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January 17, 2020

Earth's atmosphere has a series of layers, each with its own specific traits. Moving upward from ground level, these layers are named the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The exosphere gradually fades away into the realm of interplanetary space.

Troposphere
The troposphere is the lowest layer of our atmosphere. Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level. We humans live in the troposphere, and nearly all weather occurs in this lowest layer. Most clouds appear here, mainly because 99% of the water vapor in the atmosphere is found in the troposphere. Air pressure drops, and temperatures get colder, as you climb higher in the troposphere.
Stratosphere
The next layer up is called the stratosphere. The stratosphere extends from the top of the troposphere to about 50 km (31 miles) above the ground. The infamous ozone layer is found within the stratosphere. Ozone molecules in this layer absorb high-energy ultraviolet (UV) light from the Sun, converting the UV energy into heat. Unlike the troposphere, the stratosphere actually gets warmer the higher you go! That trend of rising temperatures with altitude means that air in the stratosphere lacks the turbulence and updrafts of the troposphere beneath. Commercial passenger jets fly in the lower stratosphere, partly because this less-turbulent layer provides a smoother ride. The jet stream flows near the border between the troposphere and the stratosphere.
Mesosphere
Above the stratosphere is the mesosphere. It extends upward to a height of about 85 km (53 miles) above our planet. Most meteors burn up in the mesosphere. Unlike the stratosphere, temperatures once again grow colder as you rise up through the mesosphere. The coldest temperatures in Earth's atmosphere, about -90° C (-130° F), are found near the top of this layer. The air in the mesosphere is far too thin to breathe; air pressure at the bottom of the layer is well below 1% of the pressure at sea level, and continues dropping as you go higher.
Thermosphere
The layer of very rare air above the mesosphere is called the thermosphere. High-energy X-rays and UV radiation from the Sun are absorbed in the thermosphere, raising its temperature to hundreds or at times thousands of degrees. However, the air in this layer is so thin that it would feel freezing cold to us! In many ways, the thermosphere is more like outer space than a part of the atmosphere. Many satellites actually orbit Earth within the thermosphere! Variations in the amount of energy coming from the Sun exert a powerful influence on both the height of the top of this layer and the temperature within it. Because of this, the top of the thermosphere can be found anywhere between 500 and 1,000 km (311 to 621 miles) above the ground. Temperatures in the upper thermosphere can range from about 500° C (932° F) to 2,000° C (3,632° F) or higher. The aurora, the Northern Lights and Southern Lights, occur in the thermosphere.
Exosphere
Although some experts consider the thermosphere to be the uppermost layer of our atmosphere, others consider the exosphere to be the actual "final frontier" of Earth's gaseous envelope. As you might imagine, the "air" in the exosphere is very, very, very thin, making this layer even more space-like than the thermosphere. In fact, air in the exosphere is constantly - though very gradually - "leaking" out of Earth's atmosphere into outer space. There is no clear-cut upper boundary where the exosphere finally fades away into space. Different definitions place the top of the exosphere somewhere between 100,000 km (62,000 miles) and 190,000 km (120,000 miles) above the surface of Earth. The latter value is about halfway to the Moon!
Ionosphere
The ionosphere is not a distinct layer like the others mentioned above. Instead, the ionosphere is a series of regions in parts of the mesosphere and thermosphere where high-energy radiation from the Sun has knocked electrons loose from their parent atoms and molecules. The electrically charged atoms and molecules that are formed in this way are called ions, giving the ionosphere its name and endowing this region with some special properties.


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October 29, 2016
Earth_experiences_an_ice_age_every_100,000_years

