Feb 5 Lec 9 .docx

ENV 200 Feb 5, 2013 Ozone  Pollutant in troposphere: -Ground level ozone (bad) -Results from secondary reactions (doesn’t come out of cars directly) of air pollutants and contributes to smog formation in urban center -NOx (nitrogen & oxygen) +VOCs (volatile organic compounds) produce O3 in the presence of sunlight -Adversely affect crop and forest vegetation, human respiratory health  Ozone: Naturally produced component in the stratosphere -Shields Earth’s surface from UV radiation, and therefore essential -In 1976 thinning of ozone over Antarctica and hit record low levels in 2000 Effects of Ozone depletion  More UV radiation reaches Earth  Damage to ecosystems  Human health problems -More cataracts, skin cancer, weakened immunity  Breaks down plant material, hinder processes Causes of Ozone thinning  CFC’s (Chlorofluorocarbons), halons, industrial solvents (refrigeration systems)  First used in 1960s  These chemicals were cheap and easy to produce  Were eventually banned Recovery of the Ozone Layer  1987 Montreal Protocol- phase ouf CFC’s  By 2007, 191 countries participating  Industry substitutes such as hydro fluorocarbons do not attack ozone but are potent greenhouse gases  Most countries have phased out CCFC’s  Long residence time (est~70-100 yrs)  “The single most successful international agreement to date” Unprecedented ozone hole opens over Canadian Arctic  Arctic ozone hole covering 2 million km squared reported in spring 2011 (Nature)  The hole initially formed over the Arctic, then spread across northern Canada, northern Europe and Central Russia to northern Asia  A cooling trend in the stratosphere?, is thought to be tied to increasing greenhouse gases like carbon dioxide, and could create more ozone holes Sidebar  Environment Canada not being allowed to discuss the discovery with the media  Co-author is one of several Environment Canada ozone scientists who have received letters of warning of possible “discontinuance of job function” as part of the downsizing underway  Censor what employees can tell public, massive layoffs (ozone monitoring) Climate Change: Weather and Climate Weather  Atmospheric conditions at a specific place and time  Rapid changes Climate  Average long-term weather conditions  Changes over hundreds/thousands of years  Important factors: temperature and precipitation How do we currently understand the climate paradigm?  Earth’s climate system is “inherently chaotic, sensitively balanced, and threshold-laden”  The latest peer-reviewed paleoclimatic studi