Hole In Ozone Layer Expected To Make Full Recovery By 2070.


ozone layer recovery 2070

2070 is shaping up to be a great year for Mother Earth.

That’s when NASA scientists are predicting the hole in the ozone layer might finally make a full recovery. Researchers announced their conclusion, in addition to other findings, in a presentation Wednesday during the annual American Geophysical Union meeting in San Francisco.

The team of scientists specifically looked at the chemical composition of the ozone hole, which has shifted in both size and depth since the passing of the Montreal Protocol in 1987. The agreement banned its 197 signatory countries from using chemicals, like chlorofluorocarbons (CFCs), that break down into chlorine in the upper atmosphere and harm the ozone layer.

They found that, while levels of chlorine in the atmosphere have indeed decreased as a result of the protocol, it’s too soon to tie them to a healthier ozone layer.

“Ozone holes with smaller areas and a larger total amount of ozone are not necessarily evidence of recovery attributable to the expected chlorine decline,” Susan Strahan of NASA’s Goddard Space Flight Center explained in a media briefing. “That assumption is like trying to understand what’s wrong with your car’s engine without lifting the hood.”

Instead, the scientists believe the most recent ozone hole changes, including both the largest hole ever, in 2006, and one of the smallest holes, in 2012, are primarily due to weather. Strong winds have the ability to move ozone in large quantities, effectively blocking the hole some years, while failing to block it in others.

“At the moment, it is winds and temperatures that are really controlling how big [the ozone hole] is,” Strahan told the BBC.

LiveScience reports weather is expected to be the predominant factor in the ozone hole’s size until 2025, at which point CFCs will have dropped enough as a result of the Montreal Protocol to become noticeable.

By 2070, however, the ozone hole is expected to have made a full recovery.

“It’s not going to be a smooth ride,” Strahan cautioned the Los Angeles Times. “There will be some bumps in the road, but overall the trend is downward.”

Researchers find tie between global precipitation and global warming.


The rain in Spain may lie mainly on the plain, but the location and intensity of that rain is changing not only in Spain but around the globe.

A new study by Lawrence Livermore National Laboratory scientists shows that observed changes in global (ocean and land) precipitation are directly affected by human activities and cannot be explained by natural variability alone. The research appears in the Nov. 11 online edition of the Proceedings of the National Academy of Sciences.

Emissions of heat-trapping and ozone-depleting gases affect the distribution of precipitation through two mechanisms. Increasing temperatures are expected to make wet regions wetter and dry regions drier (thermodynamic changes); and changes in will push storm tracks and subtropical dry zones toward the poles.

“Both these changes are occurring simultaneously in global precipitation and this behavior cannot be explained by natural variability alone,” said LLNL’s lead author Kate Marvel. “External influences such as the increase in are responsible for the changes.”

The team compared climate model predications with the Global Precipitation Climatology Project’s global observations, which span from 1979-2012, and found that natural variability (such as El Niños and La Niñas) does not account for the changes in global precipitation patterns. While natural fluctuations in climate can lead to either intensification or poleward shifts in precipitation, it is very rare for the two effects to occur together naturally.

“In combination, manmade increases in greenhouse gases and stratospheric ozone depletion are expected to lead to both an intensification and redistribution of global precipitation,” said Céline Bonfils, the other LLNL author. “The fact that we see both of these effects simultaneously in the observations is strong evidence that humans are affecting global precipitation.”

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Marvel and Bonfils identified a fingerprint pattern that characterizes the simultaneous response of precipitation location and intensity to external forcing.

“Most previous work has focused on either thermodynamic or dynamic changes in isolation. By looking at both, we were able to identify a pattern of precipitation change that fits with what is expected from human-caused climate change,” Marvel said.

By focusing on the underlying mechanisms that drive changes in global precipitation and by restricting the analysis to the large scales where there is confidence in the models’ ability to reproduce the current climate, “we have shown that the changes observed in the satellite era are externally forced and likely to be from man,” Bonfils said.

Ozone hole could boost global warming.


The thinning of the atmosphere’s ozone layer could be contributing to warming the planet, according to a study published this week in Geophysical Research Letters.

Kevin Grise, an atmospheric scientist at Columbia University in New York, and his team modelled the weather dynamics around the ozone hole above the Antarctic. They calculated the knock-on effects of ozone depletion on cloud cover, and ultimately on radiative forcing — the balance of solar and thermal radiation absorbed, reflected or emitted by the planet and its atmosphere.

 

Previous research by Piers Forster, an atmospheric scientist at the University of Leeds, UK, and his collaborators attributed a slight cooling effect to the ozone hole. But the latest study, which focused on the Antarctic summer between December and February, found that there may be a warming effect instead.

The team’s models predicted a shift in the southern-hemisphere jet stream — the high-altitude air currents flowing around Antarctica — as a result of ozone depletion. This produced a change in the cloud distribution, with clouds moving towards the South Pole, where they are less effective at reflecting solar radiation.

The result was that the effects on the Earth’s net energy balance were opposite to what had been calculated before. “A negative radiative forcing is what you’d expect when the ozone is depleted, but our research shows that there is a positive net radiative effect during the Antarctic summer,” Grise says.

The extra net energy absorbed by the Earth would be 0.25 watts per square metre, or roughly a tenth of the greenhouse effect attributed to CO2, Grise says. The result could be a small but non-negligible contribution to global temperature rise.

“I think it’s an interesting piece of research. They are talking about a new mechanism in the world of ozone and climate change,” says Forster. “There’s quite a lot of work to be done to pin down the mechanism, but it does sound reasonable.”

