1. Warm-Up Word Splash- Take a few minutes to think about the following words and tell me what they mean to you. Global Warming Climate Change

2. Essential Question How does the composition of the atmosphere affect the temperature of the Earth?

3. What’s the difference between “global warming” and “climate change”?

4. Difference GLOBAL WARMING is the increase of the Earth’s average surface temperature due to a build-up of greenhouse gases in the atmosphere. CLIMATE CHANGE is a broader term that refers to long- term changes in climate, including average temperature and precipitation.

5. Review from yesterday…  Why is it that we need an atmosphere?

6. First we need to look at the what is the atmosphere!  The atmosphere is a thin layer of gases that surrounds our Earth.  Without the atmosphere, organisms that survive on Oxygen would not be able to survive.  This atmosphere also helps to distribute the heat gained from the sun’s rays.

7. Composition of the Atmosphere  The atmosphere consists of  78% N2  21% O2  1% Ar  And other trace amounts of permanent gases

8. Our Climate’s History  Since the time of Earth’s existence, the atmosphere has changed. Its composition began primarily as hydrogen and helium. As Earth processes took place – such as volcanic eruptions, the atmosphere began to change. It is hypothesized that Earth’s atmosphere was very similar to Venus’ atmosphere – primarily CO2, which made the Earth an unbearable place to live.

9. First Atmosphere  Composition - Probably H 2, He  These gases are relatively rare on Earth compared to other places in the universe and were probably lost to space early in Earth's history because  Earth's gravity is not strong enough to hold lighter gases  Earth still did not have a differentiated core (solid inner/liquid outer core) which creates Earth's magnetic field which deflects solar winds.  Once the core differentiated the heavier gases could be retained

10. Second Atmosphere  Produced by volcanic out gassing. Gases produced were probably similar to those created by modern volcanoes (H 2 O, CO 2, SO 2, CO, S 2, Cl 2, N 2, H 2 ) and NH 3 (ammonia) and CH 4 (methane)  No free O 2 at this time (not found in volcanic gases).  Ocean Formation - As the Earth cooled, H 2 O produced by out gassing could exist as liquid in the Early Archean, allowing oceans to form.  Evidence - pillow basalts, deep marine beds in greenstone belts.

12. Addition of O 2 to the Atmosphere  Today, the atmosphere is ~21% free oxygen.  Oxygen Production  Photochemical dissociation - breakup of water molecules by ultraviolet  Produced O 2 levels approx. 1-2% current levels  At these levels O 3 (Ozone) can form to shield Earth surface from UV  Photosynthesis - CO 2 + H 2 O + sunlight = organic compounds + O 2 - produced by cyanobacteria, and eventually higher plants - supplied the rest of O 2 to atmosphere. Thus plant populations  Oxygen Consumers  Chemical Weathering - through oxidation of surface materials (early consumer)  Animal Respiration (much later)  Burning of Fossil Fuels (much, much later)  During the Proterozoic the amount of free O 2 in the atmosphere rose from 1 - 10 %. Most of this was released by cyanobacteria, which increase in abundance in the fossil record 2.3 Ga. Present levels of O 2 were probably not achieved until ~400 Ma.

13.  Life on Earth is supported by the atmosphere, solar energy, and our planet's magnetic fields.  The atmosphere absorbs the energy from the Sun  Recycles water and other chemicals  Works with the electrical and magnetic forces to provide a moderate climate.  Protects us from high-energy radiation and the frigid vacuum of space. Benefits of Our Atmosphere

16. Earth Naturally goes through a warming and cooling periods….  Serbian astronomer Milutin Milankovitch, who calculated the slow changes in the earth's orbit by careful measurements of the position of the stars, and through equations using the gravitational pull of other planets and stars.  The Milankovitch or astronomical theory of climate change is an explanation for changes in the seasons which result from changes in the earth's orbit around the sun.

17. What does this mean?  The combination of the 41,000 year tilt cycle and the 22,000 year precession cycles, plus the smaller eccentricity signal, affect the relative severity of summer and winter, and are thought to control the growth and retreat of ice sheets.  Cool summers in the northern hemisphere, where most of the earth's land mass is located, appear to allow snow and ice to persist to the next winter, allowing the development of large ice sheets over hundreds to thousands of years.

19. Earth’s Natural Greenhouse Effect  Greenhouse gases like water vapor, carbon dioxide, methane and nitrous oxide trap the infrared radiation released by the Earth's surface.  The atmosphere acts like the glass in a greenhouse, allowing much of the shortwave solar radiation to travel through unimpeded, but trapping a lot of the longwave heat energy trying to escape back to space. This process makes the temperature rise in the atmosphere just as it does in the greenhouse. This is the Earth's natural greenhouse effect and keeps the Earth 33°C warmer than it would be without an atmosphere, at an average 15°C.

20. The Sun’s energy passes through the car’s windshield. This energy (heat) is trapped inside the car and cannot pass back through the windshield, causing the inside of the car to warm up. Example of the Greenhouse Effect

21. A Global Warning?  Complete questions as the movie goes- if you can not answer them as you watch, you need to answer them when it is over. I will be collecting this!