CHAPTER 2: OUR CHANGING ATMOSPHERE:
WARMING AIR, WARMING PLANET
The air we breathe
Life on Earth would not be possible without our air.
Our air (the atmosphere) provides us with oxygen to breathe and carbon dioxide for plants to live. But the atmosphere does a lot more than provide air for living organisms. The atmosphere also helps to regulate Earth’s temperature. This means that the air helps to keep temperatures not too hot and not too cold, but just right so that it can support life. The Earth has an average global temperature of about 15°C (59° F).
Every day, sunlight (the sun’s radiation) travels through the atmosphere and warms the planet. The atmosphere helps to trap this warmth on Earth – if you remember from the introduction, this process is called the greenhouse effect. The atmosphere protects us from the Sun’s powerful rays, like a natural form of sunscreen. Without the atmosphere, our planet would essentially be freezing cold at night, and scorching hot during the day. No air on Earth means it would be a lot like the moon – hotter than boiling water during the day (126.7°C or 260°F) and more than twice as cold as any place on Earth at night (-173°C or -280°F), and without any life, completely barren.
Although we can’t see everything in the atmosphere with our naked eye, it contains many different gases. About 99.998% of the air is composed of five main gases: nitrogen (~78%), oxygen (~20%), argon (~0.9%), water vapor (~1-3%), and other gases, including carbon dioxide (~0.03%). All of these gases – and many others that are in the air but in much smaller quantities – are essential for life. Some gases in the air are heat-trapping gases, called greenhouse gases. The major greenhouse gases in our air are carbon dioxide, methane, nitrous oxide and water vapor. There are also other greenhouse gases in smaller amounts, such as CFC's (chlorofluorocarbons), HFCs (hydrofluorocarbons) and PFC's (perfluorocarbons). These are synthetic chemicals that are emitted from human activities like manufacturing and refrigeration. So what happens when we put more greenhouse gases in the air? It warms! Greenhouse gases help to keep the planet warm, but when they build up in the atmosphere, they have a big impact on how much heat remains in the air.
While we understand that the greenhouse effect is a natural process that allows us to live on Earth, we've also learned that human activities have introduced a lot more greenhouse gases in recent years that are raising the temperature of our air and having a big impact on climate change. Therefore, humans are changing the natural greenhouse of Earth.
Let’s take a closer look at the greenhouse effect in this video. We see how solar radiation passes through the atmosphere and heats up Earth’s surface. Some of the radiation is absorbed by gases even before it reaches the land and ocean surfaces. The other part is absorbed by the Earth’s surface and then radiated upward. As the gases in the air absorb both the Sun’s and the Earth’s energy, they warm up and also radiate heat.
LAYERS OF THE ATMOSPHERE
The five major layers of the atmosphere are the troposphere, stratosphere, mesosphere, thermosphere and exosphere. Each layer of the atmosphere has a different concentration of gases and different temperatures.
Almost all the weather occurs in the troposphere, since this is where the majority of water vapor and dust particles are found. Most of the clouds we see overhead are part of the troposphere. The temperature of the troposphere is particularly relevant to climate change because the majority of warming in this layer is due to greenhouse gases trapping heat and Earth’s radiation.
The stratosphere, just above the troposphere, is dry, not very dense, and essentially cloud-free. This layer has a lot of ozone, a gas that makes up the ozone layer and absorbs a great deal of the Sun’s incoming radiation. The air temperature increases with altitude in the stratosphere. Weather balloons fly in this layer. Commercial jet aircrafts tend to fly just below this layer, where there are a lot less clouds and less turbulence.
The mesosphere is where most meteors burn up upon entry into Earth’s atmosphere. Temperature in this layer decreases with increasing altitude. The coldest place on Earth is in the upper mesosphere! The highest portion of this layer has temperatures of -90°C (-130°F).
The thermosphere has very thin air, and the temperature is very sensitive to solar activity and can become very hot during the day, rising up to 2,482°C (4,500°F) in the upper thermosphere! The International Space Station orbits in the thermosphere. The northern lights, or aurora borealis, occur in the thermosphere.
The exosphere is the uppermost region of the Earth’s atmosphere. It is the very thinnest layer of all and gradually fades into outer space.
