of ozone depletion. The observations are shown to be consistent with current understanding of the chemistry of ozone depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude ozone depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200-210K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol. SOLOMON ET AL.: MID-LATITUDE OZONE DEPLETION Both the TOMS and SBUV/SBUV2 data show a drop in March following Pinatubo, while little change is evident in October. Both the Earth Probe and NOAA-9 SBUV data
Tropospheric Ozone Assessment Report
Elementa: Science of the Anthropocene, 2020
Our understanding of the processes that control the burden and budget of tropospheric ozone has changed dramatically over the last 60 years. Models are the key tools used to understand these changes, and these underscore that there are many processes important in controlling the tropospheric ozone budget. In this critical review, we assess our evolving understanding of these processes, both physical and chemical. We review model simulations from the International Global Atmospheric Chemistry Atmospheric Chemistry and Climate Model Intercomparison Project and Chemistry Climate Modelling Initiative to assess the changes in the tropospheric ozone burden and its budget from 1850 to 2010. Analysis of these data indicates that there has been significant growth in the ozone burden from 1850 to 2000 (approximately 43 ± 9%) but smaller growth between 1960 and 2000 (approximately 16 ± 10%) and that the models simulate burdens of ozone well within recent satellite estimates. The Chemistry Clim...
Ozone, Climate, and Global Atmospheric Change
Science Activities Classroom Projects and Curriculum Ideas, 1992
was selected as Virginia's Outstanding Scientist for 1987. Also a recipient of the NASA Medal for Exceptions(scientific Achievement, Dr. ~~~i~~ concentrations of the trace gases are measured in terms of wrote the lead article in the Febmfy-March 1981 issue of Science Activities, entitled "The Early Atmosphere: A New Picture." in addition, Dr. Levine edited and contributed to The Photochemistry of Atmospheres: Earth, the Other Planets, and centimeter of air. Trace gases such as ozone (O& carbon Comets, published by Academic Press, Inc., in 1985, and Global-Biomass Burning: Atmospheric, Climatic, and BIospheric dioxide (CO,), methane (CH4), nitrous oxide (N20), chl~rofluorocarbons (CFCs), and halons (brominated CFCs) are measured in parts per million by volume ppmv), parts per billion by volume ppbv), or parts per trillion by volume (pptv). The concentrations of the major and-implIcatIons, published by the MIT Press, Inc., in 1991. http:Nasd-www.larc.nasa.gov/biomassburn/ozone.html 101'2 112004 Ozone, Climate, and Global Atmos Change Table 1-Major and Sdmd 1-Gmes m the Atmoaphere G-Concentration Nitrogen (NJ Oxygen [Od Argon jAr) Water vawr (HLOf 78.08 percent by volume 20.95 percent by vdume 0.93 percent by volume 0 to 1 or 2 percent by wlurne Carbon dioxide (03,) 350 P P W ozone to3 In troposphere In stratosphece 0.02 lo 0.1 ppmu 0.1 rn 10 ppmv Methane [CH,) 1.7 ppmv CFC-12 (CF2ClJ 0.5 ppbv Nitrous oxide {Npf 031 P P CFC-i i [ma,) 0.3 ppbv Habn-1301 (Cf3rF.J 2.0 pptr Halon-121 1 [CBrCIF,) 1.7 pptv Lust Updated: 1 O/OlL?OO2 12:43:45 Web Citrator: P. Kay Costulis (p. k. c o s t i c I i s~l~n r~.. i~~~a~~~~) Responsible NASA Oficial: Dr. Joel S. Levine. Atmospheric Scieiices Conipetericj h ttp://asd-www. larc .nasa.gov/biomass-bundozone. h tml
Geophysical Research Letters, 1992
The eruption of Mt. Pinatubo (15øN, 122øE) on June 15 and 16, 1991, placed a large amount of SO2 and crustal material in the stratosphere. Based on measurements of decreases of stratospheric ozone after previous volcanic eruptions, it was expected that the aerosols deposited into the stratosphere (both directly and as a result of SO2 conversion into particulate sulfate) by this eruption would give rise to significant ozone depletions. To check for such an effect, ozone profiles obtained from ECC sondes before and after the eruption at Brazzaville, Congo (4øS, 15øE), and Ascension Island (8øS, 14øW), are examined. Aerosol profiles determined from a lidar system in the western Pacific (4 ø-6ø1,,1, 125øE) show that most of the material injected into the stratosphere is located between 18 and 28 km with highest mounts at 24-25 km. For the period 3-6 months after the eruption, decreases in ozone are found at 16 to 29 km, with peak decreases as large as 20% found at 24 km. Integrated between 16 and 28 km, a decrease of 13-20 Dobson units is observed when the ozonesonde data after the Pinatubo eruption are compared with those prior to the eruption. The altitude at which the most pronounced ozone decrease is found strongly correlates with peak aerosol loading determined by the lidar. In addition, a small increase in ozone density is found above about 28 kin. Mechanisms that might explain the results such as heterogeneous chemistry, radiative effects, and dynamics are discussed. 