The Future. Stabilizing atmospheric CO 2 at ~ 500ppm. Paths to CO 2 stabilization. Climate Stabilization: The Pacala & Socolow analysis

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1 Week 10 (the last week) Today: Mitigation (cont) Tuesday: Geo-engineering Wed: Media reports/class evaluation Thur: Summary of class Thur/Fri sections: HW/review/TA evaluation Reminders: CLUE session on Tue 8pm & Wed at 6:30-8:00pm HW #6 due on Thursday Final Exam on Monday Dec 8th 8:30-10:20am (here) More info on Wednesday Help session on Sunday evening (TBA) The Future What do we have to do to global? What does this imply for US? Alternatives to reduced : geoengineering The Future What do we have to do to global? What does this imply for US? Emissions How much Carbon Dioxide will be released into the atmosphere? B1 (utopia) A2 (business as usual) A1B A2 A1B B1 Alternatives to reduced : geoengineering Estimates depend on population and economic projections, future choices for energy, governance/policy options in development (e.g., regional vs. global governance) Global Annual Average Surface Temperature Model Uncertainty Reminder: more than CO 2 contributes to warming Usually convert other gases to an equivalent mass of CO 2 that would cause the same forcing Amount shown is emitted (equivalent) CO 2 To get emitted equivalent C, multiply by 12/44 Referenced to the Average Temperature Solid lines: average of all models used. Number of models used varies; shaded area is the standard deviation of the models IPCC AR4, Fig 10.4

2 Paths to CO 2 stabilization Paths to CO 2 stabilization: emission reduction requirements by 2050 VI V < At stabilization > <--- Required Action ---> IV II I To achieve stabilization of CO 2 at ~ 500 ppm, global will have to be level or even decrease over the next 40 years, while population increases by 50% and developing countries develop (and thus energy demand increases 0%) IPCC 200 WG III Table SPM.5 Stabilizing atmospheric CO 2 at ~500ppm Stabilizing CO 2 at 500ppm (550 CO 2 equivalent) means that the global averaged temperature will increase by ~3 C High latitudes will warm more than tropics, subtropics will be drier by about 20%, etc. Not exactly the change in temperature at 500ppm, but close enough. The Future What do we have to do to global? What does this imply for US? Alternatives to reduced : geoengineering Climate : The Pacala & Socolow analysis How do we avoid exceding 500ppm of CO 2? on the one hand... IPCC (2001, WGIII): "technologies that exist in operation or pilot stages today" are sufficient to follow a less-than-doubling trajectory "over the next hundred years or more". on the other hand... Hoffert et al. (Science, 2002) claim that the IPCC analysis involves "misperceptions of technological readiness". They call, instead, for "revolutionary changes" in energy technology. Pacala and Socolow argue... Basic research is needed to develop the revolutionary technologies needed for the 2nd half of this century and beyond. Meanwhile, we must (and can) start to solve the carbon/climate problem in the first half of the century "simply by scaling up what we already know how to do.", Science 305, Stabilizing atmospheric CO 2 at ~ 500ppm In 2004, Pacala and Socolow proposed a scheme to achieve this goal Phase 1: Requires immediate cap on global CO 2 and that economic growth over the next 50 years be achieved by ramping up (scaling up) existing technologies without increasing CO 2 Phase 2: After 2054, requires rapid and substantial reductions in global. Final of all GH gases must level off by ~2100 to ~ 1.5 Gt/yr, or ~20% of present global At that time, the ocean uptake will balance the human input (and the ocean will continue to acidify).

3 Billion of Tons of Carbon Emitted per Year Past Emissions The Emission Triangle Billion of Tons of Carbon Emitted per Year Triangle Currently projected path = ramp Flat path O (530) (40) Interim Goal Values in parentheses are ppm (1 ppm = 2.1 GtC) Interim 2054 goal: stabilize immediately (yet increase energy by ~0% in 2054) and invest in technology to have much more energy with reduced after that GtC/yr 1.5 The Triangle: settle for double or triple pre-industrial CO 2? Ramp = Delay Flat = Act Now Business As Usual (530) (50) triangle (40)! 500 ppm (830)! 850 ppm Billion of Tons of Carbon Emitted per Year Wedges Currently projected path Flat path O GtC/y Seven wedges GtC/y Values in parentheses are ppm (1 ppm = 2.1 GtC). Stabilizing at 500ppm requires the global emission be 1.5 Gt/yr How do we meet the increase in energy demand (projected to increase by 0% by 2050 and 200+% by 2100) without increasing of CO 2? What is a Wedge? A wedge is a strategy to reduce carbon that grows in 50 years from zero to 1.0 GtC/yr. The strategy has already been commercialized at scale somewhere. The Interim Goal is Within Reach Reasons for optimism that global in 2055 need not exceed today s : Total = 25 Gigatons carbon 50 years 1 GtC/yr The world today has a terribly inefficient energy system. Carbon have just begun to be priced. Most of the 2055 physical plant is not yet built Cumulatively, a wedge redirects the flow of 25 GtC in its first 50 years. This would cost $1.25 trillion at $50/tC. A $50/tC tax or carbon trading value would raise electricity prices by almost 1 cent per kwh ( ~ 10%).

