It was originally believed by Molina and Rowland that ozone depletion by chlorine radical could only occur in the upper atmosphere where there is plenty of free oxygen present13
Stratospheric Ozone Depletion by Chlorofluorocarbons (Nobel Lecture)
Schematic illustration of the distribution of chlorine among various chemical forms after release to the atmosphere in the form of methyl chloride (CH3Cl). The combination of very large springtime losses of ozone over Antarctica directly attributable to manmade chlorine compounds introduced into the stratosphere, and measurable ozone losses in the north temperate zone, brought a rapid change in the attitudes of CFC-producers and many of the users, and a complete phaseout of CFC production and uses became a widely accepted goal
I have proposed elsewhere that a more active sun produces more ozone destroying chemical reactions above 45km ro reduce ozone there and thereby cool that part of the atmospheric column and that furthermore that process dominates over the better known ozone creation processes below 45km when the sun is more active so as to overall produce a reverse sign temperature response in the mesosphere and stratosphere i.e. Because ozone depletes at temperatures colder than -108 degrees Fahrenheit (-78 degrees Celsius), the warm air helped protect the thin layer about 16 miles (25 kilometers) above our heads
CFCs escaping from airconditioners and refrigerators in the nothern hemisphere sneaking down to the antarctic where these rather heavy molecules were magically lifted up against gravity to go up into the stratosphere where they were disassociated into chlorine atoms while ocean spray chlorine ions were washed out of the atmosphere by rain just like the chlorine atoms injected into the stratosphere by an active volcano down there. Surely, if we calculate the volume of ozone in the collar we could see if it can be distributed over the hole demonstrating how much, if any, ozone has been actually lost
Acid Rain, Ozone Depletion, Global Warming
Look what happened to the Earth Summit and look at the prosperity the US economy experienced under the Clinton Administration and still did nothing to decrease the CO2 levels in the states fearing it will hurt the economy. The studies also show that the amount of acid rain formed and deposited is not enough to cause the streams and lakes in these regions to be devoid of fish
Without going into too much detail, these reactions involve methane and nitrogen dioxide, which should temporarily tie up the Cl released from CFC's (or the ClO produced along the way; see reactions 2 and 3, above). (You might remember people thought the same thing about DDT at first?) As their name suggests, they are molecules consisting of chlorine, fluorine, and carbon
Perhaps decades from now, participants in the Kyoto Protocol, the global-warming treaty modeled after the Montreal Protocol, will meet and congratulate themselves because none of their scary assertions came true. National Cancer Institute statistics show that malignant melanoma incidence and mortality, which had been undergoing a long-term increase that predates ozone depletion, has actually been leveling off during the putative ozone crisis
Similarly, by ending production of ozone depleters, we allow natural processes to remove excess chlorine and bromine, which slows the ozone destruction reactions to normal speeds, and the production process will have the chance to restore the ozone layer to normal levels. It makes sense to explore the questions in reverse order, but understanding either answer requires some basic facts about how ozone levels remain relatively constant and what ozone depletion means
Ozone Home Page
Data from the WMO-GAW ozone observing system are collected and stored at the WMO World Ozone and Ultraviolet Radiation Data Centre (WOUDC) at Environment Canada, Toronto. The ozone that occurs naturally near the surface and in the lower atmosphere is also beneficial because ozone helps remove pollutants from the atmosphere
WebLessons: Fixing the Ozone Hole
What is the relationship between the temperature in the Antarctic and the size of the ozone hole? Answer: When the temperatures drop to their lowest levels, more ozone is destroyed, so the hole gets larger. Why was the ozone layer getting thin? What caused the hole? How big is it today? What are people doing to stop it? You will explore this scientific puzzle in this lesson, and you will find out how you can help protect the ozone
The hole occurs over Antarctica because the extreme cold helps the very high clouds characteristic of that area form tiny ice particles of water and nitric acid, which facilitate the chemical reactions involved. When the Antarctic spring sun rises in August or September and hits the trapped chemicals, a chain reaction begins in which chlorine, bromine (from the halons), and ice crystals react with the ozone and destroy it very quickly
Is the ozone layer on the road to recovery?
New research findings reveal how wildfires spread July 21, 2015 Evidence presented in a recently released study, authored by a team of scientists from the USDA Forest Service, University of Maryland and University of Kentucky, reveals new findings about how wildfires actually spread and ... Over the Arctic, the effect is far less pronounced because the northern hemisphere's irregular landmasses and mountains normally prevent the build-up of strong circumpolar winds
They released scientific balloons, known as ozone sondes, which make hundreds of measurements on their way from the ground to 30 km up in the atmosphere. Extreme and prolonged cold in the stratosphere last winter and spring speed up and enhanced the chemical reactions that destroy the ozone, says co-author Michelle Santee, of the Jet propulsion Laboratory at the California Institute for Technology
The Antarctic Ozone Hole
If there is a hole in the ozone layer then this means that more harmful ultra-violet rays get through than are good for us or many other life forms, plant or animal. They are a group of chemically similar gases used in refrigeration systems, air conditioners, aerosols, solvents and in the production of some types of packaging
But since the Montreal Protocol agreement in 1987, the emissions of these chemicals have been in decline, as ozone-friendly alternative chemicals have come into common usage.Exactly what impact this regulation had on the size of the hole was not clear until now, largely because it also fluctuates as a result of temperature and other variables. Although it's on the mend, Jon Shanklin of the British Antarctic Survey, who was one of the three discoverers, said the lesson is telling -- and pretty brutal."Yes, an international treaty was established fairly quickly to deal with the ozone hole," he told the Guardian recently
But in terms of what happened in Antarctica, which is where the biggest changes were, the ozone levels were about a third of what they were in the 1990s compared to what they were in the 1970s. However, the significant increase in CFCs last century, commonly found in aerosols, refrigerators, air conditioners, cars and food packaging, started to burn a hole in it
Whatever Happened to the Ozone Hole?
But in May 1985 scientists with the British Antarctic Survey shocked the world when they announced the discovery of a huge hole in the ozone layer over Antarctica. These UV rays can cause skin cancer and cataracts in humans, as well as reproductive problems in fish, crabs, frogs, and even in the single-celled phytoplankton at the bottom of the ocean food chain
World of Change: Antarctic Ozone Hole : Feature Articles
On the other hand, because of the impact of greenhouse gas warming, the ozone layer over the tropics and mid-southern latitudes may not recover for more than a century, and perhaps not ever. Models suggest that the concentration of chlorine and other ozone-depleting substances in the stratosphere will not return to pre-1980 levels until the middle decades of this century
The value of 220 Dobson Units is chosen since total ozone values of less than 220 Dobson Units were not found in the historic observations over Antarctica prior to 1979. What is the ozone hole? Each year for the past few decades during the Southern Hemisphere spring, chemical reactions involving chlorine and bromine cause ozone in the southern polar region to be destroyed rapidly and severely
The Ozone Layer Fact Sheet
They are more frequently seen from the southern hemisphere, particularly from locations along the Antarctic Peninsula where the mountains create lee-waves in the upper atmosphere
The Ozone Hole
Scientific theory and evidence suggest that, once emitted to the atmosphere, these compounds could significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation. The Ozone Hole About Us Awards Donate Contact Us Site Map News Links Ozone Hole History Montreal Protocol Ozone Hole 2006 Ozone hole 2014 Arctic Ozone Hole The Ozone Hole For nearly a billion years, ozone molecules in the atmosphere have protected life on Earth from the effects of ultraviolet rays
No comments:
Post a Comment