1988; Newell and Selkirk, 1988; Jager and Wege, 1990]. Very little effect has been noticed near the equator [Angell, 1988; Chandra and Stolarski, 1991]. In this study, we present a set of ozonesonde measurements obtained in the tropics in 1990 and 1991. The data indicate a reduction in the amount of ozone in the lower stratosphere
Ozone in the troposphere: Measurements, climatology, budget, and trends
Atmosphere-Ocean, 2008
An improved understanding of the global tropospheric ozone budget has recently become of great interest, both in Canada and elsewhere. Improvements in both modelling and measurement have made it possible for weather centres to begin to forecast air quality using numerical weather prediction models. Despite substantial progress, there are many open questions regarding tropospheric ozone photochemistry, long-range transport and the importance of the stratospheric source; this remains an area of very active research. Since ozone in association with particulate matter causes respiratory problems in humans, trends and forecasting of future surface ozone levels are also of great importance. The current status of measurement and modelling, as well as the current understanding of tropospheric ozone budgets and trends, are reviewed, with an emphasis on Canada within the global context.
Climate Research, 1991
The response of the atmosphere to increasing emissions of radatively active trace gases (COz, CH,, N 2 0 , o3 and CFCs) is calculated by means of a l-dimensional coupled chemical-radiativetransport model. We identify the sign and magnitude of the feedback between the chemistry and thermal structure of the atmosphere by examining steady state changes in stratospheric ozone and surface temperature in response to perturbations in trace gases of anthropogenic origin. Next, we assess the possible decline in stratospheric ozone and its effect on troposphere-stratosphere temperature trends for the period covering the pre-industrial era to the present. Future trends are also considered using projected 'business-as-usual' trace gas scenario (scenario BAU) and that expected as a result of global phase-out of production of CFCs by the year 2000 (scenario MP). The numerical experiments take account of the effect of stratospheric aerosol loading due to volcanic eruptions and the influence of the thermal inertia of the ocean. Results indicate that the trace gas increase from the period 1850 to 1986 could already have contributed to a 3 to 10 % decline in stratospheric ozone and that this decline is expected to become more pronounced by the year 2050, amounting to a 43 % ozone loss at 40 km for the scenario BAU. The total column ozone Increase of 1.5 % obtained in our model calculations for the present-day atmosphere is likely to change sign with time leading to a net decrease of 12.7 % by the middle of next century. The equilibrium surface warming for the period 1850 to 1986 is found to be 0.7 K and our calculations indicate that thls warming will reach 2.6 K by the year 2050. As a result of radiativechemical interactions, a large stratospheric cooling (16.4 K) is likely by the middle of the next century. In case the control measures on production of CFCs as laid down in the London Amendment of the Montreal Protocol are implemented by all countries and a global phase-out of CFCs takes place by the year 2000, the ozone loss at 40 km could be restricted to 17 % by the year 2050 (net column decrease of only 2.9%). This would, however, only marginally reduce the stratospheric cooling to 12.6 K. The greenhouse warming at the surface expected by the middle of the next century with enforcement of the Montreal Protocol restrictions is likely to be 2 K.