1. Climatic Changes

2. Causes of Climate (Review)
Latitude – differential heating
Topographic effects –
Proximity to water
Altitude
Mountain range
Air Masses

3. Climatic Changes

4. Short-term climatic changes
1. Seasons due to Earth’s tilt on its axis
2. Volcanism
3. Albedo – reflectivity of surface
4. El Nino
5. Solar activity (sunspots)
6. Earth’s wobble (every 26,000 yrs)
7. Earth’s orbit (changes every 100,000 yrs) & tilt (every 41,000 yrs)
8. Atmospheric composition (human induced CO2)

5. 1. Seasons What causes them?
The tilt of the earth on its axis. Seasons are NOT caused by distance from the sun.
The hemisphere tilted toward the sun receives more direct radiation. How does this affect intensity?

6. 2. Volcanic activity
Big eruptions send a massive amount of dust in the atmosphere. It can remain suspended for years blocking solar radiation.
IR from Earth is able to pass through clouds, dust and gas
Cause cooler climate periods
Short term climate change

7. 4. El Nino
Climate changes due to reversing of an ocean current in the Pacific Ocean.
Basically, El Nino can flip climate conditions in many areas.

8. 5. Solar activity
Relationship between low sunspot activity and colder climates on earth.
Maunder Minimum – low sunspot activity period
More sunspots deliver more E to Earth’s atm so global temps rise
Even though sunspots are cooler than normal
According to current theory, sunspots occur in pairs as magnetic disturbances in the convective plasma near the Sun's surface. Magnetic field lines emerge from one sunspot and re-enter at the other spot. Also, there are more sunspots during periods of increased magnetic activity. At that time more highly charged particles are emitted from the solar surface, and the Sun emits more UV and visible radiation.

9. 6. Earth’s wobble
The axis of the earth points to a different point every years.
Switches cause summer and winter to be more drastic, because the earth will be closer to the Sun during summer and farther away during winter.

10. 7a. Earth’s orbit
Earth’s orbit cycles between circular and elliptical every 100,000 years.
A more elliptical orbit = warmer climate because earth is closer to the sun.

11. 7b. Earth’s tilt
Currently the earth has a 23.5 degree tilt on its axis. Seasons are caused by the tilt changing throughout the year.
The angle varies from 22.1º to 24.5º every 41,000 years.
Less angle = seasons not as drastic (milder winter, cooler summer)

12. 8. Atmospheric Composition
Concentration of greenhouse gases, particularly CO2, is important in global climate regulation
These gases trap heat inside earth’s atmosphere
Human influence causes short-term or long-term climate change?
What does the amount of carbon dioxide have to do with climate?

13. Greenhouse effect video clip
Greenhouse effect – natural heating of earth’s surface caused by certain atmospheric gases (water vapor, carbon dioxide).
The gases trap heat that is radiated by the earth.
It is NOT a human invention.
It may be possible to increase or decrease the greenhouse effect by changing the amount of greenhouse gases (CO2)
This is the current controversy

16. The “Greenhouse Effect”
The Earth’s surface thus receives energy from two sources: the sun & the atmosphere
As a result the Earth’s surface is ~33C warmer than it would be without an atmosphere
Greenhouse gases are transparent to shortwave but absorb longwave radiation
Thus the atmosphere stores energy

18. Other planets also have Greenhouse Effects,
but these are unsuitable for life
Venus
Atmosphere: mass 90x earth’s
GH Gases: >90% CO2
Sfc. Temp.: C
GH Effect: C
FAR TOO HOT!
Sun
Earth
GH Gases: ~0.04% CO2
~ 1% H2O
Sfc. Temp.: C
GH Effect: C
NOT BAD!
Although the high surface temperatures on Venus are partly attributable to its closer proximity to the sun, a primary reason is the strong greenhouse effect induced by a dense atmosphere almost entirely made up of carbon dioxide.
In contrast, Mars is cold because it is farther from the sun than earth and has a very thin atmosphere. Despite the high CO2 concentration, the net greenhouse effect is much weaker than for earth.
Reference:
IPCC Climate Change: The IPCC Scientific Assessment [Houghton,J.T. et al. (eds.)]. Cambridge University Press, Cambridge, UK. pg. Xxxvii
Images: NASA
Mars
Atmosphere: mass <1% earth’s
GH Gases: >80% CO2
Sfc. Temp.: C
GH Effect: C
FAR TOO COLD!

19. Atmospheric CO2 Data
Direct Measurements, Hawaii
Evidence

20. Ice Core CO2 Data

22. Global Warming
Temps have warmed over the last 200 yrs (scientists agree)
Could eventually cause ice caps to melt, coastal flooding, deserts to spread, and more severe storms
More…
EPA…

23. Global Warming, pg 376!!! Scientists agree that temps are climbing
Do not all agree about why
Natural vs artificial (human) influences increasing CO2 in the atmosphere

24. The CO2 Cycle
Natural process
Sources: volcanism, metamorphism, respiration, fossil fuel burning, deforestation
Sinks: photosynthesis, rock weathering, carbonate depsoition, ocean adsorption

25. The CO2 Cycle as Earth’s Thermostat
Increased volcanism inputs huge quantities of CO2 into the atmosphere = T° increases
T° increase causes increased chemical weathering and marine carbonate deposition which lowers atmospheric CO2

26. The CO2 Cycle as Earth’s Thermostat
Feedback is not instantaneous! Perturbations in CO2 cycle take on the order of 500,000 years to restore.

27. Increase of carbon dioxide
Burning of fossil fuels
Deforestation
How can we help?!?!
Artificial

28. Renewable vs. Nonrenewable
Renewable energy sources – energy from resources that are continually replenished
Examples?
Nonrenewable energy sources – take thousands of years to form. Cannot be replaced as quickly as they are used
Compare and contrast benefits?

29. Renewable Energy
Nonrenewable Energy