The Atmosphere: Our Planet's Safety Net - Climate Change: The Planet's Pulse

The majority of us probably don't give much thought to Earth's atmosphere, let alone the impact that humans are having on it. All things considered, it's not going anywhere

In the middle of the day, it's hard to make sense of the sky. A mysterious distance exists between us and our atmosphere, but we can feel its allure. The air we breathe is like a pale blue blanket that wraps around Earth and clings to us thanks to gravity. Birds, planes, a constantly shifting pattern of clouds, and in some areas, smog, are all visible. In the distance, we can see the Moon shining brightly and the Sun high in the sky. From Earth, it's difficult to tell where our atmosphere ends and space begins. (Our environment is very complex, like an elaborate cake.)

Then night comes, and a window to the heavens opens in the gloom, illuminating itself only by the glow of the Moon, stars, and beyond. As night falls, it becomes even more difficult to gauge the state of our atmosphere.

The true character of Earth's atmosphere is revealed only when viewed from the vantage point of space. To see our planet from space is to see it in a whole new light. Below us, the limb of Earth's atmosphere glows like a halo of colors; a luminescent layer cake that gradually fades into the blackness of space. Suddenly, the vastness and mystery of our atmosphere, as seen from the ground, appears shockingly thin, even fragile.

As Scott Kelly, a former NASA astronaut, figured: As his yearlong mission aboard the International Space Station was drawing to a close in February 2016, he told CNN, "When you look at the big picture, it's clear that we've made some significant progress." I wouldn't say the atmosphere on Earth's limb is unhealthy, but it does appear to be extremely delicate and almost paper-thin, so it's clear that this is an area that requires special attention. Similar comments by other NASA astronauts have been reported.

Really, we can't take Earth's atmosphere for granted. The web of life as we know it would collapse without it. It shields us from dangerous ultraviolet solar radiation and provides us with the oxygen we need to survive. Liquid water on Earth's surface wouldn't be possible without this pressure being generated. It also keeps Earth's temperature at a level that supports life.

To be more precise, Earth's atmosphere has a mass of only about a millionth of the planet itself, making it extremely tenuous. In addition, the troposphere, the lowest layer of the atmosphere, is only 12 kilometers (7 miles) in average height. thick (as in, over 5 miles)

The accepted standard for the transition from Earth's atmosphere to space is around 100 kilometers (62 miles) above ground level. Driving that far on the ground might allow you to experience a change in scenery. But if you climb that high, you'll soon reach an area that isn't suitable for human habitation. There is not enough oxygen for humans to survive at altitudes above about 8 kilometers (5 miles). Unless you're in a pressurized environment, your blood starts to boil at an altitude of about 19 kilometers (12 miles).

Consequently, how massive an atmosphere does Earth have? Do you think it's going to be fragile or strong? Constant or prone to sudden change? To what extent, exactly, do humans play a role?

It appears that all of the above are correct, and that we have a major impact. This five-part series is the result of an interview with a panel of NASA atmospheric scientists.

A "Radical" Substance Necessary for Atmospheric Stability

First, we must agree on what we mean when we talk about the fragility or stability of Earth's atmosphere. According to Kevin Bowman, a researcher at NASA's Jet Propulsion Laboratory in Pasadena, California, and the man in charge of the TES instrument aboard the Aura satellite, this is the case. Beginning in 2004, TES was in operation until early 2018.

According to Bowman, "the chemistry of Earth's atmosphere is remarkably stable, providing a relatively safe place for animals and plants to thrive." But even slight modifications to the air we breathe can have significant effects on our health, the authors write. The study of atmospheric chemistry focuses on understanding the stability of the atmosphere, how it may be affected by humans, and how it interacts with the rest of the Earth system. ”

According to Bowman, the hydroxyl radical (OH) is a crucial component in the ability of Earth's atmosphere to purge pollutants from the air. OH, one of the most reactive gases, acts as a global detergent, cleaning the air and restoring equilibrium by reducing pollution levels. Carbon monoxide, sulfur dioxide, hydrogen sulfide, methane, and higher hydrocarbons are all primarily controlled by this factor.

