greenhouse effect, greenhouse gases, radiative forcing

1. The CHEMISTRY of
Republic of the Philippines
BULACAN AGRICULTURAL STATE COLLEGE
INSTITUTE OF GRADUATE STUDIES
Pinaod, San Ildefonso, Bulacan

2. The CHEMISTRY of
Greenhouse Effect

3. The CHEMISTRY of
Greenhouse Effect

4. "Venus is too hot, Mars is too
cold, and Earth is just right."
-Goldilocks Principle
TheCHEMISTRYof
GreenhouseEffect

5. The CHEMISTRY of
Greenhouse Effect

6. The CHEMISTRY of
Greenhouse Effect

7. The CHEMISTRY of
Greenhouse Effect
When certain gases in the atmosphere absorb IR Radiation their
vibrational modes are excited and vibrate, causing them to collide with
other molecules and transfer energy
On a molecular level…

8. The CHEMISTRY of
Greenhouse Effect
When the electrons return to their ground state,
they re-emit the energy with a frequency equal to
the frequency of energy gap between the two
levels

9. The CHEMISTRY of
Greenhouse Effect
If this didn’t happen…
The climate would be an average of 60°F colder and the
earth could not sustain life as we know it.
Photo: CarlaB, Flickr Creative Commons

10. The CHEMISTRY of
Greenhouse Effect
So greenhouse gases are
called greenhouse gases
because they keep some heat
in the atmosphere to sustain
life on earth as a greenhouse
does to sustain life in the
greenhouse when it is cold
outside

11. The CHEMISTRY of
Greenhouse Effect
So a round of applause for
greenhouse gases !
Source: PEREZHILTON.COM

12. TheCHEMISTRYof
GreenhouseEffect Let’s find out which atmospheric
gases are green house gases
By Selena Wilke (Own work) [Public domain], via Wikimedia Commons

13. TheCHEMISTRYof
GreenhouseEffect The most abundant atmospheric gas,
Nitrogen molecules have a strong bond
which makes it chemically stable and non-
reactive in most circumstances. Nitrogen's
simple structure is unable to absorb either
visible or infrared light. As a result, nitrogen
is not a greenhouse gas.

14. TheCHEMISTRYof
GreenhouseEffect Oxygen is the second most
abundant atmospheric gas.
Why do you think that Oxygen
is also not a greenhouse
gas?

15. The CHEMISTRY of
Greenhouse Effect
Vibrations that do not
change the overall
dipole of the
molecule do not lead
to IR absorption

16. TheCHEMISTRYof
GreenhouseEffect

17. TheCHEMISTRYof
GreenhouseEffect Water vapor is the most important GHG. Along with small
water droplets in clouds, it produces somewhere between
66% and 85% of the greenhouse effect.
Water Vapor

18. TheCHEMISTRYof
GreenhouseEffect Carbon dioxide is the second most important GHG, producing some 9%
to 26% of the greenhouse effect. Carbon dioxide concentration in the
atmosphere is quite low; slightly less than 0.04%
Carbon Dioxide

19. TheCHEMISTRYof
GreenhouseEffect

20. TheCHEMISTRYof
GreenhouseEffect Methane
Methane (CH4) is 30 times stronger than carbon dioxide as an
absorber of infrared radiation. Methane however, exists in even
smaller quantities in our atmosphere than does carbon dioxide;
its abundance is usually expressed in terms of parts
per billion by volume (ppbv).

21. TheCHEMISTRYof
GreenhouseEffect

22. TheCHEMISTRYof
GreenhouseEffect Other GHGs
Halocarbons are composed of carbon, chlorine, fluorine,
and hydrogen. They include chlorofluorocarbons (CFCs),
which are man-made gases commonly used in refrigerators
and air conditioners.
Nitrous oxide (N2O), a relatively long-lived gas, has
increased in atmospheric concentration due mainly to
agriculture. Nitrate (NO3-
) and ammonia (NH4+
) are used as
fertilizers. Bacteria convert a small amount of this nitrate
and ammonia into the form of nitrous oxide. Internal
combustion engines also produce nitrous oxide.
Ozone (O3) is also a relatively minor greenhouse gas
because it is found in relatively low concentrations in the
troposphere (the lowest layer of the atmosphere). In the
troposphere, it is produced by a combination of pollutants —
mostly hydrocarbons and nitrogen oxide compounds.

