Climate Change Scenarios and their Evolution in the IPCC Assessment Reports

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1 Climate Change Scenarios and their Evolution in the IPCC Assessment Reports Tarek Sadek Water Resources and Climate Change Officer Sustainable Development and Productivity Division UN-ESCWA

2 Outline 1.Climate 2.Global Climate Trends 3.The Role of GHG s 4.Global Emissions Scenarios SA90 IS92 SRES RCP s

3 Climate: What defines it Biophysical systems: Interactions between: Physical systems: atmosphere, oceans, surface Biological systems: trees, plankton Socio-Economic systems: Human economic interactions Their resulting actions on various biophysical systems.

4 Major natural and anthropogenic processes and influences on the climate system addressed in scenarios. RH Moss et al. Nature 463, (2010) doi: /nature08823

5 GCM: Global Climate Trends The Climate: Before mid-20 th Century: Oscillate in a relatively stable manner, with little variation from cycle to cycle. After mid-20 th Century: Warming from oscillation to oscillation While the weather of a given day cannot be predicted in the far future, the change in prevailing future climate trends can be forecasted with relative accuracy Source: Gleckler, P. J.; Taylor, K. E.; Doutriaux, C.; 2008: Performance Metrics for Climate Models, Journal of Geophysical Research, Vol. 113.

6 The Effect of GHG s Natural Effects + Human GHG Emissions Only Natural Effects: No Human GHG Emissions REF: Hegerl, G.; Zwiers, F.; 2011: Use of models in detection and attribution of climate change, Article first published online: 26 May 2011, Wiley Interdisciplinary Reviews: Climate Change, Vol. 2 Issue 3. Meehl, G.A.; Stocker, T.F.; Collins. W.D.; Friedlingstein P.; Gaye, A.T.; Gregory, J.M.; Kitoh, A.; Knutti, R.; Murphy, J.M.; Noda, A.; Raper, S.C.B.; Watterson, I.G.; Weaver A,J.; Zhao, Z.C.; 2007: Global climate projections - climate change 2007: The Physical Science Basis, Contribution of Working Group I to the fourth assessment report of the Intergovernmental Panel on climate change (IPCC). Cambridge University Press, Cambridge, UK.

7 GHG s and Radiative Forcing GHG W/m 2

8 Timeline highlighting some notable developments in the creation and use of emissions and climate scenarios RH Moss et al. Nature 463, (2010) doi: /nature08823

9 Timeline highlighting some notable developments in the creation and use of emissions and climate scenarios (cont d) RH Moss et al. Nature 463, (2010) doi: /nature08823

10 IPCC Sequential approach This process caused delays. SRES used for first time in TAR in 2001 but not until IPCC published the AR4 in 2007 when more complete set of SRES-driven climate scenarios assessed by IPCC. RH Moss et al. Nature 463, (2010) doi: /nature08823

11 1990 IPCC SA90 Emission Scenarios - FAR Scenario A (Business as usual) Coal intensive energy supply Deforestation continues Agricultural emissions are uncontrolled Scenario B Lower carbon fuels (e.g. natural gas) Increased efficiency Deforestation is reversed Scenario C A shift towards renewable and nuclear energy in second half of the next century Agricultural emissions limited. Scenario D A shift towards renewable and nuclear energy in first half of the next century Carbon dioxide emissions are reduced to 50% of 1985 levels by middles of next century

12 The scenarios show the global, energy related and industrial CO2. They range from very high emissions of 35.8 GtC/year to very low emissions of 4.6 GtC/year by 2100 (the shaded area). Dealt with uncertainties in economic growth, population and technology. These scenarios were used in the Third Assessment Report (TAR) IPCC IS92 Emission Scenarios TAR

13 2000 IPCC Special Report on Emission Scenarios (SRES) AR4 Work forward : From a set of socio-economic changes (i.e. a wide range of driving forces) Complemented by storylines or narratives of the future which facilitated interpretation of the scenarios. Produced through an open process involving many modeling teams. The IS92 and SRES scenarios assumed there were no policy actions to mitigate climate change.

14 The RCP Emission Scenarios Selection of four Representative Concentration pathways No assumptions on socioeconomic projections: The net radiative forcings resulting from those assumptions must arrive at a value in W/m 2 Related to a given concentration of CO 2 -Equivalent Radiative Forcing GHG Concentration (CO2-Equivalent) Pathway Shape RCP8.5 >8.5 W/m2 in Rising after 2100 RCP6 RCP4.5 RCP3-PD ~6 W/m2 at stabilization after 2100 ~4.5 W/m2 at stabilization after 2100 peak at ~3W/m2 before 2100 and then decline 850 Stabilization after Stabilization after Peak at 2100 and decline afterwards

15 Representative concentration pathways (RCP s) RH Moss et al. Nature 463, (2010) doi: /nature08823

16 RCP Emission Scenario Families Focus = Implications of Radiative Forcing CO 2 e stabilizes after 2200 CO 2 e: 1370 ppm, rising after 2100 CO 2 e stabilizes after 2100 CO 2 e: 850 ppm CO 2 e: 650 ppm CO 2 e stabilizes after 2100 CO 2 e: 490 ppm, CO 2 e peaks before 2100 CO 2 e:decreasing after 2100 REF: Meinshausen, M.; Smith, S.J.; Calvin, K.; Daniel, J.S.; Lamarque, J-F.; Matsumoto, K.; Montzka, S.; Raper, S.C. B.; Riahi, K.; Thomson, A.; Velders, G.J.M;. van Vuuren, D.P.; (submitted): The RCP Greenhouse Gas Concentrations and their Extensions from 1765 to 2500, Climatic Change..

17 Impact of mitigation policy measures..

18 The parallel process RCP s not associated with unique socioeconomic or emissions scenarios RH Moss et al. Nature 463, (2010) doi: /nature08823

19 Thank you