1. The Controversy Basic temperature and CO 2 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 CO 2 Vast majority of climate scientists believe anthropogenic contribution to temperature increase is substantial

2. Some Potential Consequences of Global Warming in 21 st 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 CO 2 per ton of coal burned? Atomic wt C = 12, O = 16 1 ton C produces 3.66 tons CO 2 Coal 78% C 1 ton coal produces 2.86 tons CO 2