1. 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 Key figures: Included here; Expected to be able to interpret them.

2. Evidence of Warming

3. Long term orbital “Milankovich” cycles Northern Southern summer in north Southern winter Seasons now & TILT oscillation ~41k years & ECCENTRICITY oscillation ~100 k years

4. Science 2007 (DOI: 10.1126/science.1136843) Sea level rise particularly underpredicted (note measurement change at 1993: tide gauges -> satellite data)

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

6. 4. Troposphere and Stratosphere Calculated Radiation-Convection temperature profiles

7. More complete radiation balance

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

9. SURFACE WARMING STRATOSPHERE COOLING SPACE EARTH Greenhouse effect strengthens as earth warms (feedback) 1960 2000 rise to restore balance with space larger surface rise results

10. Figure TS.5 Anthropogenic Radiative Forcings IPCC AR4 2007

11. Response and Feedback

12. 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

13. 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.

14. Modelling: Basic Physics …

15. 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 20 th climate trends Predictability General claim: Weather chaotic (beyond ~two weeks) but wider/longer scale climate changes relatively predicable. Exploit: Expensive AOGCM calculations -> calibrate simpler simulations -> mass produce climate predictions for different future scenarios

16. 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. a range of plausible assumptions 2. Population continues to increase. A2: very heterogeneous world (“business as usual”) B2: lower growth rate; emphasis on local solutions (smart but laissez-faire) B1: info & service economy; sustainability & global sol’ns. B2 Climate modelling B2 Climate Prediction EU target

17. 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; (?2008: faster?) (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).

18. (ca 2002)

19. 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. 2006 UK publishes emission reductions legally binding in domestic law

20. World emissions trends: growth vs mitigation commmitment UK CO2 emissions

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

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

23. Geological storage of carbon dioxide 736 Gt in North Sea alone (DTI)

24. Cost-benefit analysis Discounting Payback

25. 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 Key figures: Included here; Expected to be able to interpret them.