Scientific Assessment Of Ozone Depletion Research Articles

INTRODUCTION: Methyl bromide primer and timeline

INTRODUCTION: Methyl bromide primer and timeline

Observation-based assessment of stratospheric fractional release, lifetimes, and ozone depletion potentials of ten important source gases

Abstract. Estimates of the recovery time of stratospheric ozone heavily rely on the exact knowledge of the processes that lead to the decomposition of the relevant halogenated source gases. Crucial parameters in this context are fractional release factors (FRFs) as well as stratospheric lifetimes and ozone depletion potentials (ODPs). We here present data from the analysis of air samples collected between 2009 and 2011 on board research aircraft flying in the mid- and high-latitude stratosphere and infer the above-mentioned parameters for ten major source gases: CFCl3 (CFC-11), CF2Cl2 (CFC-12), CF2ClCFCl2 (CFC-113), CCl4 (carbon tetrachloride), CH3CCl3 (methyl chloroform), CHF2Cl (HCFC-22), CH3CFCl2 (HCFC-141b), CH3CF2Cl (HCFC-142b), CF2ClBr (H-1211), and CF3Br (H-1301). The inferred correlations of their FRFs with mean ages of air reveal less decomposition as compared to previous studies for most compounds. When using the calculated set of FRFs to infer equivalent stratospheric chlorine, we find a reduction of more than 20% as compared to the values inferred in the most recent Scientific Assessment of Ozone Depletion by the World Meteorological Organisation (WMO, 2011). We also note that FRFs and their correlations with mean age are not generally time-independent as often assumed. The stratospheric lifetimes were calculated relative to that of CFC-11. Within our uncertainties the ratios between stratospheric lifetimes inferred here agree with the values in recent WMO reports except for CFC-11, CFC-12 and CH3CCl3. Finally, we calculate lower ODPs than recommended by WMO for six out of ten compounds, with changes most pronounced for the three HCFCs. Collectively these newly calculated values may have important implications for the severity and recovery time of stratospheric ozone loss.

Estimates of past and future ozone trends from multimodel simulations using a flexible smoothing spline methodology

A novel additive model analysis of multimodel trends is presented. The approach is motivated by, and particularly suited to, the analysis of multimodel time series of varying length. This Time series Additive Model (TSAM) approach consists of three distinct steps: estimation of individual model trends, baseline adjustment of the trends, and the weighted combination of the individual model trends to produce a multimodel trend (MMT) estimate. The baseline adjustment step is not an essential ingredient of the TSAM but is included to reduce model spread. The association of the TSAM approach with a probabilistic model allows trend estimates to be used to make formal inference (e.g., calculation of confidence and prediction intervals). The method is applied to the analysis of multimodel ozone time series of varying lengths as were considered for the 2006 Scientific Assessment of Ozone Depletion. The advantages of the TSAM approach are demonstrated to include the production of smooth trend estimates out to the ends of the time series, the ability to model explicitly interannual variability about the trend estimate, and the ability to make rigorous probability statements. Calculated ozone return dates are consistent with previous qualitative estimates, but the more quantitative analysis provided by the MMT is expected to allow such data sets to be better utilized by the community and policy makers.

Impact of sudden Arctic sea‐ice loss on stratospheric polar ozone recovery

We investigate the sensitivity of Northern Hemisphere polar ozone recovery to a scenario in which there is rapid loss of Arctic summer sea ice in the first half of the 21st century. The issue is addressed by coupling a chemistry climate model to an ocean general circulation model and performing simulations of ozone recovery with, and without, an external perturbation designed to cause a rapid and complete loss of summertime Arctic sea ice. Under this extreme perturbation, the stratospheric response takes the form of a springtime polar cooling which is dynamical rather than radiative in origin, and is caused by reduced wave forcing from the troposphere. The response lags the onset of the sea‐ice perturbation by about one decade and lasts for more than two decades, and is associated with an enhanced weakening of the North Atlantic meridional overturning circulation. The stratospheric dynamical response leads to a 10 DU reduction in polar column ozone, which is statistically robust. While this represents a modest loss, it has the potential to induce a delay of roughly one decade in Arctic ozone recovery estimates made in the 2006 Scientific Assessment of Ozone Depletion.

Climate Change and Drying of Agricultural Products

Global warming is affecting the world and will continue to affect humans and the ecosystem in the future, in different regions of the earth in diverse ways: air temperature rise, modifications in the precipitation and snow/ice melting rates, sea level rise, changes in geographical distribution, and even extinction of some plants and animals. In particular, the predictions presented in the 2007 Report of the Intergovernmental Panel on Climate Change, Working Group 1 (available at www.ipcc.ch) for the mean temperature increase in the present century is about (3 ± 1)°C/century for a middle range scenario of human behavior. Mitigation measures need to be taken urgently in all aspects of activities in order to reduce the future impact of the temperature augmentation. In particular, the drying process (as well as the pre- and post-drying operations) needs to be reanalyzed, in order to try to participate in this world effort to reduce the impact of anthropogenic activities that introduce in the atmosphere an excess of greenhouse gases (GHG). The energy savings, use of renewable energies, optimization of each part of the drying process, and use of control devices for detecting and minimizing the atmospheric injection of GHG are some of a large number of possible actions to be taken in this respect. A nice example of how a planetary problem can be solved with the global participation of scientists, professionals, authorities and general public is the stopping of the destruction of the ozone layer and its possible recuperation in the near future, as discussed in the WMO related report (“Scientific Assessment of Ozone Depletion: 2006”, that can be obtained at http://www.wmo.int/pages/prog/arep/gaw/ozone2006/ozoneasstreport.html).[ 10 ]

