A scientist from the University of Waterloo, Canada, says that an observed cyclic hole in the ozone layer provides proof of a new ozone depletion theory involving cosmic rays, a theory outlined in his recent study. Dr. Qing-Bin Lu, a professor of physics and astronomy, said it was generally accepted for more than two decades that the Earths ozone layer is depleted by chlorine atoms produced by the suns ultraviolet (UV) light-induced destruction of chlorofluorocarbons (CFCs) in the atmosphere. But mounting evidence supports a new theory that says cosmic rays, rather than the suns UV light, play the dominant role in breaking down ozone-depleting molecules and then ozone. Cosmic rays are energy particles that originate in the space.

In his study, Dr. Lu analyses reliable cosmic ray and ozone data in the period 1980-2007 which cover two full 11-year solar cycles. The data unambiguously show the time correlations between cosmic ray intensity and global ozone depletion, as well as between cosmic ray intensity and the ozone hole over the South Pole. This finding not only provides a fingerprint for the dominant role of the cosmic-ray mechanism in causing the ozone hole, but also contradicts the widely accepted photochemical theory, Dr. Lu said. These observations cannot be explained by the photochemical model. Instead, they force one to conclude that the cosmic ray mechanism plays the dominant role in causing the hole.

In the first submission of his paper to Physical Review Letters in August 2008, Dr. Lu predicted one of the severest ozone losses in 2008-2009, as a result of the cosmic ray cycle. His study quantitatively predicted that the mean total ozone in the October hole over Antarctica would be depleted to around 187 DU. The latest satellite data sets from the National Aeronautics and Space Administration (NASA) of the United States later showed that the mean total ozone in the ozone hole in October 2008 was 197 DU, within five per cent of Dr. Lus prediction.

Recent scientific assessments of ozone depletion by the World Meteorological Organization and the United Nations Environment Programme, using photochemical models, had predicted that global ozone will recover (or increase) by 1-2.5 per cent between 2000 and 2020 and that the Antarctic springtime ozone hole will shrink by 5-10 per cent between 2000 and 2020. In sharp contrast, the cosmic ray theory predicted one of the severest ozone losses over the South Pole in 2008-2009 and another large hole around 2019-2020.
Source: www.exchangemagazine.com

In the United States, new research by scientists from the National Aeronautics and Space Administration (NASA) and University of Maryland (UM) suggests that the ozone layer of the future is unlikely to look much like the past because greenhouse gases are changing the dynamics of the atmosphere.

Previous studies had shown that while the build-up of greenhouse gases makes it warmer in troposphere, it actually cools the upper stratosphere. This cooling slows the chemical reactions that deplete ozone in the upper stratosphere and allows natural ozone production in that region to outpace destruction by chlorofluorocarbons (CFCs). Accumulation of greenhouse gases also changes the circulation of stratospheric air masses from the tropics to the poles, NASA scientists note. In Earths middle latitudes, that means ozone is likely to over-recover, growing to concentrations higher than they were before the mass production of CFCs. In the tropics, stratospheric circulation changes could even prevent the ozone layer from fully recovering.

Dr. Feng Li, an atmospheric scientist at UMs Goddard Earth Sciences and Technology Centre and lead author of the study, says that circulation is just as important as cooling. It is not one process or the other, but both, he adds. The findings are based on a detailed computer model that includes atmospheric chemical effects, wind changes and solar radiation changes. Dr. Lis experiment is part of an ongoing international effort organized by the United Nations Environment Programmes Scientific Assessment Panel to assess the state of the ozone layer. Dr. Li, working with Dr. Richard Stolarski and Dr. Paul Newman of NASAs Goddard Space Flight Centre, found that greenhouse gases alter a natural circulation pattern that influences ozone distribution. The Brewer-Dobson circulation is like a pump to the stratosphere, moving ozone from the lower parts of the atmosphere, into the upper stratosphere over the tropics. Air masses then flow north or south through the stratosphere, away from the tropics towards the poles.

