An introduction to the global energy balance global warming Notice:
We now are prepared to examine the influence of these seemingly insignificant amounts of gas on the energy balance of our planet.
First, we examine what we mean by energy balance. Energy Balance Energy Balance An initial point of clarification is necessary for those students without background in the earth or physical sciences. When we use the term "radiation" in this course we are considering components of solar emissions "sunshine" and thermal emissions from the earth.
These definitions do not include nuclear or cosmic radiation. Likewise, the term "radiatively active" refers to emission or absorption of visible light or thermal infrared energy as from a wood-burning stove.
So, except for the ultra violet component of solar radiation, the radiant energy we discuss in this course is benign to humans.
Global Heat Balance: Introduction to Heat Fluxes: The energy enters these water bodies at the surface when absorbed radiation is converted into heat energy. The warmed surface water is then transferred downward into the water column by . Introduction to hydrology and the water balance. The science of hydrology The science that describes and predicts the occurrence, circulation and distribution of the earth’s water. There are two principal foci: • The global hydrologic cycle: Transfers of water between the land, prominent role global energy flows • Density of water at. Chapter 5: The global energy balance. FLASHCARDS. LEARN. WRITE. SPELL. TEST. MATCH. GRAVITY. Upgrade to remove ads. Only $1/month. Define the global energy balance. CLICK THE CARD TO FLIP IT. TAP THE CARD TO FLIP IT. In equilibrium, the amount of energy the Earth receives from the Sun is balanced by the amount it loses back to space.
The earth receives energy from the sun, mostly in the form of visible radiation, as we showed in a previous unit. At the top of the atmosphere, a plane perpendicular to the line from the sun receives about W m The daily amounts of energy per unit area at different points on the earth are shown in Figure 1.
Note that the location receiving the maximum daily radiation is the South Pole in December! The detailed pathways for this energy transformation determine the climate conditions of our planet. The composition of the planet's atmosphere and the characteristics of the planet surface control the temperature distribution at the planet surface and hence the motions and processes of its atmosphere.
Once the visible solar energy is absorbed by the earth system - be it in clouds, the free atmosphere, or at the surface - it is transformed from electromagnetic energy to heat energy.
This absorbed energy either raises the surface temperature or evaporates surface water to create atmospheric water vapor. If an object has a temperature higher than its surroundings, then it will lose energy to its surroundings by infrared radiation.
Infrared radiation is not detectable by the human eye but can be detected by absorption by human skin. A heating element in an electric oven radiates with both infrared and visible radiation if it is glowing. If the current is turned off, it gradually loses its glow its visible radiation but continues to emit IR radiation, which can be felt by a hand close to the heating element.
The earth, compared with outer space, is very warm, and so it radiates energy away to outer space at a rate that is proportional to the fourth power of the temperature. Some of this energy radiated from the surface of the earth is directly lost to outer space, while some is absorbed by gases and clouds in the atmosphere.
This absorption of infrared radiation by a planet's atmosphere is called the "greenhouse effect".
Nitrogen, the dominant gas in the atmosphere, does not absorb infrared radiation, but oxygen, the second most abundant gas, does absorb in certain wavelength regions. Water Vapor Water Vapor Water vapor as distinct from clouds, which are treated separately is a strong absorber of infrared radiation.
If you have been in both humid and dry climates and experienced the temperature change from day to night, you will have observed that in dry climates the temperature decreases rapidly near sunset, whereas in a humid climate, the drop in temperature is much less pronounced.
The difference is due to radiation from the surface that is absorbed by water vapor in the humid atmosphere and re-radiated back to the surface. In the dry climate, this outgoing radiation penetrates the atmosphere and escapes from the earth to outer space.
So, in fact, water vapor is the largest absorber of infrared radiation from the earth and is therefore the most important greenhouse gas in the earth's atmosphere. Clouds Clouds Clouds also strongly absorb infrared radiation. In fact, a dominant factor a meteorologist must consider in forecasting nighttime temperatures for a given location is whether or not clouds will be present.
Infrared radiation emitted upward by the earth is absorbed by clouds and re-radiated back to the surface of the earth, keeping the surface temperature from decreasing very much at night. Under clear skies and low humidity very little infrared radiation returns to the earth, allowing nighttime temperatures drop more significantly.
Trace Gases Trace Gases Other trace gases in the earth's atmosphere also absorb infrared energy. Carbon dioxide, nitrous oxide, methane, ozone, and the CFCs all are greenhouse gases.
They absorb and re-radiate infrared radiation both upward and downward and contribute to maintaining a surface temperature that is higher than it would be in their absence.
We have seen in our study of atmospheric chemistry that many of these trace gases are produced by humans through the use of combustion engines and other activities. By increasing the atmospheric concentrations of these gases, we are contributing to an enhanced warming of the earth's surface by the increased greenhouse effect.
Current concentrations of greenhouse gases are posted by the Carbon Dioxide Information Analysis Center. We will come back to this topic as we seek to quantify the magnitude of this effect.
Quantifying the Global Energy Balance Quantifying the Global Energy Balance We can summarize and quantify these concepts by defining the energy balance for the earth as is shown in Figure 2.The difference between incoming shortwave and outgoing long-wave energy is not explained, which more advanced learners should understand.
Comment from expert scientist: It's a great introduction to the concept of energy balance on Earth's atmosphere.
Introduction We have devoted considerable attention to trace gases (including water vapor) in the atmosphere, their sources, sinks, lifetimes and vertical distribution.
Quantifying the Global Energy Balance For carbon dioxide, the radiative forcing (atmospheric heating rate) is proportional to the natural logarithm of the concentration. Chapter 2 The global energy balance We consider now the general problem of the radiative equilibrium tempera-ture of the Earth.
The Earth is . LECTURE THREE The Global Energy Balance CLASS LECTURE: GLOBAL ENERGY BUDGET: Review the power point lecture from class. Warning: this may not have the most up to date file. the global energy balance Table lists the various parameters for some of the planets and compares approximate measured values, T m,withT e computed from Eq.().
Global Heat Balance: Introduction to Heat Fluxes: The energy enters these water bodies at the surface when absorbed radiation is converted into heat energy. The warmed surface water is then transferred downward into the water column by .