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
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?
Ways to Reduce CO2 Emissions
• Renewable/clean energy• Improved energy efficiency• Carbon capture and storage (CCS)• Reforestation• Active management of forests
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)
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)
Coal Cars, WY (photo by Greg Goebel, http://www.vectorsite.net/Yvcol_2m.jpg)
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