The Arctic would benefit from the surplus ozone in the northern hemisphere and from the overall decline of ODS to recover by 2025. The globally averaged ozone and Antarctic concentrations would catch up by 2040, as natural atmospheric production of ozone resumes. However, Dr. Lis model shows a continuing ozone deficit in the stratosphere over the tropics. In fact, when the model run ended at year 2100, the ozone layer over the tropics still showed no signs of recovery.
Source: www.sciencedaily.com

The ozone layer over Sweden was thicker in this February than it has been in decades, just a year after the second-thinnest level was recorded, the Swedish Meteorological and Hydrological Institute (SMHI) has said. Measurements taken at SMHIs Norrkoeping station showed the ozone layer was 426 Dobson units (DU) in February, the thickest since recordings there began in 1988. At the Vindeln station in northern Sweden, where measurements began in 1991, a record high of 437 DU was recorded.

We have to go as far back to the measurements taken in Uppsala between 1951 and 1966 to find levels that high, SMHI said in a statement. There, the highest level for February was in 1957, when a value of 439 DU was recorded.

The circumpolar whirl over the Arctic a polar high-pressure system formed of a distinct column of cold air that develops during the long polar night disappeared very quickly in mid-January, and the stratosphere warmed up quickly in the space of a few days, SMHI explained. As a result, the low temperatures that usually cause rapid depletion of the ozone layer did not take place, it said. The ozone layer over Sweden usually is at its thickest level during the spring, before thinning during the summer and reaching a minimum during the winter, says SMHI.
Source: www.google.com

The dominant mode of climate variability across the Southern Hemisphere is the Southern Hemisphere Annular Mode (SAM), which describes the strength of the circumpolar zonal winds. Observations and models have linked stratospheric polar ozone depletion with trends in SAM.

However, the general circulation models used in the Intergovernmental Panel on Climate Change assessment can only investigate how ozone influences atmospheric circulation, not vice versa. In the United States, scientists from Earth System Research Laboratory (ESRL) of the National Oceanic & Atmospheric Administration and Goddard Space Flight Centre of the National Aeronautics and Space Administration analysed records dating from 1962 to 2004 to investigate the two-way ozone-SAM relationship. They found a significant correlation between the austral spring total column ozone above the South Pole and SAM, with delay times of up to four months.

The austral spring SAM is also linked to polar ozone concentrations into the early summer. The ozone-SAM relationship is then investigated in a coupled chemistry climate model (CCM). Led by Dr. Ryan L. Fogt of ESRL, the scientists have shown that the observed relationship can be represented in the CCMs, suggesting CCMs are important tools to investigate future Southern Hemisphere climate change involving ozone recovery and greenhouse gas increases.
Source: www.sciencemode.com

The global market for rocket launches may need more stringent regulation in order to prevent significant damage to Earths stratospheric ozone layer in the decades to come, according to a new study by researchers in the United States. Future ozone losses from unregulated rocket launches will eventually exceed ozone losses due to chlorofluorocarbons (CFCs), said Dr. Martin Ross from The Aerospace Corporation and the chief author of the study. The study, with participation from the University of Colorado at Boulder (UCB) and Embry-Riddle Aeronautical University, provides a market analysis for estimating future ozone layer depletion based on the expected growth of the space industry and known impacts of rocket launches.

If left unregulated, rocket launches by the year 2050 could result in more ozone destruction than was ever realized by CFCs, warned Prof. Darin Toohey of UCBs atmospheric and oceanic sciences department. Since some proposed space efforts would require frequent launches of large rockets over extended periods, the new study was designed to bring attention to the issue in the hope of sparking additional research.

Current global rocket launches deplete the ozone layer by no more than a few hundredths of 1 per cent annually, said Prof. Toohey. But as the space industry grows and other ozone-depleting chemicals decline in the Earths stratosphere, the issue of ozone depletion from rocket launches would move to the forefront. Just a handful of space shuttle launches by the United States National Aeronautics and Space Administration release more ozone-depleting substances in the stratosphere than the entire annual use of CFC-based medical inhalers used to treat asthma and other diseases in the United States and which are now banned, said Prof. Toohey.

Highly reactive trace-gas molecules known as radicals dominate stratospheric ozone destruction a single radical in the stratosphere can destroy up to 10,000 ozone molecules. Microscopic particles, including soot and aluminium oxide particles emitted by rocket engines, provide chemically active surface areas that increase the rate such radicals leak from their reservoirs and contribute to ozone destruction, said Prof. Toohey.

The research team is optimistic that a solution to the problem exists. We have the resources, we have the expertise, and we now have the regulatory history to address the issue in a very powerful way, he said.
Source: www.sciencedaily.com