1. Ch16: Global Warming-part 1 What is it? What causes it? Focus on Carbon Dioxide

2. Global Warming What is it? Global warming (GW): the unprecedented increase in the temperature (Figs 16.1 and 16.2) of the earth's atmosphere over the last 100 years. The earth's temperature has increased 1 o F or 0.5 o C since 1900 and the increase has accelerated in the last 20 years.

5. Impact of Global Warming (Evidence) Shorter winters Rise in sea level Changes in precipitation (Fig 16.3) Changes in crop distribution Changes in animal, plant and microorganism habitat and viability Melting of polar ice caps, glaciers

7. Global Warming What causes it? The sun drives the earth's climate. It heats the earth with infrared (IR) radiation (0.75-4  m). Some of that thermal IR energy (0.75- 50  m) is reflected back into the atm. –some reflected IR escapes the earth's atm. –some reflected IR is absorbed by molecules and converted to heat. This keeps the earth's temp at a livable +15 o C (vs -15 o C). The role of these molecules in maintaining the temp balance on earth is called the greenhouse effect.

8. GW: What Causes It? However, increased levels of greenhouse gases can prevent too much IR energy from escaping the earth's surface causing the surface to warm up even more (enhanced greenhouse effect). The most common greenhouse gases are H 2 O, CO 2 (+30% increase in atm over last 150 years), CH 4 (+50%), N 2 O (+15%), O 3.

9. GW: What Causes It? Focus on CO 2 CO 2 absorbs reflective IR radiation at 15  m and produces heat. This decreases the amount of reflective IR radiation that can leave the earth's atm (Fig 16.7) Other greenhouse gases absorb IR radiation at other wavelengths. Note ozone absorption at 9  m within atmospheric window

11. Atmospheric CO 2 Analysis of glacier bubbles in Antarctica and Greenland show that – CO 2 levels increased dramatically in 1750 (Industrial Revolution). –Figs 16.8 and 16.9 show the even larger increase in atm CO 2 since 1950. Natural CO 2 Sources –Decay and combustion of plant material

12. Atmospheric CO 2 Anthropogenic CO 2 sources account for most of increased atm CO 2 levels –Burning of fossil fuel 98% of US CO 2 emission almost 75% of worldwide CO 2 emission CH 4 +2O 2  CO 2 + H 2 O –Deforestation accounts for about 25% of worldwide CO 2 emission –CaCO 3 (limestone) + heat  CaO (lime) + CO 2

15. CO 2 Dissolved in Oceans "The Dangers of Ocean Acidification", Scientific American, March 2005, pp58-65 http://yosemite.epa.gov/oar/globalwarming. nsf/content/impacts.htmlhttp://yosemite.epa.gov/oar/globalwarming. nsf/content/impacts.html