1. Demystifying global warming Some basic observations for international students JN Birchall ‘Global Warming Update’,

2. The greenhouse effect Making predictions … and some possible surprises What are the predictions? Past trends in climate Debates on the ‘climate change’ problem Policy advice Supplementary materials: Exercise on observations of recent climate change Information sources and ideas

3. The greenhouse effect

5. More gas! Concentrations of greenhouse gases are higher now than at any time for the past 500,000 years 381 ‘Natural’ CO 2 conc.

6. Making predictions How are predictions made? What are the sources of uncertainty? Can we trust climate models? What factors do models include? Are there major sources of uncertainty not accounted for?

7. Basis of climate change predictions Socio-economic scenarios Greenhouse gas emissions Greenhouse gas concentrations Predicted temperature change Uncertainty V. large Large Moderate

8. CO 2 in SRES scenarios (SRES, 2000) IPCC 2001 http://www.grida.no/climate/ipcc_tar/wg1/figspm-5.htmhttp://www.grida.no/climate/ipcc_tar/wg1/figspm-5.htm Activity: Explore the IPCC scenarios and discuss their relative likelihood and/or policies which would see them fulfilled

9. GCM structure Climate Research Unit, UEA

10. One way to test a climate model: Comparing observed climate with modeled climate IPCC (2001): Figure 8.2 lower left

11. Major change to predictions from similar GHG scenarios (1996 cf. 1990)

12. Some possible surprises…. Methane hydrates (oceans 9500 Gt, permafrost 400 Gt) Carbon cycle: strength of ocean and terrestrial ‘sinks’ Ocean circulation: the ‘thermohaline conveyor’

13. NASA Earth Observatory http://earthobservatory.nasa.gov/Newsroom/NasaNews/2001 /200112106303.html Activity: If 10% of methane hydrates were released, how does this compare with anthropogenic sources? Methane hydrates stored in oceans and permafrost

14. Woods Hole research Center (2004) http://www.whrc.org/carbon/missingc.htm Will natural sinks persist? Activity: Evaluate the impact of the decrease/loss of the oceanic and/or terrestrial carbon sink on global carbon flux

15. Temperature change following shutdown of the North Atlantic conveyor (Vellinga and Wood, 2002. Climatic Change 54: 251-267) Likelihood of decline in MOC - from a survey of scientists in the RAPID programme http://www.soc.soton.ac.uk/rapi d/sci/pdf/ann_mtg_survey.pdf Activity: To what extent should adaptation policy be formed by the possibility of North Atlantic conveyor shutdown?

16. What are the predictions? Range Regional patterns Changing ideas Seasonality

17. IPCC(2001) Fig 9.14

18. IPCC (2001) Fig 9.10d. Multimodel ensemble annual temperature change 2071-2100 - 1961-1990 Shading - temp change, Blue lines - range o C, green - mean change/mean sd

19. IPCC (2001) Fig 9.11d. Multimodel ensemble annual precipitation % change 2071-2100 - 1961-1990 Shading - mean change, red lines - range, green - mean change/mean sd

20. IPCC reports - evolving predictions of climate change YearGlobal tempSea level rise o Crise cm 19903.0 (1.5-4.5)65 19952.0 (1.0-3.5)48 (13-94) 20011.4-5.89-88 No best guesses

21. Seasonality can be more important than net change - e.g. UK precipitation (UKCIP02) www.ukcip.org.uk 2020s 2050s 2080s

22. Past trends in climate Is there a trend in global climate change? How do current temperatures compare with those in the past? Frost fair on the River Thames (1814) How much has global temperature risen over the past 100 years?

23. 2000 1994 1989 Timing of IPCC report preparation Activity(s): Are current trends in climate consistent with predictions for the future? See file.

24. Global temperature reconstructions for last 1000 years: are we now outside the range of “natural” variability? 1st IPCC report (1990) Note: no T scale “no” 3rd IPCC report (2001) based partly on using multi-proxy palaeoclimate data - the “hockey-stick” curve probably “yes”

25. Is the hockey stick still valid? Multiple “spaghetti curves” now published larger changes than original hockey stick still show the late C20th as the warmest period of the last millennium how critical is this anyway to the case for human-induced warming?

26. DEBATES There is genuine broad (although not 100%) consensus in the climate science community on main issues Argument, scepticism and hypothesis testing are at the heart of good science Publication of research, review and quality control are essential in this process

27. Arguments of ‘climate sceptics’ Trends. There is no significant trend in global temperature (e.g. urban heat island effect, geographic coverage of data) Attribution. Human activities are not responsible for observed trends Impacts. The negative impacts of predicted climate change are over- estimated; cost-benefit analysis does not support mitigation action

28. Trends e.g. Urban heat island Sources: http://antwrp.gsfc.nasa.gov/apod/ap040822.html http://data.giss.nasa.gov/gistemp/2005/ Activity: Compare temperature records from urban and rural areas in the UK – is there a systematic difference and how big is it?

29. Attribution Observed changes are: within natural variability due to other effects (e.g. solar variability) IPCC (2001) Figure 4 from SPM. Model outputs using natural (solar, volcanic) and anthropogenic (GHGs, aerosols) climate forcing

30. Impacts sceptics The costs of mitigating climate change are greater than the benefits gained from adapting to change Best exemplified by Bjorn Lomborg in ‘the skeptical environmentalist ’ Activities: How accurate are estimates of costs and benefits likely to be? Economic costing does not include costs to natural systems – does this matter?

31. Science, consensus and debate Consensus Sceptic Supporter Contrasting reading - Fact vs fiction? Is the distinction clear? Activity: Take extracts from the above (or use www sites) and identify differences in style, language, use of documentation, nature of documentation

32. International policy – is scientific advice followed?

33. International policy Scientific advicePressure groups (±)Media and public opinion International policy Government delegates Acceptance in national governments Government policy.. and action Activity: Follow one of the COP meetings linked to the UN Framework Convention on Climate Change www.unfccc.org

34. What are ‘desirable’ levels of future climate change? Defined by: Global temperature (+2 o C?) Global emissions (2.5 Gt C fossil fuels pa?) Atmospheric concentration (450-550 ppm CO 2 ?) Timescale e.g. UK RCEP (2002) Suggest 60% reduction on 1990 CO 2 emissions by 2050 for UK Compare with: –Kyoto target of c. 5.2% by 2008-2012 for Annex 1 countries –UK Government target of 20% by 2010 (and may hit 10%....)

35. Use the graph below from the RCEP Energy report as a starting point for debating questions such as: Which parts of the world are the biggest contributors to climate change? Should targets for reductions be based on current total contributions, per capita emissions or perhaps emissions per GDP?