Carbon dioxide—the main greenhouse gas
One of the most important gases in our air is carbon dioxide (CO2). CO2 is a molecule that is made up of one carbon atom and two oxygen atoms. CO2 is a greenhouse gas that traps heat.
When we think about the amount of warming in the air, we consider how much of a particular gas is in the air (abundance), how long it stays in the air (residence time), and how much heat it can trap (heat trapping ability). These three variables influence the global warming potential of a greenhouse gas.
Water vapor is great at trapping heat, but typically only stays in the air for only a few days. Just think of those super-humid days in the southern United States during the summer — luckily, it changes fast and the temperatures cool immediately after a summer rain. On the other hand, CO2 released into the air today will stay in the air for generations to come. Carbon dioxide can stay in the air for a few hundred years! There are other gases in the air that can absorb even more heat than CO2, like nitrous oxide (N2O) and methane (CH4), but CO2 is important because there is a lot of it in the air due to human activities and concentrations keep rising. Methane, made of one carbon and four hydrogen atoms, is also an important greenhouse gas because it can trap a lot more heat than carbon dioxide, though it stays in the air for a shorter time period, about 12 years.
CO2 plays a major role in the basic functioning of all living things. Plants need CO2 to turn sunlight into food and produce oxygen in photosynthesis. Animals and humans breathe in oxygen, and breathe out CO2 and water vapor during respiration.
The amount of carbon dioxide in the air changes throughout the year corresponding to the growing season of plants. In the summer, plants in the Northern Hemisphere absorb a great deal of CO2 because that is the season when they grow the most. Take a look at this video to see the Earth’s respiration and cycling of CO2 throughout the year. You will see how CO2 in the air increases during the winter, but decreases in the spring and summer months when plants take in CO2 in plant respiration.
Scientist Charles Keeling was the first scientist to make consistent measurements of carbon dioxide concentrations in the air. He began his measurements in 1958 at the Mauna Loa Observatory, in Hawaii. He was the first scientist to alert the world to anthropogenic – human-caused – contributions to the greenhouse effect. The graph that shows the changes in CO2 in the air is named after him – it is called the Keeling Curve. In this graph, we can see the annual rise and fall of CO2 due to plant respiration, and the overall measurements show that the concentration of CO2 in the air keeps rising. In 1958, when Keeling first started to record concentrations, there were about 315 parts CO2 per million of CO2 in the air. Today, carbon dioxide in the air measures over 400 ppm! NASA scientists have found that we are contributing an average of 2 ppm of CO2 each year, and that we need to lower this concentration to a more sustainable level in order to help keep the Earth in balance. A target of 350 ppm of CO2 or less is recommended, and we can all do something to help reduce current concentrations.
- In the Keeling Curve, the measurements of CO2 in the air are represented by ppmv, which stands for “parts per million volume."
- Parts per million volume is commonly used in climate science to describe how much gas is in the air – it is the ratio of a volume of a given gas mixed in a million volumes of air.
- One ppmv means that there is 1 part in 1,000,000 parts (or 0.0001%). The higher the number, the more gas there is in the air.
- A gas is one of the three common states of matter (solid, liquid and gas).
- The atmosphere around our Earth is one big layer of gas. Gases, just like all other matter in the universe, are made of clusters of atoms. Any two atoms joined together is called a molecule.
- An element is a pure substance that is made from one single type of atom. Some of the most common basic elements of gases in the air are hydrogen (H), carbon (C), oxygen (O) and nitrogen (N).
- Throughout the history of Earth, CO2 concentrations in the air have fluctuated. Various factors during different eras have produced natural rises and falls in the amount of CO2 in the atmosphere. When human civilization began, there was less than 300 ppmv of CO2 in the air, and today there is over 400 ppmv.
- Our air hasn’t had more than 400 ppm of CO2 in over two million years. Back then the Earth was much warmer (~+5-6 degrees F) and sea level was many feet higher (~+15-20 ft.) than today.
The carbon cycle
Carbon is continuously moving through all parts of the Earth’s ecosystems. It travels through the water, air, plants and animals, and is even found in rocks and soils. To move through the environment, carbon takes several forms, like carbon dioxide in the atmosphere, sugars or carbohydrates in plants and animals, and calcium carbonate in rocks and minerals. This exchange of carbon between all organisms and parts of the Earth is known as the carbon cycle.
