1. The Controversy • Basic temperature and CO2 data are not in dispute • Controversy focuses on whether or not warming trend is anthropogenic • Earth’s temperature has fluctuated in the past • Could be part of a natural cycle • Warming may not be caused by CO2 • Vast majority of climate scientists believe anthropogenic contribution to temperature increase is substantial

2. Some Potential Consequences of Global Warming in 21st Century • Melting of glaciers and sea ice • Sea level rise (1.5 – 6.5 ft) • Major shifts in precipitation • Increased extreme weather events • Large floods • Greater storm intensity • Large fires So, what can be done?

3. Ways to Reduce CO2 Emissions • Renewable/clean energy • Improved energy efficiency • Carbon capture and storage (CCS) • Reforestation • Active management of forests

4. Stabilization Wedges • Each wedge ~1 Gigaton C per year by 2054 • Possible wedges are: • Improved fuel efficiency (60 mpg cars) • Energy efficient buildings • Nuclear power • Alternative energy sources • CCS Pacala & Socolow (2004)

5. How much is a Gigaton of carbon? 1 billion tons Coal 78% C Each boxcar ~ 100 tons coal 1 GtC = 12 million boxcars coal Enough boxcars to extend ~5 times around Earth Coal Cars, WY (photo by Greg Goebel, http://www.vectorsite.net/Yvcol_2m.jpg)

6. Tons of CO2 per ton of coal burned? Atomic wt C = 12, O = 16 1 ton C produces 3.66 tons CO2 Coal 78% C 1 ton coal produces 2.86 tons CO2 Coal Cars, WY (photo by Greg Goebel, http://www.vectorsite.net/Yvcol_2m.jpg)