BIOL 100 Chapter Notes - Chapter 47: Atmospheric Methane, Carbon Cycle, Cyanobacteria
Textbook Notes
Chapter 47
Global Warming
Concept 1: Greenhouse Effect
Non Greenhouse Effect - The Role of the Sun
As the planet has increased in temperature, the causes could be external with the principle source being the sun
Since 1750, the average recorded energy coming from the sun remained constant or increased slightly
If the present global warming were caused by a more active sun, there would be warmer temperatures in all
layers of the atmosphere
However, data shows a cooling in the upper atmosphere, and a warming at the surface and in the lower
parts of the atmosphere
The most likely explanation is that greenhouse gases are trapping heat in the lower atmosphere
Climate models that include changes in the amount of solar heating can’t reproduce the recorded temperature
trend over the past century without including a rise in greenhouse gases
Greenhouse Effect
Heat absorption by certain gases in the atmosphere, which effectively 'traps' heat in the lower atmosphere and re-
radiates some of that heat downward
As the sun's shortwave energy heats the surface, longer-wave energy from the earth is re-radiated to the
atmosphere
Greenhouse gases absorb this energy, thereby allowing less heat to escape back to space, and 'trapping' it in the
lower atmosphere
Water vapor - most abundant greenhouse gas, followed by carbon dioxide, methane, nitrous oxide and synthetic
gases
A by-product of respiration by plants and animals
Gaseous water represents a small but environmentally significant constituent of the atmosphere
Approximately 99.13% of it is contained in the troposphere which is the lowest layer of the atmosphere
The most potent greenhouse gas owing to the presence of the hydroxyl bond which strongly absorbs in
the infra-red region of the light spectrum
The concern is not with the fact that we have a greenhouse effect, but whether the temperature increase is
injurious to the population as a whole and what factors that influence global warming we want to control
Concept 2: Carbon Dioxide
Carbon Dioxide
Natural production and absorption of this is achieve through terrestrial bops here and the ocean
Humankind has altered the natural carbon cycle by burning coal, oil, natural gas, and wood
First greenhouse gas demonstrated to be increasing in atmospheric concentration with the first conclusive
measurements being made in the last half of the 20th century
Major contributes to atmospheric carbon dioxide:
The carbon cycle as photosynthesis; plants, algae, and cyanobacteria absorb carbon dioxide, light, and
water to produce carbohydrates and chemical energy
Oxygen is produced and released as a waste product
Carbon dioxide is also produced by combustion of coal or hydrocarbons
Fermentation of liquids
Respiration of humans and animals
Emitted from volcanoes, hot springs, geysers and other places where the earth's crust is thin
CO2 is also associated with oil and gas deposits
CO2 will also dissolve in water, forming a weak acid called carbonic acid, therefore atmospheric CO2 is a major
source of ocean acidification
One of the most abundant gasses in the atmosphere
Photosynthesis - plants convert carbon dioxide and water into food compounds, such as glucose, proteins, lipids,
and oxygen
6 CO2 + 6 H2O —> C6H12O6 + 6 O2
Plants and animals, in turn, convert food compounds by combining it with oxygen to release energy for
development of ATP which is used to power anabolism and catabolism
Respiration:
C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O
Carbohydrates are oxidized in the cells and the resulting chemical is carbon dioxide
Rapid combustion - form of oxidation that is otherwise known as a fire, in which large amounts of heat and light
energy are released, which often results in a flame
Sometimes, a large volume of gas is liberated in combustion besides the production of heat and light
Complete combustion - reactant burns in oxygen, producing a limited number of products
When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water
When elements are burned, the products are primarily the most common oxides
Complete combustion is impossible to achieve
A compound reacts with an oxidizing element, such as oxygen, and the products are compounds of each
element in the fuel with the oxidizing element
Incomplete combustion - will only occur when there isn't enough oxygen to allow the fuel to react completely to
produce carbon dioxide and water
Products of pyrolysis remain un-burnt and contaminate the smoke with noxious particulate matter and
gases
Smoldering - slow, low-termpature, flameless form of combustion, sustained by the heat evolved when oxygen
directly attacks the surface of a condensed-phase fuel
Turbulent - most used for industrial application because the turbulence helps the mixing process between the fuel
and oxidizer
Modern Living and Carbon Dioxide Production
Automobiles
Burning one gallon of gas creates approximately 20 pounds of carbon dioxide, and the average car emits
about six tons of carbon dioxide every year
Heating a house
Produces about four tons of carbon dioxide per year on a national average, in addition to eight tons for
electricity use
Travel
Since the plane is already at high altitudes, the carbon dioxide that it emits is directly injected into the
Document Summary
Non greenhouse effect - the role of the sun. As the planet has increased in temperature, the causes could be external with the principle source being the sun. Since 1750, the average recorded energy coming from the sun remained constant or increased slightly. If the present global warming were caused by a more active sun, there would be warmer temperatures in all layers of the atmosphere. However, data shows a cooling in the upper atmosphere, and a warming at the surface and in the lower parts of the atmosphere. The most likely explanation is that greenhouse gases are trapping heat in the lower atmosphere. Climate models that include changes in the amount of solar heating can"t reproduce the recorded temperature trend over the past century without including a rise in greenhouse gases. Heat absorption by certain gases in the atmosphere, which effectively "traps" heat in the lower atmosphere and re- radiates some of that heat downward.