23. TheCHEMISTRYof
GreenhouseEffect Two Concepts that will Help Explain
the Overall Impacts of Increases in
GHGs.
1. Radiative Forcing
2. Global Warming
Potential

24. TheCHEMISTRYof
GreenhouseEffect - measurement of the capacity of a
gas or other forcing agents to affect
the energy balance, thereby
contributing to climate change
- heating effect caused by greenhouse
gases in the atmosphere.
- change in energy in the atmosphere
due to GHG emissions.
- the difference between incoming
solar radiation and outgoing infrared
radiation caused by the increased
concentration of that gas
- expressed in Watts per square meter
(W/m2)

25. TheCHEMISTRYof
GreenhouseEffect •Positive radiative forcing results in
an increase in Earth’s energy budget
and ultimately leads to warming.
Because GHGs absorb infrared
radiation and re-emit it back to the
Earth’s surface, thus increasing the
Earth’s energy balance, they have
positive RF values.
•Negative radiative forcing results in
a decrease in the energy budget and
ultimately leads to cooling. Aerosol
particles reflect solar radiation, leading
to a net cooling, and therefore have
negative RF values.

26. TheCHEMISTRYof
GreenhouseEffect The radiative forcing of a GHG is determined by its
atmospheric concentration, warming capacity, residence
time, and spatial distribution:
1.Amount/Atmospheric Concentration
2. Warming or Cooling Capacity refers to the “strength”
or potency of an emitted gas to act as a GHG.
3. Duration/Residence Time in the Atmosphere refers to
the time a GHG stays in the atmosphere.
4. Distribution refers to how far GHGs spread
geographically.

27. TheCHEMISTRYof
GreenhouseEffect
In 2015, the Annual Greenhouse Gas Index was 1.37, which
represents a 37 percent increase in radiative forcing (a net
warming influence) since 1990 .
Of the greenhouse gases, carbon dioxide accounts for by far the
largest share of radiative forcing since 1990, and its contribution
continues to grow at a steady rate. Carbon dioxide alone would
account for a 30 percent increase in radiative forcing since 1990..
Although the overall Annual Greenhouse Gas Index continues to rise, the
rate of increase has slowed somewhat since the baseline year 1990. This
change has occurred in large part because methane concentrations have
increased at a slower rate in recent years and because chlorofluorocarbon
(CFC) concentrations have been declining, as production of CFCs has
been phased out globally due to the harm they cause to the ozone layer.

28. TheCHEMISTRYof
GreenhouseEffect
- relative measure of how much heat
a greenhouse gas traps in the
atmosphere
- developed to allow comparisons of the
global warming impacts of different
gases.
- a measure of how much energy the
emissions of 1 ton of a gas will absorb
over a given period of time, relative to
the emissions of 1 ton of carbon
dioxide (CO2).

29. TheCHEMISTRYof
GreenhouseEffect
GWP time horizon
Gas Lifetime, yr 20 yr 100 yr 500 yr
Carbon
Dioxide, CO2
see text 1 1 1
Methane, CH4 12 72 25 7.6
Nitrous
Oxide, N2O
114 289 298 153
CFC-12,
CCl2F2
100 11,000 10,900 5,200
HFC-23, CHF3 270 12,000 14,800 12,200
HFC-134a,
CH2FCF3
14 3,830 1,430 435
Sulfur
Hexafluoride,
SF6
3,200 16,300 22,800 32,600

30. TheCHEMISTRYof
GreenhouseEffect
Thank you
for
listening.