The equal vertical scales in each panel allow direct comparisons of ozone and EESC changes between regions. Essentially all of the ozone decrease in the Antarctic and usually about 50% of the decrease in the Arctic each year are Cookies are used to help distinguish between humans and bots on contact forms on this Carbon dioxide concentrations continue to increase in the atmosphere primarily as the result of burning fossil fuels (coal, oil, and natural gas) for energy and transportation, as well as from cement manufacturing. Some reactive gases act as chemical reservoirs which can then be converted into the most reactive gases, namely ClO and BrO. 1990s. However, it is only after midcentury that the abundance of ODSs is expected to fall to values that were present before the Antarctic ozone hole was first observed in the early 1980s, due to the long atmospheric lifetime of these gases. There is evidence Two important measures are the globally averaged total column ozone (see Q3) as well as total ozone in the Antarctic during October (the month of peak ozone depletion). other gases (see Figure Q17-2). year at a time near the peak of ozone depletion, as defined by the dates shown in each occurring. The world-avoided scenario is derived by assuming that emissions of ODSs in the baseline scenario increase beyond 1987 values at a 3% annual growth rate. The abundance of halon-1301, on the other hand, has increased by 23% since 1998 and is expected to continue to increase very slightly into the next decade because of continued small releases and a long atmospheric lifetime (see Figure Q15-1). Halogen source gases such as methyl chloride (CH3Cl) that have predominantly natural sources are not classified as ODSs. atmosphere directly above that location. By late winter (September), a remarkable change in the composition of the Antarctic stratosphere has taken place. The depletion of stratospheric ozone leads to an increase in solar ultraviolet radiation at Earth’s surface. Finally, increases in In the ODP-weighted scenario, the sum of emissions is expressed as CFC-11-equivalent emissions because CFC-11 is the reference gas, with an assigned ODP value of 1. Chemical reactions on the surface of sulfate aerosol particles destroy stratospheric ozone by increasing the abundance of chlorine monoxide (ClO), a highly reactive chlorine gas (see Q7). The dots on each curve mark the occurrences of 1980 values of total The baseline scenario is labeled “From observed ODS abundances” in Figure Q18-1 since, for 1960–2016, the emissions are based upon analysis of observed abundances of the principal ODS gases at Earth’s surface (see Figure Q15-1). A gigatonne = 1 billion (109) metric tons = 1 trillion (1012) kilograms. When The observed record of global total ozone follows the same general tendencies of the EESC attribution curve over the past half century, providing strong evidence that changes in stratospheric halogens in response to human activities are the primary factor responsible for the long-term variation of ozone depletion. HFCs are replacement compounds for ODSs that were chosen because they contain no chlorine or bromine that cause ozone depletion. months somewhere in the Antarctic, and The principal CFCs are CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (CCl2FCClF2). approaching its maximum (see Q13). In Science, we are due to look at properties of materials. The wide range of possible future levels of CO2, CH4, and N2O is an important limitation to providing accurate future projections of total column ozone. Identifying an ozone increase that is attributable to the observed decrease in the amount of ODSs is challenging because Observations show that halogen source gases and reactive halogen gases are present in the chlorine (EESC) for the midlatitude, This week the sessions focus on rounding decimals. Based on the ozone increases in the chemistry-climate model projections, clear-sky UV-B radiation is expected to be substantially below the 1960 value by the end of the century across much of the globe. In the early 1990s, global total ozone was depleted by 5% relative to the 1964–1980 average, the maximum depletion observed during the modern instrument era. Most of the HCl in the explosive plume of Mount Pinatubo did not enter the stratosphere because of this scavenging by precipitation. After 1982, Please encourage children to do their own research and display ideas in creative ways. Ozone Long-term surface UV changes. The 2013 Intergovernmental Panel on Climate Change (IPCC) climate assessment concluded that stratospheric ozone depletion most likely caused a slight cooling of Earth’s surface, as shown in Figure Q17-1. For example, the abundances of ODSs with short lifetimes, such as methyl chloroform, respond quickly to emission reductions, whereas the abundances of ODSs with long lifetimes such as CFC-11 respond slowly to emission reductions. due to the combined effects of ODSs and the eruption of Mount Pinatubo (see Figure Q12-1). increase in the quantity termed stratospheric aerosol optical depth. If children would like to do some art this week, the following videos give step by step instructions about how to draw different objects and figures. years 2001, 2002, and 2003. the CO2-equivalent emission unit means release of a GHG would result in the same amount of RF of climate as release of the same mass of CO2, over a They do not need to complete all of it: the idea is that children can be creative and be introduced to planning and organising money in a fun way that they can be in charge of. polar night and other periods of darkness, ozone cannot be ozone destruction reactions, particularly those The GWPs shown here are evaluated for a 100-year time interval after emission. I have included 2 projects that may wish to complete instead which involve a number of skills and allow children to be creative and make their own decisions. Tropospheric air is the “air we breathe” and, as such, excess ozone in the troposphere has harmful consequences (see Q2). Total available chlorine (see red line in Figure Q7-2) is the sum of chlorine contained in halogen source gases (e.g., CFC-11, CFC-12) and in the reactive gases (e.g., HCl, ClONO2, and ClO). The ODP of CFC-11 and the GWP of carbon dioxide are assigned reference values of 1. the troposphere and stratosphere. As the atmospheric abundance of ODSs With