1. Evidence of Global Warming and Consequences1

2. Average Global Temperatures are Rising
Current climate data (past few hundred years) is more accurate due to the technology enabling the collection, but only gives short term information.

3. Greenhouse Gases are Increasing
Direct atmospheric and ice core measurements show greenhouse gas levels have been rising since the 1700s.
This corresponds to the start of the “Industrial Revolution”.

4. Tree Ring Analysis
The growth rings of trees are used to determine relative temperature and amount of rainfall in the years the tree has been living.
Larger spaces between rings shows warmer, wetter years.
Small spaces between rings could mean warm, but dry or could simply mean cool conditions for that year. 4

5. Sedimentary Rock Analysis
The layers of rock sediments in the Earth and their composition provide insight into former climates.
Carbon isotopes are used to date the age of the sediments, as well as indicate how much carbon was being cycled in the world (evidence of higher global temperatures) at those times.
This can go back millions of years.
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6. Global Temperature Changes
Earth’s temperatures have fluctuated.
Scientists do not fully understand all the reasons behind the warming and cooling periods of the Earth.
Climate data a very long time ago provides a broader view of the climate history of the Earth, but can only be obtained through methods of inference. 6

7. Global Consequences
A positive feedback loop is a sequence of events that cycles back to enhance an outcome.
One major concern is that the impacts of climate change will further enhance the process.

8. Deforestation Feedback Loop
Forests are important carbon sinks.
Absorb CO2 and convert it into sugar by photosynthesis:
6CO H2O C6H12O O2
sugar
Logging and agriculture reduce global forests. Climate change may speed this up.

10. Albedo Feedback Loop
Albedo: measures the amount of light reflected by an object.
Clouds and ice have a high albedo - they reflect, not absorb, sunlight.
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12. “Soda Pop” Feedback Loop Analogy…for CO2
A warm bottle of pop is more “fizzy” than a cold one…
Carbonated beverages contain dissolved CO2
At high temperature, less CO2 can dissolve in the pop.
When the pop is opened, CO2 begins to escape by forming bubbles.

14. Negative Feedback Loops
Negative feedback loops exist too:
Higher temperatures and more CO2 may stimulate photosynthesis, decreasing CO2.
Increased evaporation due to global warming may cause more cloud formation, resulting in a higher global albedo and global cooling.

15. Global Warming vs. Climate Change
Video is just over 6 min long. 15