Primary production of hydroxyl radicals (OH) as predicted by models, animated over the course of a day in July 2000. Concentration follows the path of the sun around the world. OH recycling in the presence of nitric oxide and nitrogen dioxide, which are common pollutants from cars and industry, is likely to increase OH levels over populated land. Photos by NASA/Julie Nicely

Numerous unanswered questions surround OH among scientists. They are interested in its stability, the rate at which it removes these chemicals from the air, and the ways in which this ability has changed over time and might change in the future. They are also concerned about the impact climate change may have on the security of Ohio. Methane is a potent greenhouse gas, and its continued increase will lead to OH consumption and a decline in air quality.

Atmospheric models using data from satellites, aircraft, and ground measurements are used to forecast future changes in OH's ability to clean the air. The models, according to Bowman's research on ancient climates, "underestimate the sensitivity of OH to climate change." Consequently, "our atmosphere might be more variable than we thought," and "OH might end up changing much more rapidly than predicted," with negative consequences for surface air quality, greenhouse gas concentrations, and ozone levels. ”

Since OH can't be measured directly, determining its concentration has been difficult for scientists, according to Bowman. In the past, researchers estimated OH concentrations by measuring concentrations of methyl chloroform, another trace gas that was widely used as an industrial solvent in the 1950s and was produced by bomb blasts at that time. Methyl chloroform is slowly degraded by OH, the only known reaction it has with. Methyl chloroform was once a reliable method for estimating OH concentrations in the atmosphere, but it has since been superseded by other solvents.

Scientists now have a new tool at their disposal thanks to observations from instruments like TES for estimating OH via "chemical weather forecasts" generated by computer models of the atmosphere. Scientists have improved their representation of OH in these models thanks to TES measurements of ozone, carbon monoxide, and nitrogen dioxide, all of which are influenced by OH. So far, studies using TES data have shown that OH is sensitive to changes in emissions, particularly in the tropics, and that there is more OH in the northern hemisphere than the southern hemisphere, which is consistent with methyl chloroform concentrations.

The relative concentrations of ozone (above) and carbon monoxide (browse view) in the atmosphere were measured in January 2006 by NASA's Tropospheric Emission Spectrometer onboard the Aura satellite. Thanks to NASA

Average global thermal absorption of ozone as measured by NASA's Aura spacecraft's Tropospheric Emission Spectrometer instrument in August 2015, with contributions from nitrogen dioxide emissions (the primary source of ozone). 2006 A high value (in red) indicates that emissions there contribute more than average to the trapping of heat in the Earth's atmosphere. NASA-JPL/Caltech/CU-Boulder are to be credited for this.

Bowman elaborated on the many other scientific breakthroughs made possible by TES. Largely, it has helped us better understand ozone in the troposphere. Our knowledge of how ozone impacts human health, climate, and other parts of the Earth system has been greatly enhanced by the data collected by TES and the other instruments on board Aura. A study published in 2015 by TES demonstrated how ozone emitted in the United States was increased by ozone transported from Asia. S Coast, even though the US S decreases in ozone emissions How much ozone in the upper troposphere acts as a greenhouse gas, warming the atmosphere, was also measured with the help of TES data. The data was used to assess the veracity of climate models' projections of ozone's greenhouse effect and to put a number on the impact that regional shifts in ozone-causing pollutants have had on the planet's weather. Increases in tropospheric ozone levels have been documented by TES measurements in many regions around the world, including Asia, adding to our knowledge of global air quality.

Data from NASA's Aura spacecraft is used to estimate the monthly mean maximum daily average background ozone concentration in parts per billion over California and Nevada. NASA/JPL-Caltech/George Mason University

The emissions of pollutants that form ozone are being redistributed, Bowman said. "As they move toward the equator, ozone will become a more powerful greenhouse gas." ”

By measuring so-called "heavy" water molecules, a naturally occurring variant of water that contains more neutrons than normal water molecules and provide clues to how the water evaporating and falling as precipitation in the past, TES, according to Bowman, has also provided a window into Earth's water cycle. To that end, this information is useful for elucidating atmospheric water vapor control mechanisms. The data were used in a study that revealed how the Amazon triggers its own rainy season.

In addition, TES gave researchers fresh data on the precursor to harmful aerosols, ammonia; and on the carbon cycle, thanks to new measurements of carbon-containing gases like methane and carbonyl sulfide.

Bowman remarked, "TES was a pioneer." As the author puts it, "It collected a completely new set of measurements using new techniques that are now being used by a new generation of instruments." ”

Visit https://tes.jpl.nasa.gov/ for more information about TES.

Our next topic will be "The Atmosphere: Controlling Carbon Dioxide."