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CE 107: Climate-Change Mitigation Lecture #1: Overture 24 August 2012 Bill Nazaroff CEE Dept UC Berkeley California, USA Cartoon: Tokoro Yukiyoshi Issues • • • • Is anthropogenic climate change happening? What can we expect for the future under BAU*? What can we about it? What are we doing about it? *BAU = “business as usual” Atmosphere affects Earth’s energy balance Source: IPCC, Climate Change 2007: The Physical Science Basis, Ch Atmosphere naturally warms the earth Global average surface temperature is increased by 35 K because atmospheric gases absorb in the infrared and are transparent in the visible Atmospheric CO2 levels are rising CD Keeling (1928-2005) source: mlo145e_thrudc04.pdf Fossil-fuel use: A major cause for rising CO2 GtC = billion tonnes of carbon Consequences: Increased radiative forcing Source: IPCC (2007) — Summary for Policymakers What will happen as a result? WS Broecker (1931-), Columbia University Broecker (2000) has likened our release of greenhouse gases to the atmosphere to poking an angry beast with a stick! We’re not sure what will happen, but chances are it won’t be good! Source: WS Broecker, Annual Review of Energy and the Environment 25, 1-19, 2000 Where are we headed under BAU? (IPCC) Source: IPCC, Climate Change 2007 — The Physical Science Basis Global warming in time and space (IPCC) Source: IPCC, Climate Change 2007 — The Physical Science Basis 10 Projected climate-change impacts: California • Public health — Degraded air quality; more heat stress • Water — Strained water supplies; diminished hydropower production; loss of winter recreation • Agriculture — Expanding ranges of weeds; increased threats from pests and pathogens • Forests & landscapes — Increasing wildfires; shifting vegetation; declining forest productivity • Rising sea level — Increased coastal flooding; shrinking beaches Source: Our Changing Climate — Assessing the Risks to California (http://www.climatechange.ca.gov) 12 Mitigation? Stabilize atmospheric CO2 levels Atmospheric CO2 levels: preindustrial ~ 280 ppm today ~ 390 ppm Emission rates: today ~ GtC/y 2100, BAU ~ 20 GtC/y 2100, WRE450 ~ GtC/y Need 7x decrease from BAU • Aggressive measures required to stabilize at 450 ppm CO2 • Still may not suffice to prevent serious environmental damage 13 Per-capita fossil-C emission targets Notes: (1) Lines labeled with atmospheric CO2 stabilization levels (ppm); (2) Population projection peaks at billion in 2070 14 Pause: Comic relief The picture’s pretty bleak … The world’s climates are changing, the mammals are taking over, and we all have a brain about the size of a walnut - Gary Larson The Far Side copyright 1985 Universal Press Syndicate 15 What to do? A supply-side proposition… Space-based power systems Mega-scale renewables “Primary power consumption today is ~ 12 TW, of which 85% is fossil-fueled Stabilization at 550, 450, and 350 ppm CO2 … require emission-free power by mid-century of 15, 25, and > 30 TW, respectively.” Source: MI Hoffert et al., Science, 298, 981-987, 2002 Nuclear fusion 16 Alternative prescription: Stabilization triangle Source: http://www.princeton.edu/pr/news/04/q3/0812-carbon/figure1.jpg 17 Stabilization wedges: Portfolio approach • • • • Referenced to “business as usual.” Grow from today to GtC/y by 2055 Saves 25 GtC during 2005-2055 Need wedges to avoid l a u CO2 rise to 550 ppm s u s a s • wedges = 175 GtC es in s bu stabilization trajectory (550 ppm) Source: S Pacala and R Socolow, Science, 305, 968-972, 2004 18 Wedges — End use, supply, C mgmt • • • • • • Energy efficiency & conservation (4 options) Renewable electricity & fuels (4) Fuel shift (1) Nuclear fission (1) CO2 capture and storage (3) Forests & agricultural soils (2) 19 Stabilization wedges: Good news/Bad news • Good: 15 candidate wedges identified; only needed • Good: Technology already exists for each wedge: only scale-up required • Bad: Each wedge will require substantial societal effort • Bad: Stabilization at 550 ppm will not prevent damage • Bad: Need to save 350 GtC vs BAU during 2050-2100 20 Mitigation: What else might be considered? • Behavioral changes affecting consumption: A conservation ethic — “sufficiency” • Climate geoengineering John Muir (1838-1914) Edward Teller (1908-2003) 21 Conservation ethic: Who advocates for it? “We don't need bigger cars or fancier clothes We need self-respect, identity, community, love, variety, beauty, challenge, and a purpose in living that is greater than material accumulation The ads tell us that bigger cars and fancier clothes will bring us those nonmaterial benefits, but of course the ads lie By selling us things that promise to fill our inner emptiness but ultimately don't, they set us up to want more, and more, and more You can never get enough of what you don't really need.” Donella (Dana) Meadows (1941-2001) Source: D Meadows, “What does sustainability mean? (http://www.sustainabilityinstitute.org/) 23 April 1992 22 Climate geoengineering: Some concepts Injection of sulfate particles into the stratosphere Space-based solar “parasol” sources: UCRL-JC-128715, LLNL, Livermore, California, August 1997; Science, 298, 981-987, 2002 23 Climate geoengineering: Two views “Humanity may inevitably grow into active planetary management, yet we would be wise to begin with a renewed commitment to reduce our interference in natural systems rather than to act by balancing one interference with another.” — D Keith, Ann Rev Energy Environ 25, 245, 2000 “Given the grossly disappointing international political response to the required greenhouse gas emissions … research on the feasibility and environmental consequences of climate geoengineering … should not be tabooed.” — PJ Crutzen, Climatic Change 77, 211-219, 2006 24 What are we doing about CCM? (California) • Executive order S-3-05: Reduce emissions – – – – By 2010 to 2000 levels By 2020 to 1990 levels (*) By 2050 to 80% below 1990 levels (*) Despite major population growth (to 50-70 million by 2050) http://www.climatechange.ca.gov/ (*) Not yet clear that the goals will be achieved 25 Toward climate sustainability • Climate protection is attainable • Requires commitment, persistence & diligence • Portfolio approach is essential • Ingredients – – – – Efficiency Low-C energy Carbon management Sufficiency • Recipe for action: Do what you can, wherever you are; then more Repeat Figure source: http://www.everyjoe.com/articles/files/2009/06/cope-hope-flagpole-english-low-res.jpg 26