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PX272 revision summary

Main topics: Evidence of Warming Atmospheric Greenhouse effect Forcing and Feedbacks Scenarios and Modelling Consequences of Warming Political Actions Mitigation Options Key Revision material: J Horton Review article Assignments + f/back, particularly 2-5 Powerpoint slides on web.

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PX272 revision summary

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  1. Main topics: • Evidence of Warming • Atmospheric Greenhouse effect • Forcing and Feedbacks • Scenarios and Modelling • Consequences of Warming • Political Actions • Mitigation Options • Key Revision material: • J Horton Review article • Assignments + f/back, particularly 2-5 • Powerpoint slides on web PX272 revision summary • Key figures: • Included here; • Expected to be able to interpret them.

  2. Evidence of Warming

  3. 2. Key Temperatures Atmospheric Greenhouse effect 1. Global Energy Balance

  4. 4. Troposphere and Stratosphere CalculatedRadiation-Convection temperature profiles

  5. 3. Infra-red emission spectrum (over sunny mediterranean)

  6. Surface warmingBUTstratosphere cooling

  7. 2005 Global mean forcing 2000 vs 1750 IPCC S/PM 2001

  8. Response and Feedback

  9. Ocean Circulation Feedback • Huge heat capacity • - delays warming • Circulation driven by: • temperature difference • salinity difference • rotation of earth • redistributes regionally:more winter heat to NW Europe from ocean transport than from sun • global heat redistribution still dominated by atmosphere

  10. Biological Feedbacks Negative λ: some plants grow better at increased CO2  levels, causing an increase in the amount absorbed Positive λ: Increased temperature  increased respiration rates (especially for microbes in soil), hence increased CO2  output.   climate stress  reduced tree growth and die-back.

  11. Modelling: Basic Physics …

  12. Predictability General claim: Weather chaotic (beyond ~two weeks) but wider/longer scale climate changes relatively predicable. Evidence: Correlation of ice ages with Milankovitch cycles (of earth orbit) Successful replication of response to largest sudden terrestrial perturbations: Volcanoes El Nino changes in ocean circulation Replication of 20th climate trends Exploit: Expensive AOGCM calculations -> calibrate simpler simulations -> mass produce climate predictions for different future scenarios

  13. B2 Climate Prediction EU target Climate modelling Special Report on Emissions Scenarios • 1. Population peaks mid century. • A1: technology-led economy, • F fossil fuels vs ( B “balanced” ) vs T non-fossil fuelled. B2 B1: info & service economy; sustainability & global sol’ns. 2. Population continues to increase. A2: very heterogeneous world (“business as usual”) B2: lower growth rate; emphasis on local solutions (smart but laissez-faire) a range of plausible assumptions

  14. Consequences of Warming (see assignment 5) Sea level rise • 0.5-1m to 2100, majority thermal expansion, much already inevitable • Greenland ice  7m now seriously possible, but ~1000 yrs. • W Antarctic  6m, presumed 100’s of years;(E Antarctica  60m but thought stable) Coastal (especially delta) populations directly vulnerable; loss of coastal wetland threatens fish breeding etc. Climate more extreme • Increased global precipitation but more uneven by time (e.g. fewer moist days) and space (dry get drier, wet get wetter). • More drought AND more flood • More and stronger storms (atmosphere as stronger heat engine) Shift of agricultural productivity • High northern latitudes gain, tropics lose. Possible Atlantic Thermohaline shut-off • NW Europe would lose its major winter heat source (>sun).

  15. Political Actions 1988: Intergovernmental Panel on Climate Change  Assessment reports 1990 1997 2001 2007 1992: Framework Convention on Climate Change (FCCC), signed by over 160 countries , UN conf Rio 1992, effective 1994. 1997: Kyoto Protocol (legislation under the FCCC)first target: average emissions 2008–2012 below 1990 levels by 5- 8%flexibility: Joint Implementation (cheapest savings) Clean Development Mechanism (avert new emissions) Emissions Trading 2005 Ratification threshold of KP achieved by Russia ratifying, but NOT the USA or Australia. Europe: emissions trading at ~ €25 / tCO2 ~ €100 / tC . Outside Kyoto: “Asia-Pacific 6” Australia, India, Japan, PR China, S Korea, USA.

  16. Mitigation options:Wedges One “wedge”: reduce the carbon emission rate in 2055 by about 1 GtC/year, “Avoiding Dangerous Climate Change” CUP 2006

  17. Leading wedges (one 2006 opinion) Technically feasible? CO2 capture at power station CO2 capture at H2 plant CO2 capture at coalsynfuels plant Nuclear power Wind power Already happenning? More efficient vehicles Less vehicle use More efficient buildings More efficient power plants Replace coal by gas Societally Challenging on the scale required? Photovoltaic base power Wind H2  cars Biomass fuel Reverse forest loss Conservation soil management

  18. Main topics: • Evidence of Warming • Atmospheric Greenhouse effect • Forcing and Feedbacks • Scenarios and Modelling • Consequences of Warming • Political Actions • Mitigation Options • Key Revision material: • J Horton Review article • Assignments + f/back, particularly 2-5 • Powerpoint slides on web PX272 revision summary • Key figures: • Included here; • Expected to be able to interpret them.

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