1. coupled Ocean- Atmosphere General/Global Circulation Models ~100km horizontal res’n; Finer (~2) for ocean than atmosphere. ~20 layers atmosphere; ~20 layers ocean. Geography inevitably coarse. “Regionalisation”: redo simulation of one region only (e.g. Europe) matched onto cruder global simulation

2. Basic Physics …

3. Features and processes Moist processes: Evaporation & condensation: clouds and latent heat Radiation processes, light and IR Sub-resolution convection -> effective viscosity & dispersion Surface changes, e.g. of albedo and roughness Atmosphere-Surface exchange: heat, vapour, liquid, momentum

4. Turbulence <<10km: three dimensional >>10km: two dimensional Sub-resolution convection -> effective viscosity & dispersion

5. State of art ca 1997 Major Volcanos -> Major volcanic eruptions are a visible and predictable perturbation on the climate.

6. Figure TS.23 IPC 2007 “Greenhouse gas forcing has very likely [90%] caused most of the observed global warming over the last 50 years.” IPCC 2007 ….likely [67%].. IPCC 2001

7. IPCC 2007 Previous predictions … correct to show wide error bars

8. =Temperature rise from doubling CO 2 (equivalent) IPCC2007

9. 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 20 th climate trends Exploit: Expensive AOGCM calculations -> calibrate simpler climate simulations -> mass produce climate predictions for different future scenarios

10. 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. not predictions, but 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

11. The global climate of the 21st century IPCC S/PM 2001

12. Figure TS.28 IPCC 2007: Scenario -> OAGCM -> Climate prediction

13. Figure 10.4 IPCC 2007

15. Observed and projected changes in extreme weather and climate events. IPCC S/PM 2001

17. OAGCM predictions (sample) B2 annual mean change of the temperature (colour shading) and its range (isolines) (Unit: °C) for SRES A2 and B2.A2B2 period 2071 to 2100 relative to 1961 to 1990 IPCC2001

18. Projected temperatures