geography worksheet 2

Account for the Greenhouse Effect (one layer atmosphere model)

σTs 4 =

S 4 1− Albedo( )+σTe

4

σTs 4 = 2σTe

4

σTe 4 =

S 4 1− Albedo( )

Ts = 2 1 4Te240 Wm-2 coming into surface

240 Wm-2 leaving into space

340 Wm-2 available before accounting for albedo

*Remember S is the solar constant 1365Wm2

Ts is earth surface temp. Te is temp at the top of the atmosphere where energy is radiated back to space

1)

2)

3)

4)

Here is our one layer atmosphere model that we reviewed previous week. Although this is a great model to help us learn how a climate model works, it is a little too simple to represent our true atmosphere.

Can you think about what is unrealistic about this layer model? Although there are a number of answers, what stands out most in terms of the greenhouse effect is that 1) not all atmospheric gases are greenhouse gases; and 2) the temperature of the atmosphere is not vertically homogenous.

1) Not all atmospheric gases are greenhouse gases. This layer model is based upon a simple concept of “what goes in, must come out”. With this, in the second equation, the Earth’s back radiation is completely absorbed by the atmosphere (greenhouse gases) and radiated equally back to the surface of Earth and to space (equation 2, in slide). However, in reality, we all know that greenhouse gases are definitely not a major component of the atmosphere! This week, let’s talk about what make greenhouse gases – greenhouse gases! After this week, you should be able to explain “what are greenhouse gases” from a slightly different perspective – in a quantum mechanical way.

2) temperature of the atmosphere is not vertically homogenous. Of course, when you are away from a heat source (in this case, the surface of the Earth), temperature decreases. However, such diffusion cannot be expressed by a simple layer model. Therefore, climate scientists combine multiple layer models vertically and horizontally to make a climate model close to reality.

Composition of the Atmosphere including variable components (by volume)

As we learned in previous lectures, major composition of the atmosphere is nitrogen, oxygen, and argon. Very interestingly, greenhouse gases consist of only a fraction of the atmosphere, and are called trace gases.

Radiative forcings, IPCC 2013

That said, although small, these gases are important in altering the Earth’s energy budget. Based on the IPCC’s (Intergovernmental Panel on Climate Change) assessment report (IPCC 2007), greenhouse gases, such as CO2, CH4, N2O, and Halocarbons, show positive radiative forcing. This means that these gases contribute to warming of the atmosphere.

CO2 carbon dioxide CH4 methane

N2O nitrous oxide

Important to note that, although we are focusing on CO2 to examine climate sensitivity here, we all know that there are other molecules that can absorb long wave back radiation: water molecules (H2O), methane (CH4), nitrous oxide (N2O), etc.

Elements Atoms

Nucleus Protons (+) Neutrons (o)

Electrons (-)

• All matter, including minerals, rocks, and gas molecules, are made of atoms

The chemical composition First, let’s review basic chemistry.

Atoms

• Smallest particle into which an element can be divided while still retaining the chemical characteristics of that element

Here is an example of an oxygen atom. This conceptualized view is only an approximation or model showing the nucleus of the atom surrounded by orbiting electrons (middle figure). A more realistic view consists of electron shells surrounding the nucleus. Electrons are in the probability clouds (far right figure). This expression is based on quantum mechanics.

Carbon atom

Electron cloud

Nucleus

Composed of a nucleus surrounded by electrons Nucleus is composed of protons (+) and neutrons (0)

Carbon atom

Electron cloud

Nucleus

Carbon has 6 electrons…

Electron (–)

Proton (+) Neutron

Number of neutron adds mass to the atom.

Number of electrons (-) orbiting nucleus determined by the number of positively charged protons.

Negatively charged electrons balance the positive charges of the protons.

Carbon atom

Electron cloud

Nucleus

Carbon has 6 electrons…

…and a nucleus of 6 protons …

…and 6 neutrons.

Electron (–)

Proton (+) Neutron

Number of protons defines the chemical element and atomic number (e.g. atomic number of hydrogen (H) is 1, He is 2, Li is 3, …)

ION = Charged Particle

CATION = Positive Charge (lose electrons, i.e., Fe+2)

ANION = Negative Charge (gain electrons, i.e., O-2)

BONDING Each atom may or may not be connected to other atoms

with different types of bonding. Here, we learn three major bondings: ionic bond, covalent bond, and

hydrogen bond.

Sodium atom Chlorine atom

Ionic Bond Here is an example of NaCl, also know as salt.

Sodium loses one electron… …and chlorine acquires it.

Electrical attraction

Sodium atom Chlorine atom Cation (+) Anion (–)

Ionic Bond Sodium and chlorine are attracted to each other and create ionic bonding.

Carbon atoms are arranged in regular tetrahedra…

…that share electrons with neighboring atoms.

Carbon atoms Electrons

Nucleus

Covalent Bond

Covalent bond is one of the strongest bonds. In this type of bonding, the atoms share an electron with adjacent atoms, so they are not easily separable. Examples of covalent bonds are ozone (O3), hydrogen (H2), water (H2O), methane (CH4), ammonia (NH3), and CO2 (carbon dioxide).

The Hydrogen Bond • Chemistry of water

– Atoms and molecules – Two hydrogen and one oxygen molecule (H2O) – Covalent bonds – Electrical polarity

of water molecule – Hydrogen bonds

The hydrogen bond is a unique and weak bond. It is the electrostatic attraction

between two polarized groups of atoms/molecules. One most famous example is a water molecule. Although, as we saw in the previous slide that a water

molecule is a covalent bond, the bonds connecting water molecules are

hydrogen bonds. This occurs because the molecular structure of water is

unique and naturally polarized (electronically imbalanced) – I call this

molecular structure a Mickey Mouse structure! Because water molecules are polarized, each molecule is attracted electrostatically. Therefore, water has a

wonderful surface tension. In our childhood, we all tried to put as many water

drops as possible on a surface of the coin… We are able to do this because of

the hydrogen bond.

Okay – let’s continue to learn about greenhouse gases in the following lecture

slides.