Earth is in a pretty unique state of climate change at the moment, but for the past 1 million years, almost like clockwork, our planet has moved in and out of an ice age every 100,000 years.
The only problem is, researchers have never really been able to figure out why. In fact, they've been so puzzled by the mysterious phenomenon, they've labelled it the '100,000 year problem'. But now a new study might finally have the solution.
New research suggests that our oceans might regularly suck more CO2 out of the atmosphere every 100,000 years, allowing the planet to get cold enough to trigger an ice age.
The '100,000 year problem' stems from the fact that around 1 million years ago, Earth started experiencing ice ages - vast ice sheets covering North America, Europe, and Asia - every 100,000 years.
Before this point, which is known the mid-Pleistocene transition, our planet's ice ages used to occur at intervals of every 40,000 years, which made a lot more sense to scientists.
That's because Earth's angular tilt also wobbles in a 40,000 year cycle, which means every 40,000 years, the planet experiences colder than usual summer months because of the way it's tilted towards the Sun.
That variation in Earth's tilt made the 40,000 year ice ages make sense - but, until now, no one has been able to explain what happened at the mid-Pleistocene transition to overhaul this natural cycle and put our Earth on a 100,000-year schedule instead.
Now researchers have stumbled on a new planetary cycle, and suggest the shift could be a result of our oceans regularly sucking more CO2 out of the atmosphere.
"We can think of the oceans as inhaling and exhaling carbon dioxide, so when the ice sheets are larger, the oceans have inhaled carbon dioxide from the atmosphere, making the planet colder," explains lead researcher Carrie Lear from Cardiff University in Wales.
"When the ice sheets are small, the oceans have exhaled carbon dioxide, so there is more in the atmosphere which makes the planet warmer."
It's long been known that our ocean can store carbon, partly through the action of marine algae, which needs to suck up carbon in order to photosynthesise.
To figure out what was going on, the team looked at the fossilised remains of marine algae over the past millennia to see if the rate at which they sucked up CO2 was constant.
They found that there are periods where the algae showed signs of having sucked up significantly more CO2, and, yep, those periods occurred every 100,000 years or so, corresponding with the timing of Earth's ice ages.
The team suggests that the extra CO2 the marine algae was removing from the atmosphere lowered the temperature long enough for large ice sheets to form in the Northern Hemisphere.
After a while, the CO2 would have been naturally released to the surface through a process known as upwelling, but by that point, the ice age would have been in full swing, and the CO2 would have been trapped in the oceans by a layer of ice across most of the planet, keeping Earth colder for longer.
"If we think of the oceans inhaling and exhaling carbon dioxide, the presence of vast amounts of ice is like a giant gobstopper," said Lear. "It's like a lid on the surface of the ocean."
More research is needed to figure out what makes these marine algae suddenly suck up more CO2 every 100,000 years, and additional study will need to verify that this action is enough to trigger an ice age.
But the study provides useful insight into the cycles that affect our planet, and will continue to affect it in the future.
Right now, Earth is in a warm spell between ice ages, with the last ice age ending about 11,000 years ago.
But there's evidence that human-made climate change has already suppressed the next ice age from happening, and experts don't predict that an ice age will be able to occur for at least another 100,000 years - slightly behind schedule.
Hopefully before then, humanity will have found our own way to curb - and even reduce - the amount of CO2 we're pumping out into the atmosphere, so Earth's natural cycles can have a shot at restoring some of the imbalance in our currently climate system.


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July 02, 2016
earth-outer-layer-or-atmosphere-above-antarctica-is-healing-by-itself
Scientists have found evidence that the hole in the ozone layer over Antarctica is finally beginning to heal. If progress continues, it should be closed permanently by 2050.
The news comes almost 30 years since the world worked together to phase out ozone-depleting chemicals, so we're allowed to give ourselves a little pat on the back. "We can now be confident that the things we’ve done have put the planet on a path to heal," said lead researcher Susan Solomon from MIT.
In the '80s and '90s, the hole in the ozone layer was the environmental threat that everyone was worried about. After decades of pumpingchlorofluorocarbons (CFCs) into the atmosphere - through dry cleaning, aerosols, and old refrigerators - scientists found that the ozone over Antarctica had become seriously thin.
That's not great, seeing as the ozone layer is the shield that absorbs much of the Sun's harmful UV rays before they reach Earth.
To combat the problem, most countries on the planet signed the Montreal Protocol in 1987, which was a global treaty that governed the gradual phase-out of CFCs and other ozone-damaging chemicals.
And now researchers using new longitudinal measurements have shown that the hole is finally starting to heal, and has shrunk by 4 million square kilometres since its peak in 2000. That's roughly half the size of the mainland US.
It did expand to a record size in 2015 due to the eruption of the Chilean volcano, Calbuco, but if environmental progress continues, the hole should be fully closed by mid-century.
"Which is pretty good for us, isn’t it?" said Solomon. "Aren’t we amazing humans, that we did something that created a situation that we decided collectively, as a world, 'Let’s get rid of these molecules'? We got rid of them, and now we’re seeing the planet respond."
Since scientists first started noticing that the ozone hole was getting bigger inthe mid-1980s, they've been monitoring ozone levels every year in October, when moves out of its long winter months and gets sunnier - because chlorine only eats away at ozone when light and cold winds are present.
But the ozone hole starts opening up in August, and Solomon and her team thought they might get more accurate measurements if they tested levels in September, when the temperatures are still cold.
The team was able to show that as chlorine levels in the atmosphere decreased, the rate at which the ozone hole opens up has slowed.
"I think people, myself included, had been too focused on October, because that’s when the ozone hole is enormous, in its full glory," said Solomon. "But October is also subject to the slings and arrows of other things that vary, like slight changes in meteorology. September is a better time to look because chlorine chemistry is firmly in control of the rate at which the hole forms at that time of year. that point hasn’t really been made strongly in the past."
In addition to monitoring the September ozone levels from 2000 to 2015, the team measured the amount of sulphur dioxide emitted by volcanoes each year, which can add to ozone deterioration. They also compared their results with model simulations that predict ozone levels based on the amount of chlorine in the atmosphere each year.
They found that not only did their observations show that the hole was shrinking, it also matched the model's predictions, suggesting that more than half of the change had been driven by the decreasing chlorine in the atmosphere.
"It showed we can actually see a chemical fingerprint, which is sensitive to the levels of chlorine, finally emerging as a sign of recovery," said one of the researchers, Diane Ivy.
The research, which has been published in Science, also shows that we can actually fix some of the damage we've done to the environment when we work together.

"This is a reminder that when the world gets together, we really can solve environmental problems," Solomon told Gizmodo. "I think we should all congratulate ourselves on a job well done."
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