these weightings, emissions are expressed as CFC-11-equivalent or CO2-equivalent mass per year. Reactive hydrogen and reactive nitrogen gases, for example, are involved in catalytic ozone-destruction cycles, similar to those described above, that also take place in the stratosphere. Other non-halogen gases. cause climate change exacerbate this shift in the summertime tropospheric circulation in the Southern Hemisphere, ozone As explained below, HFCs are greenhouses gases (GHGs) which warm climate and do not cause ozone depletion. The size and maximum ozone depletion (depth) of the ozone hole from 2003 through 2017 returned to values similar to oxygen atom collides with another oxygen molecule These analyses show that under certain conditions chlorine Afternoon Learning-Climate Change-Week Beginning 27th April. Instead, stratospheric volcanic aerosol has been quite low since 1995, a period of time over which global total ozone has been about 2-3% below the pre-1980 value. Overall halocarbon radiative forcing, however, is slowly increasing because of growing contributions from non-ODS gases (HFCs, PFCs, and SF6). In such years, winter minimum temperatures Surface UV-B radiation. The values are based upon ClO with O to form Cl and O2. Over the next 2 days could children please research the island of Heimaey, Iceland and find out about a volcanic eruption that happened there. Most UV-B radiation emitted by the Sun is absorbed by the ozone layer; the rest reaches Earth’s surface. The emissions, when weighted by their potential to destroy ozone, peaked in the This radiative forcing due to stratospheric ozone depletion will diminish in the coming decades, as ODSs are gradually removed from the atmosphere. (A megatonne = 1 million (106) metric tons = 1 billion (109) kilograms. Individual ODS reductions. At geographic locations with the lowest total ozone values, balloon measurements show that the chemical destruction of ozone has often been complete over an altitude region of up to several kilometers. These compounds ozone and EESC. many locations over the globe, regular measurements Greenhouse gases and the radiative forcing of climate. In this way, one Cl atom participates in many cycles, destroying many ozone molecules. When global total ozone There are indications of a decline in surface UV-B at a few surface monitoring stations in the Northern Hemisphere since 1994, a period coincident with the rise in global total ozone (see Figure Q12-1). Antarctic total ozone. Note the large difference in the vertical scales: total chlorine entering the stratosphere A large fraction of total reactive bromine is generally in the form of BrO, whereas usually only a small fraction of total reactive chlorine is in the form of ClO. Conversely, the high latitudes. The abundances of most HCFCs, which are used as transitional substances to replace CFCs, will likely continue to increase in the next one to two decades before production and consumption are Many programs around the globe have been successful in reducing or limiting the emission of pollutants that cause production of excess ozone near Earth’s surface. Eruption plumes also contain a considerable amount of water vapor, which forms rainwater and ice in the rising fresh plume. In 2009, the Montreal Protocol became the first multilateral environmental agreement to achieve universal ratification. well as 60°S to 60°N latitude (global panel) for the time period 1960–2100. With little reactive halogen available, total ozone depletion in this region is also very small. while global ozone declined, and since the late 1990s EESC has declined and global ozone has risen. Low energy UV radiation, UV-A, which is not absorbed significantly by the ozone layer, causes premature aging of the skin. harm to ozone. are gradually removed from the atmosphere (see Figure Q15-1). on the ground, aircraft, high-altitude balloons, and emissions are based upon an analysis of atmospheric observations up to 2013 and projections to 2100 that represent an upper The abundance of halon-1301 has nearly peaked and is expected to decline in coming decades. The bottom panel of Figure Q13-1 compares the observed long-term record of global total ozone (red line) to the variation in ozone attributed to the changes in EESC (black dashed line). Prior to 1960, the amount of reactive halogen gases in the stratosphere was insufficient to cause significant chemical loss of Antarctic ozone. The first decreases in Antarctic total ozone were observed in the early 1980s over research stations located on the Antarctic The influence of climate change on future ozone in Figure Q20-2 as discussed above was derived using a particular GHG emission scenario, termed RCP 6.0. The large regions of low total ozone in 1997 and and the tropics, total ozone returns to 1960 values by midcentury, which is earlier than expected from the decrease in EESC The amount of ozone depletion depends on both the mass of sulfate aerosol produced following the eruption and the value of EESC (see Q15). Ozone destruction Cycle 1 is illustrated in Figure Q8-1. destroyed by these reactions. Complete the Joe Wicks workout https://www.youtube.com/watch?v=Rz0go1pTda8. HFCs, used as ODS Ozone changes are routinely monitored by a large group of investigators using satellite, airborne, and ground-based instruments. (ODSs); all ODSs contain at least one chlorine completely phased out. Explosive volcanic eruptions in the last three decades have not caused the Antarctic ozone hole and, as noted above, have not been sufficient to cause the long-term depletion of global total ozone. that in the Antarctic. https://whiterosemaths.com/homelearning/year-5/. Low temperatures are important because they allow liquid and solid PSCs to form. In the troposphere (below about 12 km), all that these maximum values and their geographic extent have significantly diminished since the 1970s. The abundance of EESC will remain high for much of the 21st century due to the long atmospheric lifetime of ODSs (see Q15-1). equipment using low-GWP refrigerants is optimized. The depletion is attributable to chemical destruction by reactive halogen gases (see Q7 and Q8), which increased everywhere in the stratosphere in the latter half of the 20th century (see Q15). Ozone Depletion Potentials and Global Warming Potentials. 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