The first is from the American Scientist:
"The three bars on the left show carbon-dioxide emissions from all sources in 2005; the red bar on the right shows President Obama's total emissions goal for 2050. It will be very difficult to get the 2005 category labeled 'everything else' much below the 2050 goal, implying that the 2050 emissions targets for electricity generation and motor transport must be essentially zero." Good luck with that!
This graph from National Geographic describes 15 "stabilization wedges" to reduce carbon emissions by at least half over the next 50 years. It is based on the work of Princeton Researchers Robert Socolow and Stephen Pacala. (Click on link above for a photo you can enlarge.)
Here is the International Energy Agency's latest (2010) graph of baseline projections (which assumes that governments introduce no new energy or climate policies) and what it calls the "blue scenario" (which sets the goal of halving global energy-related carbon dioxide emissions by 2050, as compared with 2005). The projections are based on what the IEA considers the least-cost means of achieving that goal via existing and new low-carbon technologies.
The following table spells out the IEA assumptions (click to enlarge)
For more graphs and slides from Princeton's Carbon Mitigation Initiative, see here. According to CMI's baseline projection, carbon dioxide emissions are projected to double by 2050, whereas "keeping emissions flat for 50 years will require trimming projected carbon output by roughly 7 billion per year by 2060, keeping a total of 200 billion tons of carbon from entering the atmosphere." CMI believes that there are many strategies "available today that can be scaled up to reduce emissions by at least 1 billion tons of carbon per year by 2060," each of which it calls a "wedge." Eight wedges (out of the potential 15 identified) are needed to keep emissions flat for 50 years.
The 15 wedges are grouped into 8 different categories
Efficiency: 1. Double fuel efficiency of 2 billion cars from 30 to 60 mpg. 2. Decrease the number of car miles traveled by half. 3. Use best efficiency practices in all residential and commercial buildings. 4. Produce current coal-based electricity with twice todays efficiency.
Fuel Switching: 5. Replace 1400 coal electric plants with natural gas-powered facilities.
Carbon Capture and Storage: 6. Capture AND store emissions from 800 coal electric plants. 7. Produce hydrogen from coal at six times today's rate AND store the captured CO2. 8. Capture carbon from 180 coal-to-synfuels plants AND store the CO2.
Nuclear: 9. Add double the current global nuclear capacity to replace coal-based electricity.
Wind: 10. Increase wind electricity capacity by 15 times relative to today, for a total of 2 million large windmills.
Solar: 11. Install 350 times the current capacity of solar electricity. 12. Use 40,000 square kilometers of solar panels (or 4 million windmills) to produce hydrogen for fuel cell cars.
Biomass Fuels: 13. Increase ethanol production 15 times by creating biomass plantations with area equal to 1/6th of world cropland.
Natural Sinks: 14. Eliminate tropical deforestation. 15. Adopt conservation tillage in all agricultural soils worldwide.
The CMI presentation, like the National Geographic graph noted above, can also be divided into four diferent categories:
Joe Romm of Climate Progress argued in 2008 that "probably more than 14 wedges starting in 2010" (rather than the 7--now 8--of Princeton's projection) are needed to stay below 450 ppm, whereas "we currently don't have the political will to do more than 2 or 3." In his 2008 review of Socolow and Pacala's projections (on which the Princeton CMI study is based), Romm noted several problems in their analysis. The following is not a comprehensive list, but among the problems are the following: Emissions have been rising at 3% per year instead of the 1.5% annual emissions growth of the last thirty years assumed in CMI's analysis. Further, "a wedge is a mind-boggingly large amount of 'activity,' with one nuclear wedge requiring 14 new nuclear plants per year for the next 50 years, 7.4 new plants to replace those retired, and 10 Yucca Mountains to store the waste. But if 3% growth if the new norm, you would have to double that to make one wedge. Storing the emissions from 800 large coal plants (four-fifths of those existing in 2000) would require "a flow of CO2 into the ground equal to the current flow of oil out of the ground," necessitating the re-creation "the equivalent of the planet's entire oil delivery infrastructure." One wedge of biofuels would require one-sixth of the world's cropland.
Despite the enormity of these challenges, Romm's basic point is that we need twice the number of wedges called for in CMI's analysis. His latest thoughts ("The Full Global Warming Solution") sees the need for 12-14 wedges.
With progress exceedingly slow on international climate accords, the Republican victory in the 2010 U.S. elections, and the dramatic fall in the market value of solar and wind companies, the probability of action on the scale the climate hawks deem necessary seems to be just about 0.0%. Romm's argument in 2008 that the political will existed for only two or three of the "wedges" seems to have been excessively optimistic. Climate-Lack-of-Progress is looking a lot more like it.