When plants take in CO2, what happens to this gas? Plants use solar energy to turn carbon dioxide and water into sugar for energy – the CO2 is removed from the air, and the carbon is used to build tissue and becomes a building block for life. This process is called photosynthesis.
When a plant or animal dies, the carbon it stores returns to the air upon decay or burning. If the plant or animal is buried before it fully decays, then the carbon may be stored for many more years. Peat is plant material that has become waterlogged and buried before it fully decays, and by preserving organic material and storing CO2, it becomes a carbon sink. After millions of years, this peat turns to coal. When the coal is extracted and burned, all of the stored gases return to the air.
CARBON ON EARTH AND VENUS!
Deep inside the Earth’s crust, there is a lot of carbon stored. When there is a volcanic eruption, a large amount of carbon dioxide is released. Venus has many volcanoes and is very close to the sun with a lot of incoming solar radiation. Since it has no oceans or plants there to help absorb and cycle the CO2, the planet has a big greenhouse gas effect that keeps it very hot, with an average temperature of 462°C (864°F).
- Each person exhales about 1 kilogram per day, depending on a person¹s daily activities. There are about 7 billion humans on Earth today, and that means all humans collectively breathe out about 2000 pounds (almost 1 metric ton) of carbon dioxide each day.
- Plants are also busy taking in carbon dioxide for photosynthesis. Each of us is a part of the carbon cycle.
CARBON IS EVERYWHERE!
You may not realize it, but carbon is a part of all kinds of things in our world. Carbon has the chemical element C and the atomic number 6. Carbon bonds well with lots of other elements, which makes it a common building block of life. Three common forms of carbon are coal, diamond, and graphite. What else has carbon? Your pencil has carbon in it – graphite is combined with clay to make the lead in pencils. Plants have about 45% carbon in them. Guess what else is made of carbon — you are! A person who weighs 45.4 kilograms (100 pounds) is about 18% carbon.
CO2, fossil fuels and humans
We know that CO2 in the air is on the rise, and that this is contributing to climate change, but how did we get all of that CO2 in the air? Part of it is naturally occurring, but a lot of it is due to human activity.
Plant and animals that have died over millions of years are buried and become fossils. Some fossil beds in the Earth are very rich in carbon and over time are converted to fossil fuels — oil, coal, and natural gas. Fossil fuels can be extracted from deep in the Earth through drilling and digging, to be used for energy.
During the Industrial Revolution, fossil fuel extraction and use became the primary means of getting energy for manufacturing and transportation. Before that, people typically used timber as the main fuel for heating and cooking, and nobody had invented cars and trains for transportation yet. Today, coal, oil, and gas are used every day to power our modern lives, providing electricity, power, fuel, and heat.
When fossil fuels are burned, they release the ancient carbon that has been stored over millions of years as carbon dioxide back into the atmosphere. Of course, the fossil fuels are being used much more quickly than they form. We see an increase in CO2 because we are rapidly adding to the greenhouse effect of our planet. Other types of human activities that add CO2 into the air include burning tropical forests for agriculture or ranching, or draining peatlands for agriculture, forestry or peat extraction.
When CO2 is released into the atmosphere, the plants living today can take in some of it, but a lot of it stays in the air. About half of the CO2 released by fossil-fuel burning stays in our air. Approximately one-quarter (25%) is absorbed by the ocean and used by marine plankton. Plants on the land absorb another quarter of the CO2 from fossil fuels. If not taken up by the Earth and its organisms, then the CO2 that remains in the air can stay there for a very long time, trapping heat and warming the planet.
Take a look at this video to see “black” carbon circulating around the globe. Black carbon is commonly called soot, which is made of carbon particles resulting from the incomplete combustion of fossil fuels and biofuels. Coal burning and tree burning generate black carbon. Black carbon is the strongest sunlight-absorbing atmospheric particle and significantly warms the air. It also travels long distances, staying in the air for days to weeks.
CARBON SOURCE AND CARBON SINK — WHAT'S THE DIFFERENCE?
All over our planet, various parts of the environment act as carbon sources or sinks. A carbon source produces more carbon than it takes in. Carbon sinks take in more carbon than they produce. Human activities, including all of our fossil-fuel burning, are major carbon sources because we produce much more carbon than we take in. Other carbon sources are fires and the decomposition of plants and animals. The main carbon sinks on earth include the ocean, soil, and plants. Those deep deposits of fossil fuels that have not yet been dug up and burned are also a carbon sink. Carbon sinks take in carbon and hold on to it for long periods of time through physical and biological processes.