Source: Nature

Ozone Hole and The Global Climate Changes.


The release of CFCs or chlorofluorocarbons into the atmosphere through human activities has caused a massive hole in the ozone layer right above Antarctica and if unchecked, melting icecaps may inundate several regions of the earth in the future.

What is Ozone and Where Is It Found in The Earth’s Atmosphere?

Ozone is a gas with a pungent odor whose molecule contains three oxygen atoms. At about 6–10 miles above the Earth’s surface and extending up to 30 miles, in a region of space called the stratosphere, you will find 90% ozone. The stratospheric region with the highest ozone concentration is commonly known as the “ozone layer”. The remaining ozone, about 10%, is found in the troposphere, which is the lowest region of the atmosphere, between Earth’s surface and the stratosphere.

Ozone at ground level in the troposphere is bad because it causes photochemical smog. The smog results when ultra-violet light falls on and reacts with nitrogen oxide from vehicle exhausts. Because of this, Ozone affects lung function, aggravates asthma and other chronic respiratory diseases.

On the other hand, ozone in the stratosphere performs a very useful function by acting as a blanket that blocks most of the sun’s high-frequency ultraviolet rays. These UV rays can cause skin cancer and cataracts in humans, as well as reproductive problems in several forms of life including even the single-celled phytoplankton at the bottom of the ocean food chain.

How Does Ozone Form in the Atmosphere?

When ultraviolet light strikes oxygen molecules containing two oxygen atoms (O2), it splits them into individual oxygen atoms (atomic oxygen), which then combines with unbroken O2 to create ozone, O3. Being unstable, this ozone once again splits into a molecule of O2 and an atom of atomic oxygen under the action of ultraviolet light. This continuing process called the ozone-oxygen cycle.

The ozone layer  is very effective at screening out UV-B; Nevertheless, some UV-B, particularly at its longest wavelengths, reaches the surface. Ozone cannot stop UV-A, the longer wavelength ultraviolet radiation which  reaches the earth’s surface. However, this type of UV radiation is significantly less harmful to DNA.

The thickness of the ozone layer varies widely throughout the world, being smaller near the equator and larger towards the poles. It also varies with season, being in general thicker during the spring and thinner during the autumn in the northern hemisphere.

Ozone ‘Hole’

In May 1985 scientists with the British Antarctic Survey announced the discovery of a huge hole in the ozone layer over Antarctica. They announced that Ozone levels over the northern hemisphere had been dropping by 4% per decade. They described the larger seasonal drops in the ozone levels around the south pole as a ozone hole.

The ozone hole is not technically a “hole” with no ozone is present, but is actually a region of exceptionally depleted ozone in the stratosphere over the Antarctic during the Southern Hemisphere spring (August–October).

Stratospheric temperatures in the Northern Hemisphere during winter/spring are generally slightly warmer than those in the Southern Hemisphere. Therefore ozone losses over the Arctic have been much smaller than over the Antarctic during the 1980s and early 1990s. However, the Arctic stratosphere has gradually cooled over the past few decades, and Ozone holes have been observed at the Arctic regions too recently. This is a dangerous trend, because unlike the Southern Polar hemisphere, the Northern Polar hemisphere is well populated.

Ozone hole is caused by chemicals called CFCs, or chlorofluorocarbons. CFCs escape into the atmosphere from refrigeration and propellant devices and processes. In the lower atmosphere, they are so stable that they persist for decades. Eventually, some of the CFCs reach the stratosphere where chemical reactions take place primarily on the surface of polar stratospheric clouds, ice particles, or liquid droplets, which form at high altitudes in the extreme cold of the polar regions. Ultraviolet light breaks the bond holding chlorine atoms (Cl) to the CFC molecule. Chlorine then destroys ozone molecules by “stealing” their oxygen atoms. The breakdown of ozone in the stratosphere makes it unable to absorb ultraviolet radiation. Consequently, the unabsorbed ultraviolet-B radiation is able to reach the Earth’s surface. The extent of ozone destruction is extremely sensitive to small changes in stratospheric temperature.

Another culprit responsible for the ozone depletion is nitrous oxide (N2O). The major sources of nitrous oxide are industrial processes and combustion engines of various vehicles. They are also emitted from livestock manure and sewage. Like CFCs, Nitrous oxide  is stable when emitted at ground level, but breaks down when it reaches the stratosphere to form nitrogen oxides that trigger ozone-destroying reactions.

In 1987 several UN countries gathered at Montreal, Canada, and signed a treaty to protect the stratospheric ozone layer. The Montreal Protocol stipulated that the production and consumption of compounds that deplete ozone in the stratosphere—chlorofluorocarbons, halons, carbon tetrachloride, and methyl chloroform—are to be phased out by 2005.

Chemical manufacturers soon created substitutes for CFCs with little added costs; thus, our life styles remained greatly unaffected by the switch-over from CFC’s. This has had the effect of putting a slow stopper on the Ozone hole.

Now, the issue of a possible connection between ozone hole and global warming is a controversial subject even among scientists. In fact, there is no unanimity in either of the assertions that Antarctica is warming or cooling. The British Antarctic Survey says categorically Antarctica to be both warming around the edges and cooling at the center at the same time. Thus it is not possible to say whether it is warming or cooling overall. Because there are too many parameters governing the global temperatures, it is difficult to correlate the theoretical temperature rise at the Antarctic caused by a thinner ozone layer with global climatic changes. It is useful to remember here that Ozone itself is a greenhouse gas and its thinning over the region reduces heat trapped over it and helps create sea spray that forms reflective, cooling clouds.

Source: http://scienceray.com