1. 21.3 Climate Changes Objectives
Describe natural processes that can cause changes in climate.
Explain the greenhouse effect
Define global warming
List some of the consequences of global warming
Bill Nye explains Climate Change

2. Natural Processes That Change Climates
 Volcanic Eruptions
• Volcanic particles in the air increases amount of solar radiation reflected back into space. Causes Earth’s lower atm. to cool.
Fig. 14 pg. 600 Eruption of Mount Pinatubo
Example: Mount Tambora in 1815 erupted in in Indonesia. The next year (1816) is known as the year without a summer and there was crop failure in Europe. It snowed in July!

3. Ocean circulation
El Niño causes parts of the eastern tropical Pacific Ocean to become warmer than usual.
New ocean currents also form as a result of plate tectonics
Will learn more about El Nino next unit!

4.  Solar Activity: Recently one of the most studied hypothesis for the causes of climate change are based on solar energy output.
• When sun is most active, it contains dark blemishes called sunspots.
Formation of sunspots appeared to correspond with warm periods in Europe & North America.
Further evidence has suggested that the correlation was coincidental, but obviously the stability of our climate is dependent on solar output to a certain extent and the topic cannot be dropped all together!

5.  Earth Motions: LONG-TERM CHANGES IN CLIMATE
• Changes in shape of Earth’s orbit & tilt also affect climates.
• Geographic changes in Earth’s land & water bodies cause changes in climate (like plate tectonics, uplift, formation of mountains).
This refers to plate tectonics, and the precession of Earth’s orbit

6. Human Impact on Climate Changes
 The Greenhouse Effect
• Natural warming of Earth’s lower atm. & surface from radiation being absorbed & emitted by greenhouse gases.
I compare to blankets on a cold night. You need a couple to stay alive, but you could also pile on so many blankets that you end up sweating!
The major gases involved are water vapor and carbon dioxide, help maintain warm temperatures in the lower atmosphere = can support life
The greenhouse effect is necessary for life, but you can certainly have too much of a good thing!

7.  Global Warming
• Increase in global temperatures as a result of increased levels of carbon dioxide & other greenhouse gases.

8. Coincidence?
Makes no sense without caption in book

9. How scientists predict global warming
Climate Models (approximation): complex computer programs using data to predict how temperature increases could affect Earth
Fig. 17: Increases in Greenhouse Gases and Changes in Temperature

10. What can happen… Warmer surface temps increase evaporation rates
This increases the amount of water vapor in the atmosphere
Water vapor absorbs solar radiation emitted by Earth and causes sea ice to melt
Retreat of Helheim Glacier

11. Ice reflects more incoming solar radiation
So now with ice melting there is more water, and water absorbs the solar energy
This will magnify the temp increase created by higher levels of greenhouse gases

12. -More shoreline erosion and coastal flooding
-Melting of ice will cause a global rise in sea levels
-More shoreline erosion and coastal flooding

13. Swimsuit Evidence for Global Warming!

14. 21.3 REVIEW
Describe 4 natural processes that can cause climate change.
Volcanic eruptions – ash can trap heat and radiate it back to space
Ocean circulation patterns – can change atmospheric circulation (e.g., El Nino)
Solar activity – can change global temperature
Earth motions – tectonism & revolution

15. 21.3 REVIEW What is global warming?
The increase in global temperatures, due to increase levels of greenhouse gases

16. 21.3 REVIEW How might global warming affect Earth’s inhabitants?
Global warming could:
Harm or kill ocean organisms
Cause land and water habitats to shift or be destroyed
Increase spread of disease
Increase drought, flooding and heat waves
Etc.