- Our atmosphere that regulates our global temperature, protects us from the Sun's radiation, and provides us with oxygen to breathe and carbon dioxide for plants to live.
- Our air is made up of nitrogen (78%), oxygen (20%), argon (0.9%) and greenhouse gases that trap heat and cause a rise in global temperature. Major greenhouse gases include carbon dioxide, methane, nitrous oxide, water vapor, and flourinated gases.
- The burning of fossil fuels (coal, natural gas, and oil) from human activities release large amounts of CO2 that disrupt the natural carbon cycle and change the composition of our air.
- The ocean, plants, and soils are important carbon sinks.
- The Keeling Curve shows the increase of carbon dioxide in parts per million. Today, there is over 400 ppm of carbon dioxide our the air. The CO2 that is emitted today will continue to warm the planet for many years to centuries.
Collapsing Coastal Shores
Immense areas of permafrost extend throughout the Arctic. They are frozen ice and soils that have developed over thousands of years. These areas are important because they are carbon sinks that store greenhouse gases, but when they thaw or are lost to erosion, carbon and methane is released back into the atmosphere. Today, the coast of the Arctic is rapidly eroding, and the permafrost shores are collapsing into the ocean.
One summer, EIS team member Adam LeWinter traveled with Dr. Irina Overeem, from the Institute of Arctic and Alpine Research (INSTAAR), to set up cameras to capture just how quickly the coast is eroding. The time-lapse photographs help to identify some of the local processes that are influencing the crumbling shores.
The team traveled to the remote research area of Drew Point, Alaska, along the Beaufort Sea. The North Slope of Alaska is an isolated tundra wilderness area, dotted by marshy lakes. Setting up camp at the nearby research station, Inigok, the scientists had to put up a bear fence to keep out grizzlies, wolves and other predators searching for food. Even cables and equipment have to be protected from the curious animal visitors. Flying in a helicopter above the camp and scouting for an ideal camera site, the team saw an enormous mammoth tusk coming out of the melting permafrost, likely from the last ice age, tens of thousands of years ago.
Once they arrived at the shore, setting up cameras was a huge challenge. The researchers wanted to capture a view not only from the coast but also from the water, so they could actually see the interaction between the seawater and the permafrost coast. Going out into the water, they wore dry suits to keep warm and dry. It was a challenging juggling act to get the equipment anchored and not soaking wet! See the time-lapse on this very unique camera installation in the coastal seawater.
The coastal permafrost bluffs are breaking off in large chunks, contributing to a loss of 15 meters (49 feet) of shoreline per year in this region. On a seasonal basis, the upper permafrost melts in the summer and re-freezes in the winter, but this "active" layer is only 35 centimeters (13 inches) deep. A stronger melting force is the contact with warm seawater, which comes in strong waves that lap against the coast and undercut the bluffs. This also occurs when the water levels rise due to storm activity. Sea ice typically protects the coastal shoreline, but there has been less and less sea ice each year.
In the past three decades, Arctic temperatures have increased more than the global average, sea surface temperatures have increased, and sea ice has declined. Offshore winds help push the diminishing sea ice away from the coast. Without the protection of the sea ice, the shoreline becomes extremely vulnerable to the erosive forces of strong waves and seasonal storms. The permafrost shoreline is bathed in warming seawater and rapid melting occurs.
In the time-lapse video you can see how the exposed shoreline is affected by a passing storm that brings up the water level, and the ice begins to melt during contact. Eventually the permafrost collapses into the sea. This loss of Arctic coastline is one of the most rapid landscape changes occurring on our planet.
During his trip, Adam felt as if he was at the edge of the world, watching it fall away into the ocean. The time-lapse cameras captured not only the coasts eroding, but also polar bears walking and sleeping near the shore. This is their home, too, that is falling away into the sea.
Less than a month after the cameras were installed, a helicopter pilot saw that the entire shore was on the verge of collapse, and he had to quickly retrieve all the equipment. While the work is certainly challenging, scientists are continuously working hard to monitor these areas and the ways in which climate change is rapidly changing our planet.