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

EARTH’S ATMOSPHERE,
PAST AND PRESENT
1. Introduction: the nature of matter
2. Evolution of Earth’s atmosphere
3. Present-day composition of the atmosphere
4. Atmospheric density, pressure and structure
5. Ozone depletion: a separate but related problem

Earth’s atmosphere: a thin envelope of gases.
Source: Weber State University HARBOR balloon flight, August 2009.

THE NATURE OF MATTER:
Elements and compounds, atoms and molecules.
Chemical element: A pure chemical substance composed
of atoms with the same number of protons in the atomic
nucleus (atomic number).
Source: International Union of Pure and Applied Chemistry Compendium of Chemical
Terminology (Gold Book), http://goldbook.iupac.org/index.html.

Schematic showing the structure of an oxygen atom.
8 electrons (-)
Nucleus:
8 protons (+)
(= atomic number)

THE NATURE OF MATTER:
Elements and compounds, atoms and molecules.
Chemical element: A pure chemical substance composed
of atoms with the same number of protons in the atomic
nucleus.
Chemical compound: A pure chemical substance
consisting of two or more different chemical elements
that can be separated into simpler substances by
chemical reactions.
Source: International Union of Pure and Applied Chemistry Compendium of Chemical
Terminology (Gold Book), http://goldbook.iupac.org/index.html.

Structure of a water molecule. Source: Christopherson, 2003, p. 183.
Chemical formula: H 2 O
Two hydrogen atoms
One oxygen atom

Chemical compounds in Earth’s atmosphere:
molecules of five major greenhouse gases.
Source: Mann and Kump, 2009, p. 14.

Present-day
composition
of Earth’s
atmosphere.
Source: Mann and Kump, 2009, p. 12.

Structure of a water molecule. Source: Christopherson, 2003, p. 183.
POSITIVE
CHARGE
HYDROGEN
(H + )
HYDROGEN
(H + )
OXYGEN
(O 2- )
NEGATIVE CHARGE

Physical states and phase changes of water.
Source: Christopherson, 2009, p. 181.

THE NATURE OF MATTER:
Elements and compounds, atoms and molecules.
Isotope: Atoms of the same element having the same
atomic number but different mass numbers (atomic
mass).
Source: Mann and Kamp, 2009, p. 201; Houghton, 2009, p. 422.

Schematic showing the structure of an oxygen atom.
8 electrons (-)
Nucleus:
8 protons (+)
8, 9, or 10 neutrons
Atomic number = 8
Atomic mass (mass number) = 16, 17 or 18 ( 16 O, 17 O or 18 O)

EVOLUTION OF EARTH’S ATMOSPHERE
(Source: After Christopherson, 1997)
Age
(bn. yrs BP)
Composition
Features
4.6 to 4.0 H 2 O, HCN, NH 3 ,
CH 4 , S, Cl, others
4.0 to 3.3 At 4.0: H 2 O, CO 2 ,
N 2 , S, hydrocarbons,
little/no free O 2
3.3 to 0.6 At 3.0: CO 2 , H 2 O,
N 2 ,

HYDROSPHERE
BIOSPHERE
ATMOSPHERE
LITHOSPHERE

Evolution of Earth’s atmosphere over
billions of years shows that
composition is DYNAMIC, not static,
i.e. it can and does change over time.

Present-day
composition
of Earth’s
atmosphere.
Source: Mann and Kump, 2009, p. 12.

Changes in greenhouse gas
concentrations in the atmosphere,
10,000 years ago to 2005 AD.
Source: Mann and Kump, 2009, p. 33.

Changes in
greenhouse gas
concentrations in
the atmosphere,
1000 to 2001 AD.
Source: IPCC, 2001. See also
Houghton, 2009, pp. 39 and 52.

Recent carbon
dioxide
increases in
the context of
the last 1000
years.
Source: Arctic Climate
Impact Assessment, 2004.

Changes in carbon dioxide concentrations in the
atmosphere, 10,000 years ago to 2005 AD.
Source: Houghton, 2009, p. 39.

Changes in methane and
nitrous oxide concentrations
in the atmosphere, 10,000
years ago to 2005 AD.
Source: Houghton, 2009, p. 52.

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

Smog in the Wasatch Front/Salt Lake City area.
Source: Salt Lake Tribune, 2002.

Smog in the Wasatch
Front/Salt Lake City
area, during and after
an inversion.
Source: Salt Lake Tribune, 2007.

Total atmospheric aerosols, average August-October 2001.
Source: MODIS satellite observations, Houghton, 2009, p. 59.

Pollution’s effects on clouds: more reflective, less rainy.
Source: Houghton, 2009, p. 61.

Computer model simulations of climate warming
with and without effects of sulphate aerosols (SO 4 ).
No sulphate
aerosols
Sulphate
aerosols
constant at
2000 level
Source: Houghton, 2009, p. 60.

Source: Christopherson,
2009, p. 64.

Height in
kilometres
Height in
miles
Source: Christopherson, 2009, p.64.
Atmospheric pressure in
millibars

Layers in the atmosphere.
Source: Mann and Kump, 2009, pp. 12 and 38.

Source: Christopherson, 2009, p63.
Height in
kilometres
Height in
miles
Thermosphere
Mesosphere
Stratosphere
Troposphere
Temperature

Rising air flattens out when it hits the tropopause:
an anvil cloud (cumulonimbus incus).
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
TOMS instrument, September 11 2003.

Source:
Christopherson,
2009, p. 71.