Transcript Slide 1
Global Warming: Fact, Fiction, and Best Estimates By Scott Hewitt Dept. of Chemistry & Biochemistry California State University, Fullerton Global Warming Teach-In Cal. State Fullerton What is the greenhouse effect? Does the greenhouse effect really exist? • Without the greenhouse effect, the average temperature on Earth would be about -2 oF. • The average global temperature is 59 oF. • Yes, the greenhouse effect really does exist. Is global warming really occurring? But in some parts of the world, it is very cold this winter? • Regional weather fluctuates • “Global warming” refers to the Earth’s temperature, averaged over the entire planet and the entire year – not to the temperature at one location or at one time. • Even the average global temperature will fluctuate, as it is based on so many variables. Is the global warming due to greenhouse gases? Is the global warming due to greenhouse gases? Is the global warming due to greenhouse gases? • The average global temperature is increasing as greenhouse gas concentrations rise. • Climate models cannot reproduce the observed temperature trend without including the rise in greenhouse gases. • Yes, it appears that global warming is mainly caused by the rise in greenhouse gases (IPCC: 90% certainty). Or, is global warming due to the sun? • Since 1750, the average amount of energy coming from the sun has stay fairly constant, but has increased a little. • If a more active sun were the cause of global warming, we would expect warming in all layers of atmosphere. • However, the upper atmosphere has cooled due to greenhouse gases trapping of heat in the lower atmosphere. • It appears that solar radiation only plays a small part in global warming (no more than 10%). What other evidence supports the idea that global warming is occurring? Muir Glacier, Alaska, Aug. 1941 • EMS outbreak affected 1500 people who had be administered a pharmaceutical tryptophan solution. • 27 people died. Bruce Molnia, USGS Muir Glacier, Alaska, Aug. 2004 vious Tryptophan Degradation Studies gradation products detected vary widely depending on nditions and instrumentation used. treme conditions used: • High concentrations • Non-natural oxidation systems • Greater than 40% loss of tryptophan PLC, GC-MS, and TLC used previous studies of commercial amino acid solutions. Bruce Molnia, USGS Extent of Arctic Sea Ice Magenta line • median Sept. 1979 - 2000 White area • Sept. 9, 2007 National Snow & Ice Data Center Ice Mass Greenland Meltwater Snowcap/Glacier on Mt. Kilimanjaro Sea Level Rise Why should we care about global warming? I like the heat. • Flooding of coastal areas • Changes in regional weather (hurricanes, floods, droughts, heat waves, fires) • Geographic shift in flora and fauna (loss of biodiversity, loss of agricultural productivity, more infectious diseases, loss of fishing stock) • Economic loss (national security issue) How much warming will occur by 2100? • The IPCC predicts warming of 2 to 10 oF over the next century. • There is significant uncertainty in these numbers. What is the “tipping point”? • When greenhouse gas emissions rise high enough that “runaway” global warming occurs due to ... • snow absorbs less sunlight than land • methane burp when the frozen tundra thaws • when positive feedback loops overwhelm the climate system (i.e., when global warming causes more global warming, which causes more global warming, …) What do we need to do to protect ourselves? • Limit CO2 levels to 450 ppm, reduce greenhouse gas emissions 60-80% by 2100 (Jim Hansen, 2006) • Reduce greenhouse gas emissions 80% by 2050 (Barack Obama, 2008) • Reduce CO2 levels to 350 ppm (Jim Hansen, 2009) • As to where the tipping point is or as to how much we need to reduce greenhouse gas emissions, we can only estimate • However, what is becoming clear is that we need to act soon. Tomorrow, what will you do to build a sustainable future? Acknowledgements • Marlene Nang • Dr. Jason Hamilton, Ithaca College • www.noaa.gov • www.jpl.nasa.gov • CSUF faculty, staff, students, and administrators My contact info: [email protected]