Ozongat groter dan ooit gemeten

SCIENTISTS FIND ANTARCTIC OZONE HOLE TO RECOVER LATER THAN EXPECTED
June 29, 2006
Bron : earthobservatory.nasa.gov

Scientists from NASA and other agencies have concluded that the ozone hole over the Antarctic will recover around 2068, nearly 20 years later than previously believed.

Researchers from NASA, the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR) have developed a new tool, a math-based computer model, to predict the timing of ozone hole recovery. Their findings will be published tomorrow in Geophysical Research Letters.

The Antarctic ozone hole is a massive loss of ozone that occurs each spring in the Southern Hemisphere. The ozone hole is caused by chlorine and bromine gases in the stratosphere, an upper layer of the atmosphere, that destroy ozone in an annually recurring process that takes place in the unique meteorological conditions of the Antarctic stratosphere. Those gases come from human-produced chemicals such as chlorofluorocarbons.

"The Antarctic ozone hole is the poster child of ozone loss in our atmosphere," said lead author Paul Newman, a research scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "Over areas that are farther from the poles like Africa or the continental U.S., the annually averaged levels of upper atmospheric ozone are only three to six percent below natural levels. But, over Antarctica, ozone is 70 percent lower in the spring. This new method allows us to more accurately estimate ozone-depleting gases over Antarctica, and how they will decrease over time, reducing the ozone hole area."

For the first time, a model combines estimates of future Antarctic chlorine and bromine levels based on current amounts as captured from NASA satellite observations, NOAA ground-level observations, NCAR airplane-based observations, with anticipated future emissions, the time it takes for the transport of those emissions into the Antarctic stratosphere, and assessments of future weather patterns over Antarctica.

The model accurately reproduces the ozone hole area in the Antarctic stratosphere over the past 27 years. Using the model, the researchers predict that the ozone hole will recover in 2068, not in 2050 as currently believed.

International agreements such as the Montreal Protocol, approved in 1987, limit production of ozone-depleting substances. Later changes to those international agreements have completely eliminated legal production of most of these chemicals, though there will be continued emissions of previously produced and stored amounts of those chemicals that are not destroyed or recycled.

The researchers also show that the ozone hole has not yet started to significantly shrink, something they predict will not start to occur until 2018. Newman's team also further indicated that greenhouse gas-forced climate change will have only a small impact on the Antarctic stratosphere and recovery of the ozone hole.

The upper ozone layer is important because it blocks 90-99 percent of the sun's ultraviolet radiation from making contact with Earth. This solar radiation can cause skin cancer, genetic damage, eye damage and can impact marine life.

"My job is to track ozone-depleting chlorofluorocarbons around the globe on a weekly basis," said Steven Montzka, a research chemist in the Global Monitoring Division at NOAA's Earth Systems Research Laboratory in Boulder, and co-author of the paper. "We make calculations with that information to determine how gases containing chlorine and bromine that have life spans in the atmosphere ranging from 45 to about 300 years, are affecting ozone. This new prediction model is a very useful step forward to refining our understanding of ozone hole recovery time scales."

The researchers included ozone data from the Total Ozone Mapping Spectrometer (TOMS) on NASA's Earth Probe TOMS satellite, gas measurements from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite, temperature information from NOAA's polar orbiting series satellites, and data captured by NOAA ground stations and weather balloons to create the new prediction model.

