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earth's atmosphere, past and present - Weber State University

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EARTH’S ATMOSPHERE,<br />

PAST AND PRESENT<br />

1. Introduction: the nature of matter<br />

2. Evolution of Earth’s <strong>atmosphere</strong><br />

3. Present-day composition of the <strong>atmosphere</strong><br />

4. Atmospheric density, pressure <strong>and</strong> structure<br />

5. Ozone depletion: a separate but related problem


Earth’s <strong>atmosphere</strong>: a thin envelope of gases.<br />

Source: <strong>Weber</strong> <strong>State</strong> <strong>University</strong> HARBOR balloon flight, August 2009.


THE NATURE OF MATTER:<br />

Elements <strong>and</strong> compounds, atoms <strong>and</strong> molecules.<br />

Chemical element: A pure chemical substance composed<br />

of atoms with the same number of protons in the atomic<br />

nucleus (atomic number).<br />

Source: International Union of Pure <strong>and</strong> Applied Chemistry Compendium of Chemical<br />

Terminology (Gold Book), http://goldbook.iupac.org/index.html.


Schematic showing the structure of an oxygen atom.<br />

8 electrons (-)<br />

Nucleus:<br />

8 protons (+)<br />

(= atomic number)


THE NATURE OF MATTER:<br />

Elements <strong>and</strong> compounds, atoms <strong>and</strong> molecules.<br />

Chemical element: A pure chemical substance composed<br />

of atoms with the same number of protons in the atomic<br />

nucleus.<br />

Chemical compound: A pure chemical substance<br />

consisting of two or more different chemical elements<br />

that can be separated into simpler substances by<br />

chemical reactions.<br />

Source: International Union of Pure <strong>and</strong> Applied Chemistry Compendium of Chemical<br />

Terminology (Gold Book), http://goldbook.iupac.org/index.html.


Structure of a water molecule. Source: Christopherson, 2003, p. 183.<br />

Chemical formula: H 2 O<br />

Two hydrogen atoms<br />

One oxygen atom


Chemical compounds in Earth’s <strong>atmosphere</strong>:<br />

molecules of five major greenhouse gases.<br />

Source: Mann <strong>and</strong> Kump, 2009, p. 14.


Present-day<br />

composition<br />

of Earth’s<br />

<strong>atmosphere</strong>.<br />

Source: Mann <strong>and</strong> Kump, 2009, p. 12.


Structure of a water molecule. Source: Christopherson, 2003, p. 183.<br />

POSITIVE<br />

CHARGE<br />

HYDROGEN<br />

(H + )<br />

HYDROGEN<br />

(H + )<br />

OXYGEN<br />

(O 2- )<br />

NEGATIVE CHARGE


Physical states <strong>and</strong> phase changes of water.<br />

Source: Christopherson, 2009, p. 181.


THE NATURE OF MATTER:<br />

Elements <strong>and</strong> compounds, atoms <strong>and</strong> molecules.<br />

Isotope: Atoms of the same element having the same<br />

atomic number but different mass numbers (atomic<br />

mass).<br />

Source: Mann <strong>and</strong> Kamp, 2009, p. 201; Houghton, 2009, p. 422.


Schematic showing the structure of an oxygen atom.<br />

8 electrons (-)<br />

Nucleus:<br />

8 protons (+)<br />

8, 9, or 10 neutrons<br />

Atomic number = 8<br />

Atomic mass (mass number) = 16, 17 or 18 ( 16 O, 17 O or 18 O)


EVOLUTION OF EARTH’S ATMOSPHERE<br />

(Source: After Christopherson, 1997)<br />

Age<br />

(bn. yrs BP)<br />

Composition<br />

Features<br />

4.6 to 4.0 H 2 O, HCN, NH 3 ,<br />

CH 4 , S, Cl, others<br />

4.0 to 3.3 At 4.0: H 2 O, CO 2 ,<br />

N 2 , S, hydrocarbons,<br />

little/no free O 2<br />

3.3 to 0.6 At 3.0: CO 2 , H 2 O,<br />

N 2 ,


HYDROSPHERE<br />

BIOSPHERE<br />

ATMOSPHERE<br />

LITHOSPHERE


Evolution of Earth’s <strong>atmosphere</strong> over<br />

billions of years shows that<br />

composition is DYNAMIC, not static,<br />

i.e. it can <strong>and</strong> does change over time.


Present-day<br />

composition<br />

of Earth’s<br />

<strong>atmosphere</strong>.<br />

Source: Mann <strong>and</strong> Kump, 2009, p. 12.


Changes in greenhouse gas<br />

concentrations in the <strong>atmosphere</strong>,<br />

10,000 years ago to 2005 AD.<br />

Source: Mann <strong>and</strong> Kump, 2009, p. 33.


Changes in<br />

greenhouse gas<br />

concentrations in<br />

the <strong>atmosphere</strong>,<br />

1000 to 2001 AD.<br />

Source: IPCC, 2001. See also<br />

Houghton, 2009, pp. 39 <strong>and</strong> 52.


Recent carbon<br />

dioxide<br />

increases in<br />

the context of<br />

the last 1000<br />

years.<br />

Source: Arctic Climate<br />

Impact Assessment, 2004.


Changes in carbon dioxide concentrations in the<br />

<strong>atmosphere</strong>, 10,000 years ago to 2005 AD.<br />

Source: Houghton, 2009, p. 39.


Changes in methane <strong>and</strong><br />

nitrous oxide concentrations<br />

in the <strong>atmosphere</strong>, 10,000<br />

years ago to 2005 AD.<br />

Source: Houghton, 2009, p. 52.


Atmospheric concentration of CFC-11. Source: IPCC, 1996.


Smog in the Wasatch Front/Salt Lake City area.<br />

Source: Salt Lake Tribune, 2002.


Smog in the Wasatch<br />

Front/Salt Lake City<br />

area, during <strong>and</strong> after<br />

an inversion.<br />

Source: Salt Lake Tribune, 2007.


Total atmospheric aerosols, average August-October 2001.<br />

Source: MODIS satellite observations, Houghton, 2009, p. 59.


Pollution’s effects on clouds: more reflective, less rainy.<br />

Source: Houghton, 2009, p. 61.


Computer model simulations of climate warming<br />

with <strong>and</strong> without effects of sulphate aerosols (SO 4 ).<br />

No sulphate<br />

aerosols<br />

Sulphate<br />

aerosols<br />

constant at<br />

2000 level<br />

Source: Houghton, 2009, p. 60.


Source: Christopherson,<br />

2009, p. 64.


Height in<br />

kilometres<br />

Height in<br />

miles<br />

Source: Christopherson, 2009, p.64.<br />

Atmospheric pressure in<br />

millibars


Layers in the <strong>atmosphere</strong>.<br />

Source: Mann <strong>and</strong> Kump, 2009, pp. 12 <strong>and</strong> 38.


Source: Christopherson, 2009, p63.<br />

Height in<br />

kilometres<br />

Height in<br />

miles<br />

Thermosphere<br />

Mesosphere<br />

Stratosphere<br />

Troposphere<br />

Temperature


Rising air flattens out when it hits the tropopause:<br />

an anvil cloud (cumulonimbus incus).<br />

Source: NASA Earth Science Picture of the Day, http://epod.usra.edu


Atmospheric concentration of CFC-11. Source: IPCC, 1996.


Antarctic ozone hole as measured by NASA<br />

TOMS instrument, September 11 2003.


Source:<br />

Christopherson,<br />

2009, p. 71.

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