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Download Topic 12A: Climate Change, Part I Online Lecture: The Greenhouse
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12A_1 – Slide 1 Topic 12A: Climate Change, Part I Online Lecture: The Greenhouse Effect & Global Warming ○ Climate vs. Weather ○ Electromagnetic Waves and The Greenhouse Effect ○ Global Warming & Carbon Dioxide Climate 12A_1 – Slide 2 – Weather: what will happen today or this afternoon – Climate: conditions will be warm or cool on most days, how much rain will fall during a season ○ Global Warming is an example of Climate Change – more warm days, fewer cool days (every day is not going to be warm) – won’t matter most of the time, but during extreme conditions (e.g., very hot days) the small boost in temperature could have large consequences ○ Climates do not necessarily change slowly. Instead, they often “flip” from one “setting” (e.g., warm) to another “setting” (e.g., cold), like a light switch. – are we destabilizing the nice climate that we have now? The Electromagnetic Spectrum There are many kinds of EM Waves. Each kind behaves differently with matter. Most are invisible to us, but they can still “burn” us. 12A_1 – Slide 3 Gamma Rays X-Rays Ultraviolet “Light” Visible Light Infrared “Light” Microwaves, RADAR TV Radio Objects Emitting EM Waves Objects must be very HOT to emit visible light. 12A_1 – Slide 4 All objects emit infrared “light,” even cold ones. (e.g., dew) Hotter = send away more EM waves (“heat,” energy) Greenhouses & How They Work 12A_1 – Slide 5 walls made of glass Glass lets visible light pass through, but absorbs infrared “light” The warmer the car seat & window get, the more heat they emit (“send away”) as infrared light. ing 2 ibleW v is red a r f in ed r a r inf Car Seat 1 in ds hi eld 3 ed r a r inf 3 Seat gets heat from both Sun & window. Thank You, Greenhouse Effect 12A_1 – Slide 6 ○ Like a window, “greenhouse gases” in the atmosphere let visible light from the Sun pass through. ○ Greenhouse gases absorb infrared “light” emitted by the Earth, so the air becomes warmer. e If there were no “greenhouse effect,” the Earth would be a big ball of ice visibl ○ Once the atmosphere has gotten warm enough, it emits lots of infrared “light” too, sending some off into space and the rest back down to the Earth, warming it. Examples of greenhouse gases? What 2 gases make up 99% of the atmosphere? “Blanket” Atmosphere Global Warming I:Temperature 12A_1 – Slide 7 Global Warming is Happening: an observation How much does ocean temperature change during El Niño’s? Do El Niño’s have a large or small effect on our climate? ≈1900 0.8oC Global Warming II: Melting Ice at the Poles Antarctica North Pole 12A_1 – Slide 8 12A_1 – Slide 9 Global Warming III: More Melting Ice Melting Glaciers Global Warming IV: Sea-Level Rise & More 12A_1 – Slide 10 species behavior (e.g., coming out of hibernation, growing leaves): happening earlier in the spring about 1 ft Coral Atoll: They really notice it. species which prefer “warm” conditions are spreading towards the Poles and up mountains Carbon Dioxide Measurements from Ice Air is trapped in Layers of Ice 12A_1 – Slide 11 Why is the World Getting Warmer? 12A_1 – Slide 12 Confident or not? Why? ○ Current, Best Theory: We are significantly enhancing the GE by burning lots of fossil fuels (like oil & coal) which adds carbon dioxide to the atmosphere. ○ Carbon dioxide in the atmosphere is going up dramatically owing to human activities – up by 30%+ Why does the curve go up and down a little bit each year? Direct Measurements (since 1950s) Carbon Dioxide & Temperature 12A_1 – Slide 13 Temperature & CO2 went up & down together in the past We’ve added the same amount of CO2 that entered the atmosphere at the end of the last ice age. More CO2 when warmer There should be even more of our CO2 in the atmosphere. The ocean absorbs about half (48%) of our pollution.