I. Review of "Air"
II. Introduction to the Greenhouse Effect
III. Major Greenhouse Gases
IV. Facts Confusing & Confirming Global Warming
V. Potential Adverse Effects of Global Warming
VI. President Clinton's Climate Change Proposal
Air is characterized as an aerosol.
Gases and particles with small settling velocity that exhibit stability in a gravitational field.
Recall atmosphere layers
Troposphere 0-17 kilometers (¾ 11 miles)
Stratosphere 17-50
Mesosphere 50-90
Ionosphere 90-100
95% of the air by weight is contained in the Troposphere.
Layers of the earth's atmosphere.
The temperature of the earth's atmosphere as a function of height.
The pressure of the atmosphere as a function of altitude.
| Component | Percentage by Weight | Fraction of Total Molcules |
|---|---|---|
| N2 | 75.51 | 0.7808 |
| O2 | 23.14 | 0.2095 |
| 40Ar | 1.28 | 0.0093 |
| Water Vapor | 0.0004 |
| Component | ppm (parts per million**) |
|---|---|
| Carbon dioxide CO2 | 325.0 |
| Ne | 18.0 |
| He | 5.0 |
| CH4 | 2.0 |
| Kr | 1.0 |
| H2 | 0.5 |
| N2O | 0.5 |
| Xe | 0.1 |
Concentrations of various species in the atmosphere as a function of altitude.
Solar radiation striking the earth.
Earth maintains its temperature because of its atmosphere.
Between 0 ° C and < 100 ° C
The moon is at the same place in the solar system and it is at an average of -18 ° C (0 ° F), with extremes of -150 ° C to +100 ° C
Average temperature of Earth is 15 ° C (59 ° F)
Thermal barrier to prevent Troposphereic mixing
with Stratosphere.
Ozone layer in stratosphere also acts as a
thermocline to prevent mixing (notice chart of
atmosphereic temperature)
Light from Sun enters Earth as UV-VIS and leaves as IR Transparent to components in air on the way in and not as transparent to air components on the way out.
Earth is 10-30 ° C and radiates at 4,000 to 100,000 nm { 4 to 100 µ m } in the IR band.
H2O vapor strongly absorbs radiation 4,000 nm to 7,000 nm { 4-7 µ m }
CO2 gas strongly absorbs radiation 7,000 to 13,000 nm { 7-13 µ m }
Remember IR spectroscopy from Organic chemistry?
About 70% of the IR radiation does escape the earth, but about 30% is absorbed by CO2, H2O (and other greenhouse gases) and warms the troposphere and the earth's surface. Both radiate IR in all directions to earth & to space.
An equilibrium is established which accounts for the earth's surface temperature this is the greenhouse effect. It is an increase in the shift of this equilibrium that will increase the average temperature of the earth's surface.
Remember Le Chatelier's principle and shifting equilibrium 30/70
UV-VIS + Earth transformed to Heat (IR) + absorbed by Atm (CO2)
Methane is 1.7 ppm in atmospheric concentration and increasing by 1.2% per year.
From bacteria, termites, cows (ruminating animals) and anthropogenic sources such as the release of natural gas, we are increasing CO2 level.
Increases in atmosphereic concentration of CO2.
Increases in average concentrations of major greenhouse gases.
How do we know? Are we sure?
Earth's temperature has fluctuated over geologic time of earth
Ice ages last about 100,000 years each
Warmer periods last 10,000 to 13,000 years between (interglacial periods)
We are 10,000 years into this interglacial period
Ice age to warm period change sea level by 300 ft
With ice ages and interglacial periods CO2 levels fluctuate and dramatic changes have previously occurred.
But not at this rate of change
In the past 160,000 H2O has remained relatively constant but CO2 has fluctuated by a factor of 2
Earth surface temperature seems to follow CO2
Levels of greenhouse gasses has risen and most is anthropogenic
CO2 and CFCs accounting for 55% of increase
US emits largest quantity of greenhouse gasses (18% of global emissions) Compared to:
13.5% Soviet Union
9.1% China
5% Japan
4% India
4% Brazil
3.4% Germany
Deforestation may account for 20-33% of rise in CO2
Oceans have absorbed 30-50% of emitted CO2
Estimated rise of 0.3 to 0.6 ° C since 1860
8 out of 13 years were hotter than normal from 1980 - 92
Text
"We don't know enough about how Earth works to make accurate projections about the possible effects of our inputs of greenhouse gases on global and regional climates and on the biosphere."
Example of prediction problem -
Mount Pinatubo Philippine volcano - could cause 0.6
° C lowering by reflection of light from aerosols it
placed in upper troposphere.
Mathematical models predict a 1.5 to 5.5 ° C temperature range rise by 2050
Sun output power varies by 0.1% in 11 and 80 year cycles
Man and nature stir up dust that reflects light before it reaches the Earth and these effects cool the Earth
Water availability - droughts
Water levels of the ocean - ice caps melting
30-70% drop in food production world wide
The cloudy crystal ball as described by the text
We do not know the result
Denial and Delay
Energy conservation
Energy shifts to other forms
What should we do?
Thursday October 23, 1997
Text of President Clinton's Announcement
of the United States Policy on Climate Change
As Delivered to the National Geographic Society,
Washington, D.C., Oct. 22, 1997
Introduction to Environmental Science Home Page