To view related Antarctic ozone hole images on the Web, visit:

http://www.nasa.gov/cente(...)/ozone_recovery.html

For more information about the Antarctic ozone hole on the Web, visit:

http://ozonewatch.gsfc.nasa.gov/

Drugshond	donderdag 28 december 2006 @ 19:58
	Ozongat groter dan ooit gemeten Bron : KNMI 30 oktober 2006 - Het ozongat boven het Zuidpoolgebied is dit jaar groter dan ooit werd gemeten. Dit volgt uit de meetreeks van de satellietinstrumenten GOME, SCIAMACHY en OMI. Tijdreeksen ozonverlies boven het Zuidpoolgebied over de afgelopen 10 jaar in megaton ozongas In de analyse van het KNMI was op 1 oktober het ozonverlies groter dan het record in het jaar 2000. Eerder berichtten we al dat het ozonverlies op 25 en 26 september even groot als het record gemeten in het jaar 2000. Ook de Wereld Meteorologische Organisatie maakt hier nu melding van. Het ozonverlies is de maat voor de hoeveelheid ozon die is afgebroken in het ozongat, en wordt bepaald door zowel het oppervlak als de diepte van het ozongat. Het KNMI meet sinds 1995 de dikte van de ozonlaag met de satellietinstrumenten GOME, SCIAMACHY (sinds 2002) en OMI (sinds 2005). Het KNMI coördineert de kwaliteitscontrole van de metingen met het SCIAMACHY instrument. OMI is een Nederlands-Fins instrument, waarvan het KNMI de wetenschappelijke leiding heeft. Hoe ontstaat het ozongat ? Het ozongat ontstaat sinds de jaren tachtig van de vorige eeuw jaarlijks in de lente (bij ons is het dan herfst) boven het Zuidpoolgebied. Het ozongat ontstaat doordat ozon wordt afgebroken door het chloor dat afkomstig is uit chloorfluorkoolstoffen (CFK’s), die vroeger werden gebruikt in onder meer spuitbussen en koelkasten. Voor de snelle afbraak van ozon moet het zeer koud zijn en is zonlicht nodig. Aan deze voorwaarden wordt in het vroege voorjaar op de Zuidpool voldaan. Dit jaar is de temperatuur in het ozongat boven het Zuidpoolgebied lager dan ooit sinds het begin van de satellietmetingen in 1979, wat het extreme ozonverlies van dit jaar mede verklaart. Herstel op termijn ? CFK’s worden sinds eind jaren tachtig nauwelijks meer gebruikt en de hoeveelheid CFK’s in de atmosfeer neemt al enkele jaren langzaam af. De verwachting is dan ook dat het ozongat in de loop van deze eeuw zal herstellen. Het herstel wordt echter vertraagd door een geleidelijke afname van de temperatuur in de ozonlaag, die het gevolg is van het door de mens veroorzaakte broeikaseffect. Dit effect leidt tot hogere temperaturen nabij het aardoppervlak, maar juist tot lagere temperaturen op de hoogten van 10 tot 25 km waar de ozonlaag zich bevindt. Ook al zal op termijn het ozongat naar verwachting weer herstellen, het uitzonderlijk grote ozonverlies van dit jaar maakt duidelijk dat van een begin van herstel van het ozongat nog allerminst sprake is. quote: SCIENTISTS FIND ANTARCTIC OZONE HOLE TO RECOVER LATER THAN EXPECTED June 29, 2006 Bron : earthobservatory.nasa.gov Scientists from NASA and other agencies have concluded that the ozone hole over the Antarctic will recover around 2068, nearly 20 years later than previously believed. Researchers from NASA, the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR) have developed a new tool, a math-based computer model, to predict the timing of ozone hole recovery. Their findings will be published tomorrow in Geophysical Research Letters. The Antarctic ozone hole is a massive loss of ozone that occurs each spring in the Southern Hemisphere. The ozone hole is caused by chlorine and bromine gases in the stratosphere, an upper layer of the atmosphere, that destroy ozone in an annually recurring process that takes place in the unique meteorological conditions of the Antarctic stratosphere. Those gases come from human-produced chemicals such as chlorofluorocarbons. "The Antarctic ozone hole is the poster child of ozone loss in our atmosphere," said lead author Paul Newman, a research scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "Over areas that are farther from the poles like Africa or the continental U.S., the annually averaged levels of upper atmospheric ozone are only three to six percent below natural levels. But, over Antarctica, ozone