1. IPCC Working Group I: The Physical Science Basis Thomas Stocker Co-Chair Working Group I University of Bern, Switzerland IPCC AR5 "The Physical Science Basis": Challenges, Structure and Timetable

2. Working Group I Contribution to the IPCC Fifth Assessment Report IPCC Expert Meeting on Assessing and Combining Multi Model Climate Projections Warming in the climate system is unequivocal, as is now evident from observations.... Most of the observed increase in global averaged temperature... is very likely due to... increase in GHG concentrations. Continued GHG emissions... would induce many changes... that would very likely be larger than those observed... IPCC (2007):

3. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable Overview of topical groups of chapters in WGI of AR5:  Introduction Chapter 1  Observations and Paleoclimate Information Chapters 2, 3, 4, 5  Process Understanding Chapters 6, 7  From Forcing to Attribution of Climate Change Chapters 8, 9, 10  Future Climate Change and Predictability Chapters 11, 12  Integration Chapters 13, 14 The full Outline of WGI is available on www.ipcc.unibe.ch

4. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable The full Outline of WGI is available on www.ipcc.unibe.ch New features in WGI AR5

5. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable The full Outline of WGI is available on www.ipcc.unibe.ch New features in WGI AR5

6. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable New features in WGI AR5 The full Outline of WGI is available on www.ipcc.unibe.ch

7. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable The full Outline of WGI is available on www.ipcc.unibe.ch New features in WGI AR5 Annex I: Atlas of Global and Regional Climate Projections: Editorial Team, Review Editor Team, Advisory Board

8. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable Jan-Mar 12Nomination of CLAs, LAs, and REs by IPCC Focal Points MaySelection of CLAs, LAs, and REs by WGI Bureau NovLA1 Kunming, China Mar-JunCompletion of zero-order draft, and review JulLA Meeting 2 Nov-FebCompletion of first-order draft, and review AprLA Meeting 3 Jul 31cut-off for submitted papers Aug-NovCompletion of second-order draft, and review JanLA Meeting 4 Mar 15cut-off for accepted papers JunCompletion of final draft Jun-Aug Final government distribution and review of SPM Sep 16-19WGI AR5 Approval Plenary 2010 2011 2012 2013 Timetable of the WGI Contribution to AR5:

9. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable Jan-Mar 12Nomination of CLAs, LAs, and REs by IPCC Focal Points MaySelection of CLAs, LAs, and REs by WGI Bureau NovLA1 Kunming, China 2010 Timetable of the WGI Contribution to AR5: Your expertise in AR5 is needed: Please contact your IPCC Focal Point

10. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable Challenges:  Amount of material (literature, simulations) and the burden to the scientific community  Significantly broader model diversity and likely increase in uncertainty  Communication of uncertainties: what is known, what is emerging  More cross-WG cooperation retaining full coherency  Maintain the highest standards under increased pressure and expectations in a highly politicized environment  Transparency, Rigorosity, Comprehensiveness, Robustness

11. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable What do you require of WCRP ? 1.Clouds & Aerosols: Processes and Sensitivities 2.Decadal Prediction: Evaluation and Verification 3.Multi-Model Ensembles using Earth System Models 4.Regional Climate Change: D&A and Projections 5.Sea Level Rise and Ice Sheet Instabilities 6.Geoengineering WCRP organizes and catalizes the science, defines priorities, launches big programs, oversees multi-year international research

12. Working Group I Contribution to the IPCC Fifth Assessment Report The Physical Science Basis: Challenges, Structure, Timetable Jan-Mar 12Nomination of CLAs, LAs, and REs by IPCC Focal Points MaySelection of CLAs, LAs, and REs by WGI Bureau NovLA1 Kunming, China 2010 Timetable of the WGI Contribution to AR5: Your expertise in AR5 is needed: Please contact your IPCC Focal Point Information: wg1@ipcc.unibe.ch