Thomas Stocker Physics Institute Oeschger Centre for Climate Change Research University of Bern, Switzerland Climate Change: Making the Best Use of Scientific Information

How hot was the summer 2011 ? European summers of the past 500 years:  2011 was not the hottest summer  The 5 coldest occurred before 1924  The 5 hottest occurred after 2001 Climate Change: Making the Best Use of Scientific Information

1.Climate Change: A Naturally Difficult Topic 2.Four Challenges in Communication 3.The Specific Mandate of IPCC 4.Conclusions

Climate change: A naturally difficult topic

Space scales:10 –6 m m Time scales:10 –6 s s Climate change: A naturally difficult topic

 There are no „desk-top“ experiments  Where is the smoking gun?  Climate is always changing  We experience weather, not climate  Yet, everybody has an opinion Climate change: A naturally difficult topic

The Earth is the centre of the universe Climate change: A naturally difficult topic The Earth orbits around the Sun Space and time are absolute dimensions Matter and energy modify space-time Nature is deterministic Uncertainty principle and deterministic chaos Climate changes are due only to natural processes Humans are modifying global climate Old Paradigm Scientific Fact ?

Climate Change: Making the Best Use of Scientific Information 1.Climate: A Naturally Difficult Topic 2.Four Challenges in Communication 3.The Specific Mandate of IPCC 4.Conclusions

Four challenges in communication Challenge #1: A widening gap Science Literacy Communication Literacy Scientists Public Science Journalists

Four challenges in communication Challenge #2: Many sources of information  Scientific publications  Lectures and presentations by scientists  International Assessments  Media: Press, TV, Radio, Movies  Social Media: Facebook, Blogs  Science popularizations  Position papers by „Think Tanks“

Four challenges in communication Challenge #3: Information with Uncertainty  How to determine uncertainty?  How to display uncertainty?  How to formulate uncertainty?

Four challenges in communication (Mastrandrea et al., 2011) Challenge #3: Information under Uncertainty How to determine uncertainty?

1.1 to 6.4 °C Four challenges in communication (IPCC, 2007, Fig. SPM-5) Challenge #3: Information under Uncertainty How to display uncertainty?

Four challenges in communication Challenge #3: Information under Uncertainty How to formulate uncertainty? level of agreement amount and quality of evidence confidence virtually certain  99% very likely  90% likely  66% unlikely  33%... Qualitative: Quantitative: quantified likelihood

Do we speak language or jargon? Scientific TermPublic MeaningBetter Choice positive feedbackgood response, praiseself-reinforcing cycle theoryhunch, speculationscientific understanding uncertaintyignorancerange biasdistortion, political motiveoffset from observation schemedevious plotsystematic plan (Somerville and Hassol, 2011) Challenge #4: Precise but non-technical language

Do we speak language or jargon? Scientific TermPublic MeaningBetter Choice positive feedbackgood response, praiseself-reinforcing cycle theoryhunch, speculationscientific understanding uncertaintyignorancerange biasdistortion, political motiveoffset from observation schemedevious plotsystematic plan (Somerville and Hassol, 2011) Challenge #4: Precise but non-technical language

Do we speak language or jargon? Scientific TermPublic MeaningBetter Choice positive feedbackgood response, praiseself-reinforcing cycle theoryhunch, speculationscientific understanding uncertaintyignorancerange biasdistortion, political motiveoffset from observation schemedevious plotsystematic plan (Somerville and Hassol, 2011) Challenge #4: Precise but non-technical language

Climate Change: Making the Best Use of Scientific Information 1.Climate: A Naturally Difficult Topic 2.Four Challenges in Communication 3.The Specific Mandate of IPCC 4.Conclusions

The specific mandate of IPCC Principles Governing IPCC Work (1998, 2003, 2006)

The specific mandate of IPCC Working Group I: The Physical Science Basis Working Group II: Climate Change Impacts, Adaptation, and Vulnerability Working Group III: Mitigation of Climate Change Authors / RE

The specific mandate of IPCC

Science Community Governments scoping of outline of assessment approval of outline nomination and selection of experts 0-Order Draft (ZOD) informal review 1-Order Draft(FOD) expert review government review2-Order Draft(SOD)expert review Final Draft (FGD) government review approval of SPM and acceptance of report Lead Authors of Working Group election of WG Sept 2013

Climate Change 2013 Elements of an Assessment Report Report 14 Chapters, Annexes, Supplementary Material target 600 pages (excl. Figures, Tables, and Refs.) Summary for Policymakers target 15 pages (total) Technical Summary target 70 pages (incl. Figures) Synthesis Report all WGs contribute (target 50 pages excl. Figs.) The specific mandate of IPCC Working Group IWGII WGIII

Warming in the climate system is unequivocal,... (IPCC, 2007, Fig. SPM-3) A unique way of scientific communication IPCC (2007):

Continued GHG emissions [..] would cause further warming and induce many changes [..] that would very likely be larger than those observed [..]. (IPCC, 2007, Fig. SPM-6,7) IPCC (2007): A unique way of scientific communication

[..] a 1-in-20 year hottest day is likely to become a 1-in-2 year event [..] in most regions [..]. IPCC SREX (2011): (IPCC, 2011, Fig. SPM-4a) A unique way of scientific communication

Climate Change: Making the Best Use of Scientific Information 1.Climate: A Naturally Difficult Topic 2.Four Challenges in Communication 3.The Specific Mandate of IPCC 4.Conclusions

Conclusions  Communication on climate change faces special challenges in a highly politicized environment;  The clearer the scientific evidence for man-made climate change becomes, the more vocal are detractors, often operating as merchants of doubt;  Intergovernmental assessments are essential to deal with problems of global impact;  IPCC assessments produce the most effective scientific information if they are rigorous, robust, transparent and comprehensive.

Communicate the possible futures Make the choice