is 70 percent lower in the spring. This new method allows us to more accurately estimate ozone-depleting gases over Antarctica, and how they will decrease over time, reducing the ozone hole area." For the first time, a model combines estimates of future Antarctic chlorine and bromine levels based on current amounts as captured from NASA satellite observations, NOAA ground-level observations, NCAR airplane-based observations, with anticipated future emissions, the time it takes for the transport of those emissions into the Antarctic stratosphere, and assessments of future weather patterns over Antarctica. The model accurately reproduces the ozone hole area in the Antarctic stratosphere over the past 27 years. Using the model, the researchers predict that the ozone hole will recover in 2068, not in 2050 as currently believed. International agreements such as the Montreal Protocol, approved in 1987, limit production of ozone-depleting substances. Later changes to those international agreements have completely eliminated legal production of most of these chemicals, though there will be continued emissions of previously produced and stored amounts of those chemicals that are not destroyed or recycled. The researchers also show that the ozone hole has not yet started to significantly shrink, something they predict will not start to occur until 2018. Newman's team also further indicated that greenhouse gas-forced climate change will have only a small impact on the Antarctic stratosphere and recovery of the ozone hole. The upper ozone layer is important because it blocks 90-99 percent of the sun's ultraviolet radiation from making contact with Earth. This solar radiation can cause skin cancer, genetic damage, eye damage and can impact marine life. "My job is to track ozone-depleting chlorofluorocarbons around the globe on a weekly basis," said Steven Montzka, a research chemist in the Global Monitoring Division at NOAA's Earth Systems Research Laboratory in Boulder, and co-author of the paper. "We make calculations with that information to determine how gases containing chlorine and bromine that have life spans in the atmosphere ranging from 45 to about 300 years, are affecting ozone. This new prediction model is a very useful step forward to refining our understanding of ozone hole recovery time scales." The researchers included ozone data from the Total Ozone Mapping Spectrometer (TOMS) on NASA's Earth Probe TOMS satellite, gas measurements from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite, temperature information from NOAA's polar orbiting series satellites, and data captured by NOAA ground stations and weather balloons to create the new prediction model. To view related Antarctic ozone hole images on the Web, visit: http://www.nasa.gov/cente(...)/ozone_recovery.html For more information about the Antarctic ozone hole on the Web, visit: http://ozonewatch.gsfc.nasa.gov/
Drugshond	donderdag 28 december 2006 @ 20:03
	Laatste gegevens. 28-12-2006 Totaal overzicht Noordpool Zuidpool
Drugshond	dinsdag 9 januari 2007 @ 18:26
	Gaat lekker boven Canada/Alaska. - Toch de schaal weer aanpassen ? - O wacht.... hoe kleiner de waarde hoe erger de situatie. quote: Bron : ACE.MMU The ozone layer over Canada is normally thicker in winter and early spring, varying naturally by about 25% between January and July. Weather conditions can also cause considerable daily variations. [ Bericht 67% gewijzigd door Drugshond op 09-01-2007 18:33:58 ]
Rickocum	dinsdag 9 januari 2007 @ 19:26
	Achhh hier valt et nog mee, laat die amerikanen eerst maar genieten van de toenemende huidaandoening gevallen
Grrrrrrrr	dinsdag 9 januari 2007 @ 19:29
	Hmm, en ik dacht juist dat we het ergste wel gehad hadden. Het laatste jaar eigenlijk alleen maar positieve voorspellingen gezien over de laag... Bummer .
pfaf	dinsdag 9 januari 2007 @ 19:38
	quote: Op dinsdag 9 januari 2007 19:29 schreef Grrrrrrrr het volgende: Hmm, en ik dacht juist dat we het ergste wel gehad hadden. Het laatste jaar eigenlijk alleen maar positieve voorspellingen gezien over de laag... Bummer . Inderdaad, ik hoor al een decennium lang dat het gat weer aan het dichtgroeien is...