NASA: Big ozone holes to go extinct by 2040
Though a new research, NASA has revealed that the next decades will see ozone holes getting smaller and smaller and by 2040, they will all become smaller than 8 million square miles.
The research carried out by scientists at NASA Goddard Space Flight Center looks into the variability of inorganic chlorine in the Antarctic vortex and its implications for ozone recovery.
Ozone-depleting chemicals in the atmosphere cause an ozone hole to form over Antarctica during the winter months in the Southern Hemisphere. Since the Montreal Protocol agreement in 1987, emissions have been regulated and chemical levels have been declining. However, the ozone hole has still remained bigger than 8 million square miles since the early 1990s, with exact sizes varying from year to year.
The size of the ozone hole varies due to both temperature and levels of ozone-depleting chemicals in the atmosphere. In order to get a more accurate picture of the future size of the ozone hole, scientists used NASA’s AURA satellite to determine how much the levels of these chemicals in the atmosphere varied each year.
With this new knowledge, scientists can confidently say that the ozone hole will be consistently smaller than 8 million square miles by the year 2040. Scientists will continue to use satellites to monitor the recovery of the ozone hole and they hope to see its full recovery before the end of the century.
For the research, scientists inferred the interannual variability of inorganic chlorine in the Antarctic lower stratospheric vortex using 9?years of Aura Microwave Limb Sounder (MLS) nitrous oxide (N2O) measurements and a previously measured compact correlation.
Inorganic chlorine (Cly) is the sum of the destruction products of long-lived chlorine-containing source gases. Its correlation with N2O, derived from observations in the year 2000, is scaled to the years 2004–2012 to account for subsequent N2O growth and chlorofluorocarbon decline. The expected annual Cly change due to the Montreal Protocol is ?20?ppt/yr, but the MLS-inferred Cly varies year-to-year from ?200 to +150?ppt.
Because of this large variability, attributing Antarctic ozone recovery to a statistically significant chlorine trend requires 10?years of chlorine decline.
Researchers examined the relationship between equivalent effective stratospheric chlorine (EESC) and ozone hole area. Temperature variations driven by dynamics are a primary contributor to area variability, but researchers found a clear linear relationship between EESC and area during years when Antarctic collar temperatures are 1? or more below the mean.
This relationship suggests that smaller ozone hole areas in recent cold years 2008 and 2011 are responding to decreased chlorine loading. Using ozone hole areas from 1979 to 2013, the projected EESC decline, and the inferred interannual Cly variability, researchers expect ozone hole areas greater than 20 million km2 will occur during very cold years until 2040. After that time, all ozone hole areas are likely to be below that size due to reduced EESC levels.