Greenhouse Gases &
The Greenhouse Effect
Gases surrounding Earth's surface trap and absorb the Sun's radiation. Portions of that radiation escape through Earth's atmosphere, while most is re-radiated back to Earth's surface. This transfer of energy results in warming of the Earth via the "Greenhouse Effect," and drives Earth's climate. The natural Greenhouse Effect makes Earth a habitable place for human beings and other living things. The gases responsible for absorbing the Sun's radiation within our atmosphere are known as greenhouse gases. Use the image carousel to the left to view how the energy is trapped and radiated back to Earth's surface.
As the concentration of greenhouse gases in the atmosphere continues to rise, the amount of solar and infrared radiation trapped within our atmosphere increases, leading to an increase in global temperatures. While greenhouse gases are naturally occurring in the atmosphere, anthropogenic, or human-related activities, contribute to higher than normal levels of these gases.
Use the image carousel below on the left to explore the rising levels of the greenhouse gases we will be referring to throughout this curriculum: carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The image and video on the right explore the change in global temperatures over the last century.
Global Monthly Mean CH4: Major agricultural sources of methane include livestock, manure management, rice management, and biomass burning (1). Graphic Credit: Ed Dlugokencky, NOAA/GML (3)
Global Monthly Mean N2O: Major agricultural sources of Nitrous Oxide include manure management, fertilizer applications, and biomass burning (1) Graphic Credit: Ed Dlugokencky, NOAA/GML (4)
We will be using the Scripps Keeling Curve below to review historic levels of carbon dioxide. Click on the screenshot of the website below to open it in a new tab. You will only need to toggle between the time period below the latest CO2 reading. Please expand the text below and follow for instructions on navigating the graphs, though interacting with Scripps site itself will not affect your ability to proceed to the next page.
800,000 years
Select 800K Years on the far right of the Scripps graph.
Atmospheric carbon dioxide levels have cyclically fluctuated for 100,000s of thousands of years between 190 and 290 ppm indicating periods of warmer global temperatures at periods of times where CO2 levels were higher and periods of cooler global temperatures where CO2 levels were lower. After year 0, CO2 begin to consistently remain above 300ppm.
You may collapse this page, or just select the 1700-Present page.
1700-Present
Select the 1700-PRESENT from the time navigation pane on the Scripps graph.
After 1900, the global concentration of CO2 remains above 300 ppm and continues to increase to present day.
You may collapse this page, or just select the Two Years page.
Two Years
Select TWO YEARS from the time navigation pane on the Scripps.
This graph is a zoomed in version of the last two years of the previous graph. Levels of CO2 naturally oscillate throughout the year. Periods of higher atmospheric levels of CO2 correspond to times of the year of peak plant productivity where CO2 is removed from the atmosphere through photosynthesis (we will refer back to this later). Periods of higher CO2 concentrations reflect times of lower photosynthetic activity.
You may collapse this page, or just proceed past the Scripps graph below.
Different land uses contribute different amounts of emissions. By order of land use contribution to emissions in the United States, these land uses include transportation, electricity, industry, commercial/residential, and agriculture (EPA). If you would like to investigate emissions by sector outside of this curriculum, check out EPA's Greenhouse Gas Inventory Data Explorer.
This curriculum is focused on the agricultural sector and will be investigating how implementing conservation and carbon farming practices can mitigate the impacts of climate change, thus reducing the agricultural contributions to climate change.
Greenhouse Gas Emissions on Working Lands
Carbon dioxide (CO2) is emitted from respiration of soil microbes, burning of biomass, liming and urea applications, clear-cutting events, fuel emissions from machinery
Methane (CH4) is released from livestock (ruminant) digestive processes, manure management, rice management, and biomass burning.
Nitrous oxide (N2O) is released to the atmosphere through the application of synthetic and organic fertilizers, nitrogen fixing crops, manure management, and biomass burning (7).
While some greenhouse gas emissions on working lands result from natural processes, conventional practices have exacerbated the rate at which these are emitted from the working lands. We will explore these and conservation and carbon farming practices that can reduce those emissions.
The enhanced Greenhouse Effect is rapidly making Earth unsuitable for human beings and other living things through rising temperatures, increased intensities of storms and droughts, and changing pest and disease pressures, among other impacts. With the ability to naturally sequester carbon, agriculture has the potential to mitigate impacts of climate change by reducing greenhouse gases in the atmosphere, thus reducing global temperatures. We will also explore how carbon farming can improve the resilience of working lands in the face of climate change.
New York Times "Every Country Has Its Own Climate Risks. What's Yours? By Yaryna Serkez. Major agricultural lands are threatened by droughts, flooding, wildfires, and extreme heat.
❓Check your knowledge!
In what ways does agriculture contribute to climate change and GHG emissions? (select all that apply)
a. Excessive inorganic nitrogen in the soil
b. Excessive inorganic phosphorus in the soil
c. The loss of soil organic carbon via microbial respiration
d. Methane emissions from ruminants and manure management practices
e. Implementing practices that contribute to greater carbon losses than carbon gains