This section of Healing Earth helps you to begin answering the following set of questions posed at the end of the case study:

  • What is global climate change and how has it come about?
  • What are the impacts of global climate change?

Closer Look

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Visit the U. S. National Aeronautics and Space Administration (NASA) webpage and learn more about the difference between weather and climate.

Climate, Weather, and Atmosphere

The terms “weather” and “climate” are sometimes used interchangeably, but there are important differences between them.

Weather refers to the day-to-day changes in the atmosphere on a local basis. Weather is made up of a combination of factors, such as temperature, humidity, cloud cover, precipitation, and wind. Alternately, climate describes the average, as well as the extremes in weather conditions in a regional location over long periods of time. Changes in climate over long periods of time are detected by climatologists, who study patterns in weather and identify long-term trends.

Earth's Atmosphere

Looking Ahead

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You will learn in the upcoming Global Climate Change and Spirituality section that in some religions the air we breathe is a spiritual symbol of the breath of God.

Weather and climate take place in Earth’s atmosphere, which is the thin layer of gases surrounding Earth that is held in place by Earth’s gravity. Without the atmosphere, life on Earth could not exist. It contains the oxygen we breathe, helps warm the Earth, shields us from the sun’s harmful ultraviolet radiation (UV), and is a vital part of the water cycle as was discussed in the Water Chapter.

The atmosphere is made up of a mixture of different gases, minute water droplets, and tiny suspended solid particles (see Table 1). Some of these components are considered permanent components, while others are variable. Permanent components, such as nitrogen and oxygen, are characterized by their stable and consistent presence in the atmosphere at any given time. However, the presence and amount of variable components, such as water vapor, can fluctuate depending on different factors that will be further discussed below.

components of air
Table 1: Composition of Earth’s atmosphere. 1

Compared with the radius of Earth, the depth or thickness of Earth’s atmosphere is very thin. More than 99% of the gaseous molecules (by mass) which make up the Earth’s atmosphere are found in the 50 kilometer thick layer closest to the surface of the Earth (see Figure 1).

layers of earth's atmosphere
Figure 1: The Earth’s atmosphere is a relatively thin and fragile layer of gases- a. an artist’s depiction, b. a satellite image: the thin blue band of gas seen here hovering above the surface of the earth is our fragile atmosphere. Within this band, which is only 50km thick, occur 99.8% of the molecules of gas that support and protect all forms of live on earth. 2

Looking Ahead

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You will learn in the upcoming Global Climate Change and Ethics section that Earth’s atmosphere has intrinsic value. Here, you see the reason why: a healthy atmosphere is necessary for all life on Earth.

The two most abundant gases in the Earth’s atmosphere are nitrogen (N2), which makes up 78% of the volume of the atmosphere, and oxygen (O2), which makes up 21%. Although nitrogen and oxygen together with the other permanent gases account for nearly the entire atmosphere (>99%), and are crucial for life on Earth, they have little to no impact on weather and climate. It is the scarce variable components, like water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) that influence weather and climate.

greenhouse
Figure 2. A greenhouse is made of glass or plastic windows. Sunlight passes through the windows but heat is trapped inside. Vegetables and flowers can grow even during colder months. 3

Water vapor is the most abundant of the atmosphere’s variable components. Its concentration changes from time to time and from place to place. On average, water vapor comprises 0.25% of the atmosphere. As discussed in the Water Chapter, the hydrologic cycle forms clouds from water vapor and produces precipitation that replenishes water in soils, lakes, and rivers. This condensation process (the cooling of water vapor to form liquid water) also releases stored heat, which plays an important role in the development of storms. In these ways, water vapor plays a critical role in weather.

Other gases among the atmosphere’s variable components are present in very small amounts, yet can have a powerful influence on weather. In some cases these trace variable gases are also extremely important to life on Earth.

Looking Ahead

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In the Global Climate Change and Spirituality section you will learn that spiritual traditions such as Hinduism and Islam believe that the interdependent relationship between the atmosphere, plants, animals, water, and soil is a sacred balance.

For example, ozone, which naturally occurs in the stratosphere (10-50 km altitude in the atmosphere) screens out the sun’s ultraviolet radiation (UV) which would otherwise reach the Earth’s surface at levels damaging to living organisms. The screening of UV radiation occurs at very low concentrations of ozone (0.000004%). Ozone is also one of the greenhouse gases (GHGs), and has a strong influence on global warming.

Similarly, carbon dioxide makes up only 0.04% of the atmosphere, but is an important greenhouse gas that contributes to the warming of the Earth, and is also essential for photosynthesis, supplying plants and animals with their ultimate source of carbon.

