1. Climate Change – Examining the Evidence
Chapter 3

2. Objectives describe the composition of greenhouse gases
relate incidence of greenhouse gases to human activity
describe the relationship between greenhouse gases and climate change
discuss international collaboration on climate change, including specific programs
assess the impacts of climate change

3. Greenhouse Gases
Natural greenhouse effect  keeps planet warm by absorbing some of the thermal energy radiated from the Earth
Caused mainly by water vapor
Four main greenhouse gases:
Water vapor
CO2
Methane
Nitrous oxide (N2O)

4. Global Warming Potential
Gas
Global Warming Potential
Persistence (years)
Carbon dioxide 1
50-200
Methane 23 10
Nitrous oxide (N2O)
296
120
Global warming potential  measure of ability of gas to trap thermal energy
 CO2 most common; everything measured against it
Persistence  time gas remains in atmosphere

5. Enhanced Greenhouse Effect
There is a necessary amount of global warming that makes our planet inhabitable.
Current global average:
15°C
With no carbon dioxide or water vapor in the air:
-18°C

6. Enhanced Greenhouse Effect
This enhanced greenhouse effect is referring to the greater amount of carbon (in the form of CO2 ) that is being put into the atmosphere.

7. Enhanced Greenhouse Effect
Water vapour is one of the natural green house gases present in the atmosphere.
Water vapour lasts about 10 days in the atmosphere before falling as precipitation.

8. Enhanced Greenhouse Effect
Water vapour may only last 10 days in the atmosphere but it makes up 65% of the greenhouse gases.
With enhanced global warming there might be more evaporation of water.

9. Enhanced Greenhouse Effect
All of the greenhouse gases differ in many different ways:
Their global warming potential
Their length of time in the atmosphere
Rate of addition to the atmosphere.
Effect on other gases in the atmosphere.

10. Carbon and Carbon Dioxide
Carbon is found in a variety of forms on the planet.
Carbon dioxide in the atmosphere
Carbonates in rocks
Carbon in fossil fuels, and natural gas
In organisms as carbohydrates, lipids, proteins

11. Carbon and Carbon Dioxide
The movement of Carbon through the biosphere is referred to as the carbon cycle.
Each year about 158 Gigatonnes of carbon move through the biosphere
1 Gt = 1,000,000,000 tonnes

12. Increasing CO2 in the Atmosphere
The ice core findings we discussed revealed levels of carbon dioxide that were extraordinarily high.
Since the 1960s CO2 in the atmosphere has gone up from 320 ppm to 390 ppm now.

13. Increasing CO2 in the Atmosphere
The main reason for this increase is the burning of fossil fuels, and the removal of trees.
Carbon sinks are large storage places for carbon compounds.
Rocks and oceans are the largest sinks.
Why are humans continuing to do these things if there is an increase in CO2?

14. Plants and CO2
The presence of large amounts of plants can help reduce the amount of CO2
During photosynthesis CO2 combines with water to make sugars.
Deforestation has a large effect on the amount of CO2 present.

15. Other Greenhouse Gases
Heat Trapping Ability to CO2
Atmospheric life span (years)
Concentration in PPM
2012
Contribution to global warming
Origin
CO2 1
2 – 3
280
390
60%
Mostly human
Methane (CH4) 23 8
0.7
1.76
20%
Natural and human
Dinitrogen monoxide (N2O
296
120
0.275
0.316 6%
CFCs
12400 50 4%
Human

16. Greenhouse Gases
See that concentrations of greenhouse gases in ice cores have increased since about 1700
What historical event occurred then?
Industrial Revolution  increase in fossil fuel consumption
What is a fossil fuel?
Fuel with lots of carbon, formed from living organism remains
Coal, oil and natural gas
Releases all three greenhouse gases

17. Greenhouse Gases and Human Activity
What does this mean overall?
Increased greenhouse gas levels mean that less thermal energy is released back into space
Average temperature of Earth rises

18. Carbon Sources and Sinks
Carbon source  process releasing CO2(g) to atmosphere
Includes burning fossil fuels and respiration
Carbon sink  removes CO2(g) from the atmosphere
Photosynthesis
Dissolved CO2(g) in oceans and lakes
How are we increasing CO2(g) in the atmosphere?
Forest removal
Agriculture
Garbage (releases nitrous oxide)

19. Halocarbons Human-made chemicals
Absorb significant amounts of thermal energy
Used as coolants
Fridges, air conditioners
CFCs  class of halocarbons
Global warming potential of
Used to be in aerosols
Restricted use
Contribute to the destruction of ozone
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20. Greenhouse Effect and Climate Change
What is the greenhouse effect?
Global warming  observed increase in Earth’s average temperature
Important detection organization:
IPCC (Intergovernmental Panel on Climate Change)
Operates out of UN
If we continue with our current practices, global warming will continue and result in climate change

21. Other Evidence Flowers in Northern Hemisphere blooming 26 days earlier
Severe weather-related disasters
Amount of snow cover and ice has decreased
Level of oceans increased 2-5 cm

22. Evaluating Evidence of Climate Change
Study of climate change challenging
Confidence rating  probability that result is true
Analyses and predictions have higher confidence ratings with
More data
More accurate measurements
Good understanding of factors involved
Ex. Have high confidence rating for increasing greenhouse gases