lunes, 20 de septiembre de 2010

Capa de ozono se mantiene estable


Un nuevo reporte sugiere que los esfuerzos internacionales para parar la destrucción de la capa de ozono han resultado exitosos hasta el momento. El reporte, dado a conocer durante el Día Internacional de la Preservación de la Capa de Ozono de la ONU, provee nueva información sobre los efectos climáticos a nivel global y los efectos que el cambio climático podría tener en la capa de ozono en el futuro.

El Protocolo de Montreal, firmado en 1987, fue el acuerdo mediante el cual los países firmantes se comprometieron proteger la capa de ozono mediante la prohibición del uso de sustancias reductoras del ozono como los clorofluorocarbonos (CFC), los cuales se cree que son los principales responsable de la dramática reducción de la capa de ozono observada el siglo pasado, sobre todo en la Antartida.

De acuerdo al reporte, aparentemente el Protocolo de Montreal está funcionando y ha ayudado a regenerar el ozono estratosférico hasta niveles mucho mayores gracias a la reducción en el consumo de sustancias como los CFC, que anteriormente eran ampliamente usados en sistemas de refrigeración.
Dado que muchas sustancias que dañan la capa de ozono son potentes gases de efecto invernadero, los beneficios obtenidos con el Protocolo de Montreal han sido dos:
  1. Detener la pérdida de la capa de ozono que es necesaria para la vida.
  2. Reducción del efecto invernadero, que ya está teniendo impacto sobre el clima terrestre.
Los datos del reporte afirman que el ozono a nivel global ya no esta decreciendo

The report finds that the global ozone is no longer decreasing though not yet increasing, and that due to the Montreal Protocol the ozone layer outside the polar regions is projected to recover to pre-1980 levels by the mid 21st century, a recovery that may be sped up if greenhouse gases cool the upper stratosphere.

The springtime hole over the Antarctic however is not projected to recover until much later which may or may not be a good thing according to research from University of Leeds which suggests the hole may be preventing further warming. Here UV levels remain high and the effect on surface climate is becoming evident, leading to important changes in surface temperature and wind patterns. At mid-latitudes, surface UV has remained fairly constant over the past decade.

The mixed news continues: while CFCs have been phased out, demand has risen for replacement substances known as HCFCs (hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons) which are also powerful greenhouse gases. These are predicted to decline over the next decade but are currently increasing faster than four years ago, at an overall rate of approximately 8% per year. For example, HFC-23 is a byproduct of HCFC-22 production and has no impact on the ozone layer, but it is more than 14,000 times more powerful as a greenhouse gas than CO2. However, the overall reduction of of ozone-depleting substances has been five times larger than those initially targeted during the commitment period 2008-2012 as set out by the Kyoto Protocol.

The report stressed that climate change will continue to affect the ozone layer despite efforts because of continued emissions of long-lived greenhouse gases, mainly carbon dioxide, associated with human activities.

Achim Steiner, UN Under-Secretary General and United Nations Environment Programme Executive Director said: "This represents a further potential area for action within the overall climate change challenge. An international group of modellers working with UNEP recently concluded that current commitments and pledges linked with the Copenhagen Accord are unlikely to keep a global temperature rise to under 2°C by 2050. The gap between scientific reality and ambition is estimated to average around 4.7 Gigatonnes of CO2 equivalent per year-a gap that needs to be urgently bridged over the next decade or so if the 2°C target is to be met.

"The ozone-hole issue demonstrates the importance of long-term atmospheric monitoring and research, without which ozone destruction would have continued unabated and might not have been detected until more serious damage was evident," said WMO Secretary-General Michel Jarraud. “Without the Montreal Protocol and its associated Vienna Convention atmospheric levels of ozone-depleting substances could have increased tenfold by 2050. This in turn could have led to up to twenty million more cases of skin cancer and one hundred and thirty million more cases of eye cataracts, not to speak of damage to human immune systems, wildlife and agriculture,” added Achim Steiner.

The report, the first comprehensive update in four years, was published by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP). The executive summary of the Scientific Assessment of Ozone Depletion 2010 will be presented by the Scientific Assessment Panel at the next annual Meeting of the Parties to the Montreal Protocol, to be held in Kampala, Uganda, from 8 to 12 November 2010. The full body of the report will be available in early 2011.



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