4 Fill the Triangle with Seven Wedges (~double the energy available in 2054 w/o increasing ) Energy Efficiency Methane Management GtC/y Triangle Forests & Soils GtC/y Nuclear Electricity Effort needed by 2055 for 1 wedge: 00 GW (twice current capacity) displacing coal power. Decarbonized Electricity Decarbonized Fuels Fuel Displacement by Low-Carbon Electricity Phase out of nuclear power creates the need for another half wedge. Graphic courtesy of NRC Wind Electricity Pholtovoltaic Power Effort needed by 2055 for 1 wedge: One million 2-MW windmills displacing coal power. Today: 50,000 MW (1/40) Effort Needed by 2055 for one wedge: 2000 GWpeak (00 times current capacity) 2 million hectares Solar thermal power via concentrators (troughs and dishes) is produced at high efficiency, like PV. Prototype of 80 m tall Nordex 2,5 MW wind turbine located in Grevenbroich, Germany (Danish Wind Industry Association) Power with Carbon Capture and Storage Graphics courtesy of DOE Office of Fossil Energy Effort needed by 2055 for 1 wedge: Carbon capture and storage at 800 GW coal power plants. Graphics courtesy of DOE Photovoltaics Program Lots of potential for increased efficiency in US

5 Efficient Use of Electricity industry Efficient Use of Fuel power buildings Effort needed by 2055 for 1 wedge: Effort needed by 2055 for 1 wedge: 2 billion cars driven 10,000 miles per year at 60 mpg instead of 30 mpg.. 2 billion cars driven, at 30 mpg, 5,000 instead of 10,000 miles per year. 25% - 50% reduction in expected 2055 electricity use in commercial and residential buildings Biofuels Coal-based Synfuels with CCS* *Carbon capture and storage Effort needed by 2055 for 1 wedge: Effort needed for 1 wedge by billion 60 mpge cars running on biofuels instead of gasoline and diesel. Capture and storage of the CO2 byproduct at plants producing 30 million barrels per day of coal-based synfuels To produce these biofuels: 250 million hectares of high-yield (15 t/ha) crops, one sixth of world cropland. Assumption: half of C originally in the coal is available for capture, half goes into synfuels. Graphics courtesy of DOE Office of Fossil Energy Challenge: To find ecologically responsible ways to grow biomass for power and fuel on hundreds of millions of hectares. Result: Coal-based synfuels have no worse CO2 than petroleum fuels, instead of doubled. Need ~1000 times today s capacity Do wedge strategies get used up? For any strategy, is the second wedge easier or harder to achieve than the first? Are the first million two-megawatt wind turbines more expensive or cheaper than the second million two-megawatt wind turbines? The first million will be built at the more favorable sites. But the second million will benefit from the learning acquired building the first million. The question generalizes to almost all the wedge strategies: Geological storage capacity for CO2, land for biomass, river valleys for hydropower, uranium ore for nuclear power, semiconductor materials for photovoltaic collectors. Usina Santa Elisa mill in Sertaozinho, Brazil ( Summary: What s appealing stabilization wedges? The stabilization triangle: Does not concede doubling is inevitable. Shortens the time frame to within business horizons. The wedge: Decomposes a heroic challenge (the Triangle) into a limited set of monumental tasks. Establishes a unit of action that permits quantitative discussion of cost, pace, risk. Establishes a unit of action that facilitates quantitative comparisons and trade-offs. The wedge strategy: Does not change the fact there are winners (alternative energies) and losers (coal and oil become more expensive sources of energy).

6 The Future What do we have to do to global? What does it mean for US? What does this imply for US? Alternatives to reduced : geoengineering Phase II ( ): drastic reductions in global (while increasing energy) 21 GtC/yr 1.5 Ramp = Delay Flat = Act Now Business As Usual (530) (50) triangle (40)! 500 ppm ! 850 ppm Values in parentheses are ppm (1 ppm = 2.1 GtC) Stabilizing at 500ppm requires the global emission be 1.5 Gt/yr Actions to stabilize immediately are only the first steps Assuming the wedge strategy is adopted and global are held constant at near today s value ( Gt/yr) until 2054, CO 2 will reach ~ 40ppm at that time. Phase II: To stabilized at ~500ppm, global of CO 2 must then decline rapidly to about 1.5 Gt/year by ~2100, or to about 20% of today s As a reference frame, if the world shared fossil fuels equally, then in 2100 the US would be able to emit only about 3% of the CO 2 it now emits. At the same time, global energy production must increase many-fold greater than today (increased population and economic growth --> increased energy demand)