Technical Note: The CCCma third generation AGCM and its extension into the middle atmosphere

Abstract. The Canadian Centre for Climate Modelling and Analysis third generation atmospheric general circulation model (AGCM3) is described. The discussion summarizes the details of the complete physics package emphasizing the changes made relative to the second generation version of the model. AGCM3 is the underlying model for applications which include the IPCC fourth assessment, coupled atmosphere-ocean seasonal forecasting, the first generation of the CCCma earth system model (CanESM1), and middle-atmosphere chemistry-climate modelling (CCM). Here we shall focus on issues related to an upwardly extended version of AGCM3, the Canadian Middle-Atmosphere Model (CMAM). The CCM version of CMAM participated in the 2006 WMO/UNEP Scientific Assessment of Ozone Depletion and issues concerning its climate such as the impact of gravity-wave drag, the modelling of a spontaneous QBO, and the seasonality of the breakdown of the Southern Hemisphere polar vortex are discussed here.

Global modeling of biogenic bromocarbons

A global three‐dimensional chemical transport model has been used to simulate atmospheric bromoform using a variety of prescribed surface emission scenarios and a simple atmospheric chemistry scheme. Model simulations indicate that global emissions of bromoform calculated previously using top‐down methods are too low, and emissions are likely to be significantly larger than suggested in the World Meteorological Organization's reports on the Scientific Assessment of Ozone Depletion of 1998 and 2002. Our simulations suggest that global emissions of bromoform are in the range of 400–600 GgCHBr3/yr and that a large proportion of emissions are situated in tropical regions. Both these factors are likely to have an important influence on estimates of the quantity of bromine transported from the surface to the lower stratosphere by short‐lived bromocarbon species and its subsequent impact on ozone in this region. Further simulations including methyl bromide, bromoform and the other major short‐lived bromocarbons emitted from the ocean (CH2Br2, CH2BrCl, CHBr2Cl, CHBrCl2) provide estimates on the amount of reactive bromine in the troposphere and lower stratosphere derived from these compounds.

Climate change and skin cancer.

Depletion of the ozone layer and climate change by the increasing greenhouse effect are distinctly different processes. It is becoming quite clear, however, that the two global environmental problems are interlinked in several ways [D. L. Albritton, P. J Aucamp, G. Mégie, R. T. Watson, Scientific Assessment of Ozone Depletion, 1998, World Meteorological Organization, Global Ozone Research and Monitoring Project, Report No. 44 (WMO, Geneva, 1998)]. In the present analysis we deal with the possibility of such an interlinkage within one effect on human health, namely, skin cancer. The increase in the incidence of skin cancer is one of the most extensively studied effects of increasing ultraviolet radiation by ozone depletion (F. R. de Gruijl, Skin cancer and solar radiation, Eur. J Cancer, 1999, 35, 2003-2009). We wondered if this impact could also be influenced by increasing environmental temperatures. Here we show that it is likely that such an influence will occur. For the same reason, it is likely that the baseline incidence of skin cancer will be augmented by rising temperatures, which may become significant in magnitude.

Industrial Non-Energy, Non-CO 2 Greenhouse Gas Emissions

In this article we project emissions of three groups of greenhouse gases—perfluorocarbons (PFCs), sulphur hexafluoride (SF 6), and hydrofluorocarbons (HFCs)—through the year 2100. These gases were added to the gases CO 2, CH 4 and N 2O under the 1997 Kyoto Protocol to the United Nations Framework Convention on Climate Change. The emission projections are based on the projections for population and GDP, as well as the qualitative descriptions of the four storylines (A1, A2, B1, and B2) developed within an international, interdisciplinary effort to formulate new greenhouse gas (GHG) emission scenarios reported in this issue. To cover industrial non-energy, non-CO 2 greenhouse gases, emission projections of N 2O from the production of adipic acid were also calculated. Emission trajectories for CFCs, HCFCs, halons, carbon tetrachloride, methyl chloroform and methyl bromide were included by directly using the Montreal Protocol scenario (A3) from the 1998 Scientific Assessment of Ozone Depletion. There are three main ways of estimating the future trends for the emissions of the greenhouse gases discussed in this article: the increases could be linear, they could follow an S-curve, or they could be exponential, proportional to GDP development. This article refers to existing studies using these methods and integrates them. The result of the calculations shows that the total emission range for the industrial non-energy, non-CO 2 greenhouse gases is within 0.5–1.3 GtC in the period 2010–2100, when total emissions of CFCs and HCFCs are low.

Ozone layer is on slow road to recovery new science assessment indicates

The good news, according to a new report about ozone depletion, is that the ozone layer will recover in 50 years—if parties to the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer fully adhere to the treaty, and if other conditions that could affect the atmosphere remain stable.The “Scientific Assessment of Ozone Depletion: 1998,” a report prepared by the scientific assessment panel of the Montreal Protocol, states, “The stratospheric abundance of halogenated ozone‐depleting substances is expected to return to its pre‐1980 (that is, “unperturbed”) level of 2 ppb chlorine equivalent by about 2050 assuming full compliance with the Montreal Protocol and its Amendments and Adjustments.”