C.5 Environmental Impact - Global Warming Flashcards
What are the stages of the greenhouse effect?
1 - Short wavelength radiation from the sun passes through the atmosphere without being absorbed
2 - the planets surface is warmed and its longer wavelength infrared (IR) radiation
3 - Some of this IR radiation is absorbed by greenhouse gases such as CO2
4 - Some absorbed radiation is re emitted into the atmosphere
5 - Atmospheric temperature is warmer than without the effect
How do the molecules absorb IR radiation?
All molecules vibrate but different molecules vibrate in different ways. Molecules with more than the atoms have different binational mode. A molecules will absorbs IR radiation if it possesses a VIBRATIONAL MODE (bend or stretch) which leads to a change in the DIPOLE MOMENT (polarity) of the molecule. Absorption of IR radiation promotes the molecule from a lower to a higher vibrational energy level.
Why can greenhouse gases absorb IR radiation?
Greenhouse gases such as water vapour, carbon dioxide and methane absorb IR ration because they possess bending and/or stretching vibrations that lead to a change in dipole moment.
Why do molecules such as O2 and N2 not absorb IR radiation?
They are non polar and as they vibrate they reman non polar, there is no change in dipole moment so they do not absorb IR radiation.
What is evidence for the effect of the greenhouse gases on global warming?
Atmospheric CO2 levels were fairly constant between the end of the last ice ae and the start od the industrial revolution
In the last 250 years CO2 levels have risen 200 times faster
Average global temperatures rose by 0.7 degrees Celsius in the last 100 years
Computer model tested against past data provide compelling evidence for a causal relationship
Solar and volcanic activity have been proposed as alternatives.
What is the effect of the greenhouse gas water vapour on global warming?
Water vapour comes from the evaporation from oceans and lakes and has the largest natural effect, it is a poor absorber of IR radiation but present in huge quantities compared to other greenhouse gases. Levels not influenced by humans to any real extent.
What is the effect of the greenhouse gas carbon dioxide on global warming?
It comes from the burning of fossil fuels and biomass it has the largest anthropogenic effect, it is a weak absorber of IR radiation, large quantities present.
What is the effect of the greenhouse gas methane on global warming?
It comes from the anaerobic decomposition of vegetation and animals in agriculture, it has a smaller effect than CO2, it is a good absorber of IR radiation but has a lower abundance that CO2.
How can carbon dioxide emissions be controlled?
Reduce burning of fossil fuels and move to cleaner or renewable energy source
Reduce deforestation - more trees to absorb excess CO2
Carbon capture and storage - CO2 is piped underground for storage, CO2 can also be reacted with minerals to make insoluble carbonates (soared underground).
What is global dimming?
Global dimming occurs when solar radiation is reflected back into space by particulates such as soot, ash or dust in the atmosphere as well as by clouds. Global dimming is responsible for a decrease in global temperatures.
How is the equilibrium of the atmosphere and the oceans displaced?
The following heterogeneous (different physical states) equilibrium exists between the atmosphere and the oceans:
CO2(g) CO2(aq)
Rising atmospheric levels of CO2 shifts this equilibrium to the right.
How does dissolved carbon dioxide react in the ocean?
Dissolved carbon dioxide in the oceans heat with water to form carbonic acid which then dissociates:
1 - CO2(aq) + H20(l) H2CO3(aq)
2 - H2CO3(aq) HCO3-(aq) + H+(aq)
3 - HCO3-(aq) CO32-(aq) + H+ (aq)
An increase in CO2(aq) causes equilibrium 1 to shift to the right this leads to an increase in the concentration of H2CO3 this causes equilibrium 2 to shift to the right to use up the H2CO3 which increases the concentration of H+ in the oceans causing a decrease in pH. Acidification may lead to the extinction of many marine species.