Greenhouse Gases

Many of the variable components of the atmosphere are particularly relevant to a discussion about global climate change because they absorb long wave infrared radiation (IR, or heat). These gases are referred to as greenhouse gases (GHGs) because they function similar to a greenhouse, and include H2O, CO2, CH4 N2O, O3, and CFCs.

Greenhouses are used for growing plants in cold seasons, and are made of glass or plastic roofs and walls, which allow in sunlight (see Figure 2). When the sunlight reaches the plants and soil, or any other surface in the greenhouse, it is absorbed and converted into IR or heat. The glass/plastic roof retains this heat so that plants can grow inside during cold winters.

Figure 3. The greenhouse effect. Solar short-wave radiation (light) entering the atmosphere is absorbed by the Earth’s surface and emitted as long-wave infrared radiation (heat) that is then absorbed by greenhouse gases which heats the atmosphere. 4

Like the glass or plastic of a greenhouse, the Earth’s atmosphere is nearly transparent to the incoming solar radiation, which is mainly composed of short wavelength radiation (light). As a result, most of the sunlight passes through the atmosphere without being absorbed. When sunlight reaches Earth, it is absorbed by liquid and solid structures such as water, soil, plants, and buildings. Once the light is absorbed, it is converted into long-wavelength infrared radiation (IR), or heat. This heat warms the surface of the planet, making it suitable for life on Earth. In this way, the Earth’s thin layer of atmosphere helps to keep the Earth warm just as greenhouse glass/plastic helps maintain heat within the greenhouse structure.

The Earth’s surface reflects some of the solar radiation that it receives back out into space. This reflectance is referred to as Earth’s albedo, and it varies from region to region. Natural concentrations of atmospheric greenhouse gases absorb this released IR, thereby slowing the loss of heat from the Earth into space (see Figure 3). This phenomenon, called the greenhouse effect, when in balance, helps maintain the range of temperature on Earth suitable for living organisms.

Without the greenhouse effect, Earth’s average surface temperature would be -18°C (0°F), too cold to support most plant and animal life. However, too much greenhouse gas in the atmosphere has caused the global climate change and warming impacts that the Earth is experiencing today.

Different greenhouse gases (GHGs) have different capacities for trapping heat. For example, among the five major greenhouse gases, water vapor is the most abundant and contributes to 90% of the greenhouse effect. Whereas methane (CH4) and nitrous oxide (N2O) are not as abundant as carbon dioxide (CO2), they are 20 and 300 times more potent than CO2 in trapping heat, respectively.

Looking Ahead

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Fossil fuels and forests have instrumental value for human life. However, when we use these resources in a way that is not sustainable for Earth’s atmosphere we morally violate the intrinsic value of nature. This issue is discussed in the upcoming Biodiversity and Ethics section.

Human activities such as burning fossil fuels (coal, oil, and natural gas), industrial agricultural practices, and deforestation have caused the concentrations of greenhouse gases in the atmosphere to increase precipitously since the beginning of the Industrial Revolution in the mid-eighteenth century (Figure 4).

Industrial agricultural practices produce more greenhouse gas emissions than any other single human activity through the manufacture of inorganic fertilizers, operation of field machinery, transportation of supplies to farms and food to market, and the energy required for pump irrigation.

Deforestation world-wide is primarily conducted to expand agriculture and development, and removes an enormously important “sink” of carbon dioxide by removing the dense forest vegetation. By removing the photosynthetic vegetation which “takes up” carbon dioxide, we effectively increase concentrations of greenhouse gases in the atmosphere.

For example, average global atmospheric carbon dioxide has increased from 280 ppm to over 400 ppm since the mid-eighteenth century. In November, 2018 greenhouse gas levels in the atmosphere broke all previously recorded high levels. Check the US National Oceanic & Atmospheric Administration – NOAA for the current concentration of CO2 in the atmosphere. Increased carbon dioxide has amplified the greenhouse effect and, as a result, has contributed to a rise in the surface temperature of the Earth. A more detailed discussion of how burning fossil fuels disrupts the natural balance of the Earth’s carbon cycle is described later in this chapter.

concentrations of greenhouse gases graph
Figure 4: Atmospheric concentrations of 3 greenhouse gases (carbon dioxide,methane, and nitrous oxide) over the last 2,000 years. Note that each of these gases has increased since 2005, and CO2 is now hovering around 400 ppm. You can see the most recent concentration values of these greenhouse gases at the Carbon Dioxide Information Analysis Center. 5

Questions to Consider

Do you have any elders in your family or among your friends and neighbors who you can talk to about climate? If so, ask them if they have personally experienced a change in weather patterns and climate in the course of their lives.

If they have experienced changes in climate in their lives, what factors do you think might go into explaining these changes?

What meaning do their experiences have for the way you think about weather patterns and climate?