Geography Assignment 2

Greenhouse Effect continued…

We are still here.

Climate change

The knobs that control earth’s climate: • Atmospheric composition (greenhouse effect) • Amount of solar radiation (luminosity) • What parts of Earth get radiation (orbit) • Atmospheric and ocean circulation • Earth’s albedo (fraction of solar energy reflected off earth’s

surface) • Volcanoes • Plate tectonics

We talked about climate knobs that effectively control our climate system. Rather than to understand the chaotic and complicated systems that interact with the climate system as a whole, a better way to understand climate is to focus on components (climate knobs) that strongly affect the climate system. Here, let’s learn about the first climate knobs.

Air Pollution

Smog trapped below clouds by a thermal inversion across upstate New York

Image from NASA Johnson Space Center

Although the atmosphere is a renewable resource, the atmosphere is very fluid and definitely not stable. It is the most dynamic of all of Earth’s systems. We, as human beings, both use and abuse the atmosphere. It is treated as a gigantic waste disposal system for emissions from our vehicles and industries. How people affect the atmosphere and influence global climate has become a major environmental concern for many around the world.

EOS, December 2014

The Atmosphere Gas Name Chemical Formula Percent Volume Nitrogen N2 78.08%

Oxygen O2 20.95%

*Water H2O 0 to 4%

Argon Ar 0.93%

*Carbon Dioxide CO2 0.0390%

Neon Ne 0.0018%

Helium He 0.0005%

*Methane CH4 0.00017%

Hydrogen H2 0.00005%

*Nitrous Oxide N2O 0.00003%

*Ozone O3 0.000004%

*affected by people

The most important greenhouse gases are water vapor (H2O), carbon dioxide (CO2), and methane (CH4), and they consist of only a fraction of the entire atmosphere’s composition. While water vapor can range to above 3% in the moist tropics, it is less than 1% of the atmosphere in a dry/cold environment. All of these greenhouse gases make up, on average, less than 1% of the atmosphere, and are referred to as trace gases. Although small, these gases are important in how they can impact and alter the Earth’s energy budget. Here, green-colored gases are human influenced greenhouse gases. While we are primarily talking about trace gases, it is important to note that not all trace gases are greenhouse gases.

Climate change

The knobs that control earth’s climate: • Atmospheric composition (greenhouse effect) • Amount of solar radiation (luminosity) • What parts of Earth get radiation (orbit) • Atmospheric and ocean circulation • Earth’s albedo (fraction of solar energy reflected off earth’s

surface) • Volcanoes • Plate tectonics

The Sun as a source of Energy The sun is the ultimate source of energy in our solar system. Almost all energy originates from the Sun.

• Nuclear Fusion – Hydrogen is converted

to Helium releasing tremendous energy

– 3.9 X 1026 W (watt)!

– Average distance to the Earth is ~150 X 106 km

– Surface temp. is 5800 K (kelvin)

Nuclear Fusion: At the core of the Sun, tremendous amounts of nuclear power are generated by a reaction known as nuclear fusion. Nuclear fusion is the process by which two or more smaller atomic nuclei combine to form a larger one, with an accompanying release of energy. Fusion is a process where a simple hydrogen nuclei containing one proton fuses to produce helium. Fusion is a clean energy producing process and can be used as an alternative energy source in the future. However, the process is currently too expensive to be widely commercialized.

The Sun is a natural fusion reactor, which produces magnificent amounts of energy and it’s clean energy!

For more information about nuclear fusion, pleas visit: https://energyeducation.ca/encyclopedia/Nuclear_fusion_in_the_Sun

Diagram showing the different parts of the Sun. The three parts of the atmosphere, from the surface of the Sun outward are the photosphere, chromosphere, and corona. (Credit: NASA)

Further reading about the Sun: https://imagine.gsfc.nasa.gov/science/objects/sun1.html

Video link: NASA -Introduction to the Electromagnetic Spectrum https://youtu.be/lwfJPc-rSXw

Energy travels by means of light through space in the form of waves called electromagnetic radiation. These waves span many orders of magnitude in size, or wavelength, and this range of wave sizes is known as the electromagnetic spectrum.

Energy travels by means of light through space in the form of waves. Photon – an elementary particle - carries this energy in the form of a wave. This is called electromagnetic radiation.

These waves span many orders of magnitude in size, or wavelength, and this range of wave sizes is known as the electromagnetic spectrum.

Absorption Spectra of Greenhouse Gases

Energy from the Sun moves through space in a wide range of wave forms that vary by wavelength (electromagnetic spectrum). However, the energy that drives Earth’s climate system occupies only a narrow range of this spectrum. Much of the incoming radiation energy from the Sun is scattered, reflected, or absorbed by the atmosphere. By the time it reaches the surface of the Earth, it mostly consists of visible radiation at wavelengths between 0.4 and 0.7 micrometers. Also, some ultraviolet radiation enters Earth’s atmosphere. Both are sometimes referred to as shortwave radiation (blue band in figure). Infrared radiation is a longer wavelength than visible and ultraviolet radiation and referred to as longwave radiation (red band in figure).

The shapes of the blackbody

spectra of Earth and the sun

Percentage of radiation

absorbed through the atmosphere

Absorption Spectra of Greenhouse Gases

If a chunk of matter oscillates and can interact with light at all possible frequencies, it is called a blackbody. The light (energy) that is emitted by a blackbody is called blackbody radiation. Most solids and liquids at the surface of the Earth are blackbodies. Blackbody radiation is made up of a characteristic distribution of frequencies of infrared light (red band in figures).

Thus, Earth not only absorbs energy, it emits the energy back to the space.

In the middle figure, “the shapes of the blackbody spectra of Earth and the Sun” show the band of wavelength the Sun shines with surface temperature 5800 kelvin (K) (blue band) and Earth shines in infrared light (red band) with mean surface temperature 255 K (= -18 C°, -0.4 F).

The lowest figure, “percentage of radiation absorbed through the atmosphere” explains the basics of greenhouse effect. We will come back to this later!

Blackbody (Planck) Curve

Sun’s planetary temperature 5800 K or 5526 C Incoming solar radiation = shortwave radiation

Earth’s planetary temperature 255 K or -18 C Earth’s outgoing radiation = longwave radiation

The wavelength distribution of blackbody radiation can be described mathematically by a relation called the Planck function, thus called blackbody curve or Planck curve. The important message from this figure is the spectrum of blackbody radiation is dependent on the temperature of the object. A higher temperature blackbody radiates higher energy in a shorter wavelength than a lower temperature object.

Example Test 1 question: An idealized object that absorbs all incident electromagnetic radiation and emits the maximum amount of radiation possible at every wavelength for its temperature is a(n):

A. blackbody B. isotherm C. celsius D. albedo E. kelvin

The answer is A!